US20080218867A1 - Image display device and portable terminal device - Google Patents
Image display device and portable terminal device Download PDFInfo
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- US20080218867A1 US20080218867A1 US12/071,340 US7134008A US2008218867A1 US 20080218867 A1 US20080218867 A1 US 20080218867A1 US 7134008 A US7134008 A US 7134008A US 2008218867 A1 US2008218867 A1 US 2008218867A1
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- image display
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells
- G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
- G02F1/1333—Constructional arrangements; Manufacturing methods
- G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
- G02F1/133526—Lenses, e.g. microlenses or Fresnel lenses
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B30/00—Optical systems or apparatus for producing three-dimensional [3D] effects, e.g. stereoscopic images
- G02B30/20—Optical systems or apparatus for producing three-dimensional [3D] effects, e.g. stereoscopic images by providing first and second parallax images to an observer's left and right eyes
- G02B30/26—Optical systems or apparatus for producing three-dimensional [3D] effects, e.g. stereoscopic images by providing first and second parallax images to an observer's left and right eyes of the autostereoscopic type
- G02B30/27—Optical systems or apparatus for producing three-dimensional [3D] effects, e.g. stereoscopic images by providing first and second parallax images to an observer's left and right eyes of the autostereoscopic type involving lenticular arrays
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04M—TELEPHONIC COMMUNICATION
- H04M1/00—Substation equipment, e.g. for use by subscribers
- H04M1/02—Constructional features of telephone sets
- H04M1/0202—Portable telephone sets, e.g. cordless phones, mobile phones or bar type handsets
- H04M1/0206—Portable telephones comprising a plurality of mechanically joined movable body parts, e.g. hinged housings
- H04M1/0208—Portable telephones comprising a plurality of mechanically joined movable body parts, e.g. hinged housings characterized by the relative motions of the body parts
- H04M1/0214—Foldable telephones, i.e. with body parts pivoting to an open position around an axis parallel to the plane they define in closed position
Definitions
- the present invention relates to an image display device capable of displaying an image toward a plurality of points of view and a portable terminal device mounted with this image display device.
- the three-dimensional image display device displays parallax images for the right eye and left eye, and a viewer looking with both eyes at the images differentiated between right and left can perceive a three-dimensional image.
- Three-dimensional image display systems can be broadly classified into two types, one using glasses and the other using no glasses.
- the former can be further subdivided into the anaglyph type utilizing differences in color and the polarization glass type. But both of them have the essential problem that the viewer must use glasses. For this reason, the latter, using no glasses, has become more popular, and this can be sub-classified into the parallax barrier type and the lenticular lens type.
- FIG. 12 is an optical model diagram illustrating a three-dimensional display method by the parallax barrier system.
- a parallax barrier 105 is an optical barrier in which many vertical strip-shaped apertures, namely slits 105 a , are formed. Near one surface of this parallax barrier 105 , there is arranged a display panel 106 .
- pixels for the right eye (hereinafter “right-eye pixels”) 123 and pixels for the left eye (hereinafter “left-eye pixels”) 124 are arranged in the direction orthogonal to the lengthwise direction of the slits 105 a .
- a light source 108 Near the other surface of the parallax barrier 105 , namely on the reverse side to the display panel 106 , there is arranged a light source 108 .
- Lights emitted from the light source 108 are partly intercepted by the parallax barrier 105 .
- a part of the lights having passed the slits 105 a without being intercepted by the parallax barrier 105 passes the right-eye pixels 123 to become luminous fluxes 181 or pass the left-eye pixels 124 to become luminous fluxes 182 .
- the position of the viewer to be able to perceive a three-dimensional image then is determined by the positional relationship between the parallax barrier 105 and the pixels.
- the right eye 141 of the viewer 104 it is necessary for the right eye 141 of the viewer 104 to be within the area where all the luminous fluxes 181 matching a plurality of right-eye pixels 123 pass and the viewer's left eye 142 to be within the area where all the luminous fluxes 182 pass.
- the viewer can perceive a three-dimensional image when the middle point 143 between the viewer's right eye 141 and left eye 142 is positioned within the rectangular three-dimensional visible area 107 shown in FIG. 12 .
- the line segment which passes the intersection point 107 a of diagonal lines in the three-dimensional visible area 107 is the longest, out of the line segments which extend in the arraying direction of the right-eye pixels 123 and the left-eye pixels 124 in the three-dimensional visible area 107 . For this reason, since the tolerance for lateral deviations of the viewer's position is at its maximum when the middle point 143 is located at the intersection point 107 a , this is the most preferable position of viewing.
- this distance between the intersection point 107 a and a display panel 106 is regarded as an optimal viewing distance OD, and the viewer is recommended to watch an image at this distance.
- a hypothetical plane whose distance from the display panel 106 constitutes the optimal viewing distance OD in the three-dimensional visible area 107 is referred to as the optimal viewing plane 107 b .
- the viewer is enabled to perceive the image displayed on the display panel 106 as a three-dimensional image.
- Table 1 in Nikkei Electronics , Jan. 6, 2003, No. 838, pp. 26-27 contains a cellular phone mounted with a 3D-compatible liquid crystal panel.
- the liquid crystal display panel constituting the three-dimensional image display device in this cellular phone measures 2.2 inches diagonally and has respectively 176 display dots horizontally and 220 display dots vertically.
- FIG. 13 shows a perspective view of a lenticular lens
- FIG. 14 is an optical model diagram illustrating a three-dimensional display method by the lenticular lens type.
- one face of a lenticular lens 121 is planar, and a plurality of convex semicircular cylindrical lenses 122 , extending in one direction, are formed in parallel to one another on the other face.
- a three-dimensional image display device of the lenticular lens type there are arranged the lenticular lens 121 , a display panel 106 and the light source 108 in the order away from the viewer, and pixels of the display panel 106 are positioned on the focal plane of the lenticular lens 121 .
- the pixels 123 for displaying the image for the right eye 141 and the pixels 124 for displaying that for the left eye 142 are alternately arranged.
- each group consisting of a pixel 123 and a pixel 124 adjoining each other matches one or another of the cylindrical lenses (convexes) 122 of the lenticular lens 121 .
- This arrangement enables lights emitted from the light source 108 and having passed the pixels to be divided by the cylindrical lenses 122 of the lenticular lens 121 into the directions toward the right and left eyes and enables the right and left eyes to perceive different images.
- the viewer is thereby enabled to perceive a three-dimensional image.
- the system by which the viewer is enabled to perceive a three-dimensional image by displaying an image for the right eye and another for the left eye is known as a two-viewpoint system because the formation of two points of view are involved.
- FIG. 15 is an optical model diagram of the three-dimensional image display device equipped with the conventional lenticular lens type
- FIG. 16 is an optical model diagram illustrating the three-dimensional visible area of this three-dimensional image display device.
- the distance between the vertex of the lenticular lens 121 and the pixels of the display panel 106 is represented by H, the refractive index of the lenticular lens 121 by n, the focal distance by f, and the array cycle of lens elements, namely the lens pitch, by L.
- Display pixels of the display panel 106 are arranged in a form of pairing one each of the left-eye pixel 124 and the right-eye pixel 123 .
- the pitch of these pixels is represented by P.
- the array pitch of display pixels of which each pair consists of one left-eye pixel 124 and one right-eye pixel 123 is 2P.
- One cylindrical lens 122 is arranged to match each pair of these one display pixels, consisting of one left-eye pixel 124 and one right-eye pixel 123 .
- the distance between the lenticular lens 121 and the viewer is supposed to be the optimal viewing distance OD
- the expanded projection width of pixels at this distance OD namely the width of each of the respective projected images of the left-eye pixels 124 and the right-eye pixels 123 on an imaginary plane at the distance OD from and parallel to the lens, is represented by e.
- the distance from the center of the cylindrical lens 122 positioned at the center of the lenticular lens 121 to the center of the cylindrical lens 122 positioned at an end of the lenticular lens 121 in the horizontal direction 112 is represented by WL, and the display panel 102 , and the distance between the center of the paired display pixels consisting of a left-eye pixel 124 and a right-eye pixel 123 and the center of the display pixels positioned at an end of the display panel 106 in the lens array direction 112 is represented by WP.
- the angle of incidence and the angle of emission of light at the cylindrical lens 122 positioned at the center of the lenticular lens 121 are represented by ⁇ and ⁇ , respectively, and the angle of incidence and the angle of emission of the cylindrical lens 122 at an end of the lenticular lens 121 in the lens array direction 112 are represented by ⁇ and ⁇ , respectively.
- the difference between the distances WL and WP is represented by C, and the number of pixels contained in the area of the distance WP, by 2m.
- the array cycle L of the cylindrical lenses 122 and the array cycle P of pixels are correlated, one is the basis of determining the other, but the lenticular lens is often designed to match the display panel, the array cycle P of pixels is treated as a constant.
- the refractive index n is determined by selecting a material for the lenticular lens 121 .
- the viewing distance OD between the lens and the viewer and the expanded projection width of pixels e at the viewing distance OD are set to desired values. These values are used in determining the distance H between the lens vertex and the pixels and the lens pitch L. According to the Snell laws of refraction and geometrical relationships, the following Formulas 1 through 6 hold.
- the area in which every light from the right-eye pixels 123 reaches is defined as the right-eye area 171
- the right eye 141 and the left eye 142 cannot be positioned in every desired position in the right-eye area 171 and the left-eye area 172 , respectively, but the visible range of the two eyes is limited to where the distance between the two eyes can be kept constant.
- the middle point between the right eye 141 and the left eye 142 is positioned in the three-dimensional visible area 107 , is three-dimensional viewing possible.
- the length along the horizontal direction 112 in the three-dimensional visible area 107 is the longest, and therefore the tolerance for the deviation of the viewer's position in the horizontal direction 112 is the greatest here. For this reason, the position where the distance from the three-dimensional image display device is equal to the optimal viewing distance OD is the ideal position of observation.
- the lenticular lens system changes the traveling direction of lights, and by its very principle is free from any decrease in the brightness of the display screen due to the presence of the lenticular lens. For this reason, it is considered to have good prospects for application to portable apparatuses, whose requirements for high luminance displaying and low power consumption are particularly stringent.
- a three-dimensional image display device developed by using the lenticular lens type is described in Reference 2 cited above.
- the liquid crystal display panel constituting this three-dimensional image display device measures seven inches in diagonal length, and has 800 display dots horizontally and 480 vertically.
- switch-over between three-dimensional and two-dimensional displays can be accomplished.
- an image display device capable of displaying different images toward a plurality of points of view
- a device simultaneously displaying a plurality of images is disclosed (see the Japanese Patent Application Laid-Open No. Hei 6-332354 (see FIG. 9 thereof)).
- the display simultaneously displays two-dimensional images, differing from one viewing direction to another, in the same conditions by utilizing the image portioning-out function of the lenticular lens, and thereby enables a plurality of different viewers to watch at the same time different two-dimensional images in respectively different directions with a single display device.
- FIG. 17 shows a perspective view of this simultaneous display of a plurality of images.
- the lenticular lens 121 and the display panel 106 are arranged in the direction away from the viewer 104 .
- pixels 125 for a first point of view to display an image for a first point of view and pixels 126 for a second point of view to display an image for a second point of view are alternately arranged.
- each group consisting of a pixel 125 and a pixel 126 adjoining each other matches one or another of the cylindrical lenses (convexes) 122 of the lenticular lens 121 .
- this arrangement enables lights transmitted through the pixels to be divided by the cylindrical lenses 122 of the lenticular lens 121 into different directions, the viewers can perceive different images in different positions.
- the use of this simultaneous display of a plurality of images can save an installation space, electric power charge and so forth compared with the installation of as many display devices as the viewers.
- liquid crystal display devices by virtue of their low power consumption and other advantages, find especially extensive use in smaller-size items including portable terminals.
- a liquid crystal display panel requires some external light source because it is a non-self-luminescent type, which displays an image by modulating external lights.
- a common transmissive liquid crystal display panel is equipped with illuminating means, known as a backlight unit, on the rear side of the liquid crystal display panel as seen from the viewer's side (see Akira Tanaka, “The latest trend of backlights for liquid crystals”, Monthly Display , June 1997, p. 75 (Reference 3)).
- FIG. 1 in Reference 3 illustrates the structure of a backlight unit for liquid crystal panel use.
- a backlight unit is configured of a light guiding plate for propagating lights from a light emitting source, the light emitting source known as an edge light (side light) arranged on a side of the light guiding plate, and an optical sheet arranged on the viewer's side of the light guiding plate. While the light emitted from the edge light propagates along the light guiding plate, part of the light is emitted toward the viewer, passes the transmissive liquid crystal display panel after being shaped by the optical sheet in terms of such optical characteristics as uniformity and angle distribution, and is incident on the viewer.
- FIG. 18 is an optical model diagram illustrating a conventional three-dimensional display device using a lenticular lens.
- a prism sheet or a lens sheet respectively consisting of many prisms or lenses, is frequently used as the optical sheet for the backlight unit.
- FIG. 18 on the surface of such a prism sheet or lens sheet, there are convexes or concaves deriving from the structure of the prisms or lenses.
- a portable terminal device is required to be thin to enhance their portability, and accordingly image display devices to be mounted on the portable terminal devices are also required to be thin.
- the present inventors tried a reduction in the distance between the pixels and the backlight unit, and found a problem that stripes emerge in the displayed images, and that the stripes cause a serious deterioration in display quality.
- exemplary feature of the present invention attempted in view of these problems, is to provide an image display device which is thin and having excellent display quality and a portable terminal device equipped with this image display device.
- a first exemplary aspect of the invention relates to an image display device including a display panel in which a plurality of display units including at least pixels for displaying an image for a first point of view and a second point of view are arrayed in a matrix shape; a lens for distributing lights transmitted through pixels for the first point of view and lights transmitted through pixels for the second point of view into mutually different directions; and an illuminating member which is arranged on the back of the display panel and on whose face toward the display panel a plurality of convexes or concaves are formed.
- the relationship between the spacing of convexes or that of concaves, and the array cycle of the lens is so set that the spacing of convexes be smaller than a prescribed value determined by the ratio between the distance between pixels and the convexes and the focal distance of the lens.
- the distance V defined by Formula 18 can reduce the influence of the directionality distribution of emitted lights attributable to the convexes.
- the invention can reduce the thickness of the image display device without sacrificing its display quality.
- the focal distance f may be shorter than the distance between the lens and the pixels. This would enable the focal positions of the lens to be set closer than the pixels toward the lens and accordingly a broader range of light rays to be used on the illuminating member. As a result, the distance between adjoining convexes may be extended, and therefore the image display device can be reduced in thickness without sacrificing its display quality because it can serve to reduce the influence of the directionality distribution of emitted lights attributable to convexes. Furthermore, as the focal position of the lens is off the pixel surface, the non-display areas between pixels can be vague, and accordingly the deterioration of displayed images attributable to the non-display areas can also be prevented.
- An image display device includes a display panel in which a plurality of display units including at least pixels for displaying an image for a first point of view and a second point of view are arrayed in a matrix shape; a lens for distributing lights transmitted through pixels for the first point of view and lights transmitted through pixels for the second point of view into mutually different directions; and an illuminating member which is arranged on the back of the display panel and on whose face toward the display panel a plurality of convexes or concaves are regularly formed, wherein the distance between adjoining convexes or concaves on the illuminating member is not longer than 0.6 mm.
- the invention which may use a transmissive liquid crystal panel of 0.15 mm in pixel pitch, the pitch most frequently used today in display panels for portable terminals, and of 0.3 mm in the array cycle of the lens, and in which display pixels include two types of pixels, can reduce the thickness of image display devices without sacrificing their display quality.
- the lens may be a fly-eye lens in which a plurality of convex lenses are arrayed in a matrix shape. As this enables lights transmitted through the lens to be distributed in four directions, different images can be displayed, distributed two-dimensionally.
- An image display device includes a display panel in which a plurality of display units including at least pixels for displaying an image for a first point of view and a second point of view are arrayed in a matrix shape; a lenticular lens provided with cylindrical lenses for distributing lights transmitted through pixels for the first point of view and lights transmitted through pixels for the second point of view into mutually different directions; and an illuminating member which is arranged on the back of the display panel and on whose face toward the display panel a plurality of convexes or concaves, inclined by an angle ⁇ to the lengthwise direction of the cylindrical lenses, are formed, wherein the following Formula 19 holds true regarding the distance V between adjoining convexes or concaves in the illuminating member, where S is the distance between the pixels and the convexes or concaves, f is the focal distance of the lens, L is the array cycle of the lens, and P v is the pixel pitch in the lengthwise direction of the cylindrical lenses:
- the invention by utilizing the one-dimensional lens action of the cylindrical lenses, deterioration in display quality attributable to the convexes or concaves of the illuminating member can be prevented.
- An image display device includes a display panel in which a plurality of display units including at least pixels for displaying an image for a first point of view and a second point of view are arrayed in a matrix shape; a lenticular lens provided with cylindrical lenses for distributing lights transmitted through pixels for the first point of view and lights transmitted through pixels for the second point of view into mutually different directions; and an illuminating member which is arranged on the back of the display panel and on whose face toward the display panel a plurality of convexes or concaves are formed, wherein the following Formula 20 holds true regarding the distance V v between adjoining convexes or concaves in the illuminating member in a direction inclined by an angle ⁇ to the lengthwise direction of the cylindrical lenses and the following Formula 21 holds true regarding the distance V between adjoining convexes or concaves in the illuminating member in a direction orthogonal to the direction inclined by the angle (to the lengthwise direction of the cylindrical lenses, where S is the
- the focal distance f may be shorter than the distance between the lenticular lens and the pixels. This would enable the focal positions of the lens to be set closer than the pixels toward the lens, and accordingly a broader range of light rays to be used on the illuminating member. As a result, the distance between adjoining convexes may be extended, and therefore the image display device can be reduced in thickness without sacrificing its display quality because it can serve to reduce the influence of the directionality distribution of emitted lights attributable to convexes or concaves. Furthermore, as the focal position of the lens is off the pixel surface, the influence of the non-display areas between pixels can be eased, and accordingly the deterioration of displayed images attributable to the non-display areas can also be prevented.
- the present invention enables image display devices to be reduced in thickness without sacrificing their display quality because it can serve to reduce the influence of the directionality distribution of emitted light rays, attributable to convexes or concaves formed in the illuminating member.
- FIG. 1 is an optical model diagram illustrating a three-dimensional image display device, which is a first exemplary embodiment of the present invention.
- FIG. 2 shows a perspective view of a portable terminal device mounted with the three-dimensional image display device of FIG. 1 .
- FIG. 3 is an optical model diagram illustrating a three-dimensional image display device, which is a second exemplary embodiment of the invention.
- FIG. 4 shows a perspective view of a fly-eye lens.
- FIG. 5 shows a partial perspective view of a three-dimensional image display device, which is a third exemplary embodiment of the invention.
- FIGS. 6( a ) and 6 ( b ) show schematic sectional views of the three-dimensional image display device, which is the third exemplary embodiment of the invention.
- FIG. 7 shows a partial perspective view of a three-dimensional image display device, which is a fourth exemplary embodiment of the invention.
- FIG. 8 shows a partial perspective view of a three-dimensional image display device, which is a fifth exemplary embodiment of the invention.
- FIG. 9 shows a partial perspective view of a three-dimensional image display device, which is a sixth exemplary embodiment of the invention.
- FIG. 10 shows a perspective view of a portable terminal device, which is a seventh exemplary embodiment of the invention.
- FIG. 11 is an optical model diagram illustrating the operation of the image display device embodying the invention in this mode.
- FIG. 12 is an optical model diagram illustrating a three-dimensional display method by the parallax barrier system.
- FIG. 13 shows a perspective view of a lenticular lens.
- FIG. 14 is an optical model diagram illustrating a three-dimensional display method by the lenticular lens type.
- FIG. 15 is an optical model diagram of a twin-lens three-dimensional image display device equipped with a conventional lenticular lens type.
- FIG. 16 is an optical model diagram illustrating the three-dimensional visible area of the twin-lens three-dimensional image display device shown in FIG. 15 .
- FIG. 17 shows a perspective view of simultaneous display of a plurality of images.
- FIG. 18 is an optical model diagram illustrating a conventional three-dimensional display device using a lenticular lens.
- the present inventors made earnest studies to reduce the thicknesses of image display devices, such as the three-dimensional image display device and the simultaneous display of a plurality of images described above, and to mount such displays on portable terminal devices. As a result, the following findings regarding the emergence of stripes in displayed images were obtained.
- a three-dimensional image display device if the purpose is merely to display a three-dimensional image, it will be sufficient to consider only an optical model on the pixels-to-the viewer side as shown in FIG. 16 .
- the distances from the display pixels (right-eye pixels 42 and left-eye pixels 41 ) to an optical sheet 51 provided on a backlight unit 5 , and the shape of convexes formed on the surface of the optical sheet 51 , as shown in FIG. 1 should be considered.
- FIG. 1 shows an optical model of the three-dimensional image display device embodying the invention in this mode.
- illustration of other constituent elements than pixels in the display panel is dispensed with in order to make the drawing easier to perceive.
- a lenticular lens 3 As shown in FIG. 1 , in the three-dimensional image display device 10 embodying the invention in this mode, a lenticular lens 3 , a display panel 2 and a backlight unit 5 are disposed in this order away from the viewer.
- the display panel 2 in this image display device 1 may be a transmissive liquid crystal panel for instance, and the display pixels on the display panel may include mutually adjoining right-eye pixels 42 and left-eye pixels 41 .
- Each group of display pixels are arrayed in the lengthwise direction of cylindrical lenses 3 a , and a lenticular lens 3 is so arranged that one or another of the cylindrical lenses 3 a matches each row of these arrayed display pixels.
- the optical sheet 51 on one face of which the convexes extending in one direction are formed is so arranged that the face with the convexes come to the display panel 2 side.
- the shape of these convexes formed on the optical sheet 51 is prismatic for instance, and the distance between adjacent convexes, namely the repeating pitch of the convexes, is represented by V.
- the display pixels are focused on, the focal distance f of the cylindrical lenses 3 a forming the lenticular lens 3 is equal to the distance between the vertexes of the lenses and the display pixels.
- the convexes of the optical sheet 51 are arrayed in one direction, and their lengthwise direction is identical with that of the cylindrical lenses 3 a .
- the convexes of the optical sheet 51 are arranged in the same direction as the cylindrical lenses 3 a .
- the array cycle of the cylindrical lenses 3 a being represented by L and the distance between the display pixels and the optical sheet 51 by S, the pitch V of the convexes on the optical sheet 51 satisfies the condition of the following Formula 24.
- the operation of the three-dimensional image display device 10 according to the first exemplary embodiment with note taken of one point among the display pixels of the display panel 2 .
- Lights emitted from the backlight unit 5 travel at many different angles. Therefore, light rays having passed a certain point among the display pixels are dispersed, and at the same time travel toward the lenticular lens 3 .
- the group of light rays coming incident on that cylindrical lens 3 a forms a triangle of which the base is the lens pitch L and the height is the focal distance f.
- the group of light rays emitted from the backlight unit 5 and directed toward the aforementioned one point among the display pixels also forms a triangle.
- the height of this triangle is the distance S from the display pixels to the optical sheet 51 . Since these two triangles are similar to each other, the relationship of the following Formula 25 holds, where X is the length of this latter triangle.
- the length X of the base of the triangle formed by the group of light rays emitted from the backlight unit 5 and being incident on the one point among the display pixels is not shorter than the pitch V of the prismatic convexes on the optical sheet 51 of the backlight unit 5 .
- the directionality distribution of the lights emitted from the backlight unit 5 also differs from one position of emission to another. For instance, where the length X of the base of the triangle is shorter than the pitch V of the convexes, the effect of the directionality distribution of emitted lights dependent on the position of convex is greater. However, since the length X of the base of the triangle is not shorter than the pitch V of the convexes in the three-dimensional image display device 10 of this exemplary embodiment, the effect can be eased even if the directionality distribution differs with the position of emission, because it is averaged over one cycle or more.
- a finite range X on the optical sheet 51 matches a certain one point on the viewing plane, and the finite range X on the optical sheet 51 varies matching the point on the viewing plane. It is note that with the luminance distribution of the optical sheet 51 in a certain finite range X, if the directionality distribution, i.e. the luminance distribution, of emitted lights differs with the position of the finite range X on the optical sheet, the brightness on the viewing plane will vary from position to position. Since this variation in brightness is observed superposed over the displayed image, picture quality seriously deteriorates.
- the luminance distribution in the finite range X is effective to uniformize the luminance distribution in the finite range X irrespective of its position on the optical sheet.
- the finite range X is set at or above the pitch V of the prismatic convexes on the optical sheet 51 , the luminance distribution in the finite range X can be uniformized irrespective of its position on the optical sheet 51 . This makes it possible to realize a thin image display device having excellent display quality.
- the advantages of the three-dimensional image display device 10 with reference to a two-viewpoint three-dimensional image display device using as the display panel 2 a transmissive liquid crystal display panel of which the glass substrate (not shown) is 0.7 mm thick and the pixel pitch is 0.15 mm, by way of example.
- the distance between the vertex of the lenticular lens 3 and the display pixels, and the focal distance f in this three-dimensional image display device are both equal to the thickness of the glass substrate (not shown), i.e. 0.7 mm.
- a polarizing plate which is an important item for a transmissive liquid crystal display panel, a multi-layered optical film (not shown) for enhancing the luminance, and a light-transmissive sticky film (not shown) for fixing the backlight unit 5 and the liquid crystal display panel to each other in this order.
- Their thicknesses are 0.7 mm for the glass substrate, 0.3 mm for the polarizing plate, 0.2 mm for the optical film, and 0.2 mm for the sticky film.
- the distance S from the display pixels to the optical sheet 51 i.e. the minimum thickness to allow the arrangement of these members is 1.4 mm.
- the convex pitch V on the optical sheet 51 at or below 0.6 mm, the effect of the directionality distribution of the convex on the optical sheet 51 can be eased, making it possible to realize an image display device having excellent display quality.
- the convex pitch V of the optical sheet 51 is greater than 0.6 mm, the distance from the display pixels to the optical sheet 51 should be extended to prevent deterioration in display quality. If, for instance, the convex pitch V of the optical sheet 51 is 1 mm, greater than X, as shown in FIG. 18 , the distance S from the display pixels to the optical sheet 51 should be 2 mm, resulting in a wasteful gap between the display pixels and the optical sheet 51 and a consequent increase in the thickness of the image display device.
- FIG. 2 shows a perspective view of a portable terminal device mounted with the three-dimensional image display device shown in FIG. 1 .
- this three-dimensional image display device 10 is mounted on a portable terminal device 9 , such as a cellular phone for example.
- an optical sheet on whose surface prismatic convexes extending in one direction are formed is used in the three-dimensional image display device 10 of this exemplary embodiment, the invention is not limited to this configuration.
- two optical sheets on whose surfaces prismatic convexes extending in one direction each are formed can be so disposed on the backlight unit 5 that the extending directions of the convexes orthogonally cross each other in a planar view.
- the pitch V of the optical sheets, whose convexes extend in the same direction as the arraying direction of the cylindrical lenses 3 a may be within a range defined by Formula 24 above.
- optical sheet on which prismatic convexes are arrayed in a matrix shape It is also possible to use an optical sheet on which prismatic convexes are arrayed in a matrix shape.
- an illuminating member including an optical sheet on which convexes are formed is arranged on a backlight unit, the use of the optical sheet on which convexes are disposed in a matrix shape gives the same effect as optical sheets on which convexes extend in one direction are used in two layers. As a result, the number of constituent members can be reduced with a corresponding saving in cost.
- the convexes are formed on the optical sheet 51 in the three-dimensional image display device 10 of this exemplary embodiment, the invention is not limited to this configuration.
- the same effect can be achieved by keeping the pitch of the convexes within the range defined by Formula 24 above. If the convexes have an in-plane distribution, then it is preferable for the minimum value of the pitch V to satisfy the requirement of Formula 24 above. Hence, the image display device could have a smaller thickness without sacrificing its display quality even if the distance V has an in-plane distribution.
- the shape of the convexes is not limited to being prismatic, but instead convexes could be provided on the surface of the backlight unit 5 , and the presence of the convexes results in a different directionality distribution of emitted lights in a microscopic region. Further a light dispersing member, more specifically an optical film or the like having a light scattering effect, could be formed over the convexes formed on the backlight unit 5 . This would reduce the influences of the convexes.
- a transmissive liquid crystal panel is supposed to be used as the display panel 2 in the three-dimensional image display device 10 of this exemplary embodiment, the invention is not limited to this, but can be applied to any display panel using the backlight unit 5 .
- the liquid crystal panel can be driven by either an active matrix system such as a thin film transistor (TFT) system or the thin film diode (TFD) system, or by a passive matrix system such as the super-twisted nematic liquid crystal (STN) system.
- TFT thin film transistor
- TFD thin film diode
- STN super-twisted nematic liquid crystal
- the image display device 1 in this exemplary embodiment can be applied not only to cellular phones or personal digital assistants (PDA) but also to various other portable terminals including game machines, digital still cameras, digital video cameras, note book computers, video players, DVD players, vending machines, monitors for medical use and ATMs (automated teller machine).
- PDA personal digital assistants
- ATMs automated teller machine
- FIG. 3 is an optical model diagram illustrating the three-dimensional image display device embodying the invention in this mode
- FIG. 4 shows a perspective view of a fly-eye lens.
- a three-dimensional image display device 20 of this exemplary embodiment is the same as the three-dimensional image display device 10 of the first exemplary embodiment described above except that a fly-eye lens 8 in which constituent lenses are formed in a matrix shape is used instead of the lenticular lens.
- the three-dimensional image display device 20 of this exemplary embodiment uses the fly-eye lens 8 , it is possible to distribute the lights of pixels transmitted through the lenses in four directions, up and down, and right and left. As a result, even if the arranging direction of the three-dimensional image display device 20 is turned, three-dimensional images can still be displayed.
- the convex pitch V in the optical sheet 51 is preferably within the range of Formula 24 above in the decreasing direction of the pitch.
- the convexes formed on the surface of the optical sheet 51 may be arrayed either in one direction or in a matrix shape.
- the pitch V of the optical sheet on the display panel 2 side is preferably within a range defined by Formula 24 above. That is, because the optical sheet on the display panel 2 side is shorter in distance to the display pixels, the condition for preventing the display quality from deterioration is more stringent.
- FIG. 5 shows a partial perspective view of the three-dimensional image display device, according to the third exemplary embodiment of the invention.
- FIG. 5 shows only part of the lenticular lens, part of the optical sheet and one pair of display pixels, but the illustration of all other constituent elements is dispensed with.
- the lengthwise direction of the cylindrical lenses 3 a forming the lenticular lens 3 is not identical with the direction in which prismatic convexes formed on the surface of the optical sheet 51 extend.
- the repeating pitch V of the convexes on the optical sheet 51 satisfies the condition of the following Formula 26, where ⁇ is the angle formed by the lengthwise direction of the cylindrical lenses 3 a with the extending direction of the prismatic convexes and P v is the pixel pitch of the cylindrical lenses 3 a in the lengthwise direction.
- FIGS. 6( a ) and 6 ( b ) show schematic sectional views of the backlight unit of the three-dimensional image display device or this exemplary embodiment, wherein FIG. 6( a ) is a sectional view along line A-A in FIG. 5 and FIG. 6( b ), one along line B-B.
- FIG. 6( a ) is a sectional view along line A-A in FIG. 5 and FIG. 6( b ), one along line B-B.
- the lenticular lens 3 and the optical sheet 51 are so arranged that the angle formed between the lengthwise direction of the cylindrical lenses 3 a and the extending direction of the prismatic convexes on the optical sheet 51 be ⁇
- the relative positions of the convex shape in FIGS. 6( a ) and 6 ( b ) differ by a value (P v ⁇ tan ⁇ ).
- the component in the arraying direction of the cylindrical lenses 3 a at the convex pitch V of the optical sheet 51 is a value (V/cos ⁇ ).
- the inclination angle ⁇ should be considered. Further, since the cylindrical lenses have no lens action in their consecutive direction (hereinafter referred to as the longitudinal direction), there is no separating action in the longitudinal direction. Thus, while there is significant separation in the arraying direction of the lenses (hereinafter referred to as the lateral direction), no separation occurs in the longitudinal direction.
- the optical sheet has convexes or concaves in the longitudinal direction, only the separating action of the lenses needs to be considered, but where they are arranged rotationally, the anisotropy of the lens action of the cylindrical lenses should also be considered.
- the absence of separating action by the cylindrical lenses in the longitudinal direction is positively utilized.
- the absence of separating action in the longitudinal direction means that superposition is allowed.
- the range of superposition surpasses the pixel pitch in the longitudinal direction, differences among pixels may occur, highly likely to result in observation of unevenness. Therefore, the range of superposition in the longitudinal direction is kept within the pixel pitch in the longitudinal direction.
- This value is to be made smaller than L ⁇ S/f as in the first exemplary embodiment of the invention.
- the effect of the optical sheet 51 can be attributed to the superposition of the convex arrangements shown in FIGS. 6( a ) and 6 ( b ). Therefore, the convexes on the optical sheet 51 become equivalent to what they are when they are arranged with their width expanded by a value (P v ⁇ tan ⁇ ). Further, since a component in the arraying direction of the cylindrical lenses 3 a at the convex pitch V of the optical sheet 51 is represented by the value (V/cos ⁇ ), the three-dimensional image display device of this exemplary embodiment provides the same effect as the three-dimensional image display device 10 of the first exemplary embodiment described above when the following Formula 27 holds.
- the three-dimensional image display device 30 of this exemplary embodiment is made thinner and superior in display quality by arranging the optical sheet 51 on which convexes extending in one direction are formed at an inclination relative to the lengthwise direction of the cylindrical lenses 3 a , and thereby utilizing the one-dimensional lens action of the cylindrical lenses to prevent deterioration in display quality attributable to the convexes of the optical sheet 51 .
- optical sheet 51 in the three-dimensional image display device of this exemplary embodiment is arranged rotated relative to the lengthwise direction of the cylindrical lenses 3 a , it is sufficient for the extending direction of the convexes on the optical sheet 51 not to be identical with the lengthwise direction of the cylindrical lenses 3 a.
- the optical sheet 51 can be so arranged that the extending direction of its convexes be parallel to a certain side of the three-dimensional image display device with the lenticular lens 3 being arranged rotated.
- the lenticular lens 3 can be arranged so that the lengthwise direction of the cylindrical lenses 3 a is parallel to one side of the display panel. This could relieve the user from the sense of awkwardness.
- a light dispersing member may as well be disposed between the display panel and the optical sheet 51 . This can ease the influence of the directionality distribution of emitted lights attributable to the convexes of the optical sheet 51 on displayed images. As a result, a thin image display device having excellent in display quality can be obtained.
- FIG. 7 shows a partial perspective view of the three-dimensional image display device of this exemplary embodiment of the invention.
- FIG. 7 shows only part of the lenticular lens, part of the optical sheet and one pair of display pixels, but the illustration of all other constituent elements is dispensed with.
- a three-dimensional image display device 40 of this exemplary embodiment has an optical sheet 52 on which convexes are formed in a matrix shape instead of the optical sheet 51 on which convexes extending in one direction are formed.
- other aspects of the configuration of the three-dimensional image display device 40 of this exemplary embodiment are similar to the three-dimensional image display device 30 of the third exemplary embodiment described above.
- the lengthwise direction of the cylindrical lenses 3 a is not identical with the direction in which prismatic convexes formed on the surface of the optical sheet 52 extend, and the pitch V v of the convexes inclined relative to the extending direction of the cylindrical lenses 3 a at an angle ⁇ satisfies the condition of the following Formula 28.
- P v in the following Formula 28 represents the pixel pitch in the lengthwise direction of the cylindrical lenses 3 a.
- This exemplary embodiment improves display quality by utilizing the anisotropy of the lens action of the cylindrical lenses.
- the use of the principle of superposition in the longitudinal direction necessitates definition of the pitch in the longitudinal direction.
- the pitch of convexes projected in the longitudinal direction is V v ⁇ cos ⁇ where V v is the convex pitch and ⁇ is the angle of rotation of the sheet. Since a plurality of convexes can be arranged per pixel if this value is not more than the pixel pitch P v in the longitudinal direction, the influence of the convexes can be reduced.
- the convex pitch in the lateral direction is prescribed and made extremely fine in the first and second exemplary embodiments, making it fine only in the lateral direction would invite an imbalance and make the manufacturing of the device more difficult, the effect in the longitudinal direction is also utilized.
- the three-dimensional image display device 40 of this exemplary embodiment is made thinner and superior in display quality by disposing an optical sheet 52 on which convexes extending in one direction are formed in a matrix shape at an inclination relative to the lengthwise direction of the cylindrical lenses 3 a and thereby utilizing the one-dimensional lens action of the cylindrical lenses to prevent deterioration in display quality attributable to the convexes.
- optical sheet 52 on which convexes are formed in a matrix shape gives the same effect as two optical sheets on which convexes extend in one direction are used. As a result, the number of constituent members can be reduced with a corresponding saving in manufacturing cost.
- FIG. 8 is an optical model diagram illustrating the three-dimensional image display device of this exemplary embodiment.
- the illustration of other constituent elements than pixels on the display panel 2 is dispensed with.
- the foci of the cylindrical lenses 3 a forming the lenticular lens 3 are set closer than the display pixels toward the lenticular lens 3 with the result that the focal distance f is shorter than the distance H between the vertexes of the lenses and the pixels.
- Formula 29 holds.
- the foci of the lenses 3 a are set closer than the display pixels toward the lenticular lens 3 , light rays in a broader range on the backlight unit 5 may be used.
- FIG. 9 is an optical model diagram illustrating the three-dimensional image display device of this exemplary embodiment.
- the foci of the lenses forming the fly-eye lens 8 are set closer than the display pixels toward the fly-eye lens 8 with the result that the focal distance f is shorter than the distance H between the vertexes of the lenses and the pixels. Accordingly the following Formula 30 holds.
- the other aspects of the configuration of a three-dimensional image display device 60 of this exemplary embodiment are the same as those of the three-dimensional image display device 20 of the second exemplary embodiment described above.
- the focal positions of the lenses are set closer than the display pixels toward the fly-eye lens 8 , light rays in a broader range on the backlight unit 5 can be used in addition to the effects of the three-dimensional image display device 20 of the second exemplary embodiment described above.
- an optical sheet longer in the convex pitch may be used, and accordingly the influence of the directionality distribution of emitted lights attributable to the convexes can be eased.
- the focal positions of the lenses are off the pixel surface, the influence of the non-display areas between pixels can be eased, and accordingly the deterioration of displayed images attributable to the non-display areas can also be prevented.
- the three-dimensional image display devices of the first through sixth exemplary embodiments may as well be two-dimensional image display devices.
- Such an image display device where it is mounted on portable terminal device for instance, the user can watch images for a plurality of points of view by merely varying the angle of the portable terminal device.
- each image can be viewed by a simple method of changing the angle of viewing, resulting in a substantial improvement in convenience.
- images for a plurality of points of view are arrayed in the longitudinal direction, the viewer can watch the image for each point of view with two eyes all the time, resulting in improved perceptibility of the image for each point of view.
- a liquid crystal display panel may be used as the display panel.
- FIG. 10 shows a perspective view of the portable terminal device of this exemplary embodiment
- FIG. 11 is an optical model diagram illustrating the operation of an image display device mounted on the portable terminal device embodying the invention in this mode.
- a portable terminal device 9 of this exemplary embodiment is a cellular phone with an image display device 70 built into it.
- the arraying direction of the cylindrical lenses 3 a forming the lenticular lens 3 is a longitudinal direction 11 , i.e. the vertical direction of images
- the lengthwise direction of the cylindrical lenses 3 a is a lateral direction 12 , i.e. the horizontal direction of images.
- the arraying direction of the first-viewpoint pixels 43 and the second-viewpoint pixels 44 in one pair of display pixels of the display panel is a longitudinal direction 11 , the same as the arraying direction of the cylindrical lenses 3 a . Incidentally, though only four of the cylindrical lenses 3 a are shown in FIG.
- the backlight unit 5 emits lights, which are incident on the display panel 2 .
- the first-viewpoint pixels 43 of the display panel 2 display a first-viewpoint image
- the second-viewpoint pixels 44 display a second-viewpoint image.
- the lights being incident on the first-viewpoint pixels 43 and the second-viewpoint pixels 44 of the display panel 2 are transmitted by these pixels, and travel toward the lenticular lens 3 .
- These lights are refracted by the cylindrical lenses 3 a of the lenticular lens 3 , and are emitted toward areas E 1 and E 2 .
- the areas and E 1 and E 2 are arrayed in the longitudinal direction 11 . If then the viewer positions his eyes on the area E 1 , he can view the first-viewpoint image or, if he positions his eyes on the area E 2 , he can view the second-viewpoint image.
- the portable terminal device 9 of this exemplary embodiment has an advantage that the viewer can position both his eyes on the area E 1 or E 2 by merely varying the angle of the portable terminal device 9 , and thereby watch the first-viewpoint image or the second-viewpoint image. Especially where the first-viewpoint image and the second-viewpoint image are correlated, he can view each image by a simple method of changing the angle of viewing, resulting in a substantial improvement in convenience.
Abstract
An image display device includes a display panel, a lens, a backlight, and a light dispersing member. The display panel includes a plurality of display units including at least pixels for displaying an image for a first point of view and a second point of view, arrayed in a matrix shape. The lens distributes lights transmitted through pixels for the first and second points of view into mutually different directions. The backlight has a plurality of convexes or concaves which refract lights. The light dispersing member is disposed between the display panel and backlight.
Description
- The present application is a Continuing Application of U.S. patent application Ser. No. 11/168,932 filed on Jun. 29, 2005.
- 1. Field of the Invention
- The present invention relates to an image display device capable of displaying an image toward a plurality of points of view and a portable terminal device mounted with this image display device.
- 2. Description of the Related Art
- Attempts have been made to develop an image display device capable of displaying different images toward a plurality of points of view. One example is a three-dimensional image display device. The three-dimensional image display device displays parallax images for the right eye and left eye, and a viewer looking with both eyes at the images differentiated between right and left can perceive a three-dimensional image.
- To realize this function concretely, many three-dimensional image display systems have been studied. Three-dimensional image display systems can be broadly classified into two types, one using glasses and the other using no glasses. The former can be further subdivided into the anaglyph type utilizing differences in color and the polarization glass type. But both of them have the essential problem that the viewer must use glasses. For this reason, the latter, using no glasses, has become more popular, and this can be sub-classified into the parallax barrier type and the lenticular lens type.
- First will be described the parallax barrier type. The parallax barrier type was conceived by Berthier in 1896 and verified by Ives in 1903.
FIG. 12 is an optical model diagram illustrating a three-dimensional display method by the parallax barrier system. As shown inFIG. 12 , aparallax barrier 105 is an optical barrier in which many vertical strip-shaped apertures, namelyslits 105 a, are formed. Near one surface of thisparallax barrier 105, there is arranged adisplay panel 106. In thedisplay panel 106, pixels for the right eye (hereinafter “right-eye pixels”) 123 and pixels for the left eye (hereinafter “left-eye pixels”) 124 are arranged in the direction orthogonal to the lengthwise direction of theslits 105 a. Near the other surface of theparallax barrier 105, namely on the reverse side to thedisplay panel 106, there is arranged alight source 108. - Lights emitted from the
light source 108 are partly intercepted by theparallax barrier 105. On the other hand, a part of the lights having passed theslits 105 a without being intercepted by theparallax barrier 105 passes the right-eye pixels 123 to becomeluminous fluxes 181 or pass the left-eye pixels 124 to becomeluminous fluxes 182. The position of the viewer to be able to perceive a three-dimensional image then is determined by the positional relationship between theparallax barrier 105 and the pixels. Thus, it is necessary for theright eye 141 of theviewer 104 to be within the area where all theluminous fluxes 181 matching a plurality of right-eye pixels 123 pass and the viewer'sleft eye 142 to be within the area where all theluminous fluxes 182 pass. The viewer can perceive a three-dimensional image when themiddle point 143 between the viewer'sright eye 141 andleft eye 142 is positioned within the rectangular three-dimensionalvisible area 107 shown inFIG. 12 . - The line segment which passes the
intersection point 107 a of diagonal lines in the three-dimensionalvisible area 107 is the longest, out of the line segments which extend in the arraying direction of the right-eye pixels 123 and the left-eye pixels 124 in the three-dimensionalvisible area 107. For this reason, since the tolerance for lateral deviations of the viewer's position is at its maximum when themiddle point 143 is located at theintersection point 107 a, this is the most preferable position of viewing. - Therefore, by this three-dimensional image display method, this distance between the
intersection point 107 a and adisplay panel 106 is regarded as an optimal viewing distance OD, and the viewer is recommended to watch an image at this distance. A hypothetical plane whose distance from thedisplay panel 106 constitutes the optimal viewing distance OD in the three-dimensionalvisible area 107 is referred to as theoptimal viewing plane 107 b. This causes lights from the right-eye pixels 123 and the left-eye pixels 124 to reach the viewer'sright eye 141 andleft eye 142, respectively. As a result, the viewer is enabled to perceive the image displayed on thedisplay panel 106 as a three-dimensional image. - For instance, Table 1 in Nikkei Electronics, Jan. 6, 2003, No. 838, pp. 26-27 (Reference 2) contains a cellular phone mounted with a 3D-compatible liquid crystal panel. The liquid crystal display panel constituting the three-dimensional image display device in this cellular phone measures 2.2 inches diagonally and has respectively 176 display dots horizontally and 220 display dots vertically. There is further provided a liquid crystal panel for the switching purpose to turn on and off the effect of a parallax barrier, permitting change-over between three-dimensional and two-dimensional displays.
- Next will be described the lenticular lens type. The lenticular lens type was invented in or around 1910 by Ives and others as described in, for instance, Chihiro Masuda, Three-Dimensional Display, Sangyo Tosho Kabushiki Kaisha, p. 1 (Reference 1).
FIG. 13 shows a perspective view of a lenticular lens, andFIG. 14 is an optical model diagram illustrating a three-dimensional display method by the lenticular lens type. As shown inFIG. 13 , one face of alenticular lens 121 is planar, and a plurality of convex semicircularcylindrical lenses 122, extending in one direction, are formed in parallel to one another on the other face. - Then, as shown in
FIG. 14 , in a three-dimensional image display device of the lenticular lens type, there are arranged thelenticular lens 121, adisplay panel 106 and thelight source 108 in the order away from the viewer, and pixels of thedisplay panel 106 are positioned on the focal plane of thelenticular lens 121. On thedisplay panel 106, thepixels 123 for displaying the image for theright eye 141 and thepixels 124 for displaying that for theleft eye 142 are alternately arranged. In this arrangement each group consisting of apixel 123 and apixel 124 adjoining each other matches one or another of the cylindrical lenses (convexes) 122 of thelenticular lens 121. This arrangement enables lights emitted from thelight source 108 and having passed the pixels to be divided by thecylindrical lenses 122 of thelenticular lens 121 into the directions toward the right and left eyes and enables the right and left eyes to perceive different images. The viewer is thereby enabled to perceive a three-dimensional image. The system by which the viewer is enabled to perceive a three-dimensional image by displaying an image for the right eye and another for the left eye is known as a two-viewpoint system because the formation of two points of view are involved. - Next will be described in detail the size of each part of the three-dimensional image display device equipped with a conventional lenticular lens and a display panel.
FIG. 15 is an optical model diagram of the three-dimensional image display device equipped with the conventional lenticular lens type, andFIG. 16 is an optical model diagram illustrating the three-dimensional visible area of this three-dimensional image display device. - As shown in
FIG. 15 , the distance between the vertex of thelenticular lens 121 and the pixels of thedisplay panel 106 is represented by H, the refractive index of thelenticular lens 121 by n, the focal distance by f, and the array cycle of lens elements, namely the lens pitch, by L. Display pixels of thedisplay panel 106 are arranged in a form of pairing one each of the left-eye pixel 124 and the right-eye pixel 123. The pitch of these pixels is represented by P. - Therefore, the array pitch of display pixels, of which each pair consists of one left-
eye pixel 124 and one right-eye pixel 123 is 2P. Onecylindrical lens 122 is arranged to match each pair of these one display pixels, consisting of one left-eye pixel 124 and one right-eye pixel 123. - The distance between the
lenticular lens 121 and the viewer is supposed to be the optimal viewing distance OD, the expanded projection width of pixels at this distance OD, namely the width of each of the respective projected images of the left-eye pixels 124 and the right-eye pixels 123 on an imaginary plane at the distance OD from and parallel to the lens, is represented by e. - Further, the distance from the center of the
cylindrical lens 122 positioned at the center of thelenticular lens 121 to the center of thecylindrical lens 122 positioned at an end of thelenticular lens 121 in thehorizontal direction 112 is represented by WL, and the display panel 102, and the distance between the center of the paired display pixels consisting of a left-eye pixel 124 and a right-eye pixel 123 and the center of the display pixels positioned at an end of thedisplay panel 106 in thelens array direction 112 is represented by WP. Then, the angle of incidence and the angle of emission of light at thecylindrical lens 122 positioned at the center of thelenticular lens 121 are represented by α and β, respectively, and the angle of incidence and the angle of emission of thecylindrical lens 122 at an end of thelenticular lens 121 in thelens array direction 112 are represented by γ and δ, respectively. Further the difference between the distances WL and WP is represented by C, and the number of pixels contained in the area of the distance WP, by 2m. - Since the array cycle L of the
cylindrical lenses 122 and the array cycle P of pixels are correlated, one is the basis of determining the other, but the lenticular lens is often designed to match the display panel, the array cycle P of pixels is treated as a constant. The refractive index n is determined by selecting a material for thelenticular lens 121. Unlike these factors, the viewing distance OD between the lens and the viewer and the expanded projection width of pixels e at the viewing distance OD are set to desired values. These values are used in determining the distance H between the lens vertex and the pixels and the lens pitch L. According to the Snell laws of refraction and geometrical relationships, the followingFormulas 1 through 6 hold. -
n×sin α=sin β (Formula 1) -
OD×tan β=e (Formula 2) -
H×tan α=P (Formula 3) -
n×sin γ=sin δ (Formula 4) -
H×tan γ=C (Formula 5) -
OD×tan δ=WL (Formula 6) - The following Formulas 7 through 9 also hold.
-
W P −W L =C (Formula 7) -
W P=2×m×P (Formula 8) -
W L =m×L (Formula 9) - From
Formulas 1 through 3 above derive the followingFormulas 10 through 12, respectively. -
β=arctan(e/OD) (Formula 10) -
α=arcsin(1/n×sin β) (Formula 11) -
H=P/tan α (Formula 12) - From Formula 6 and
Formula 9 above derives the following Formula 13. -
δ=arctan(mL/OD) (Formula 13) - Further from Formula 7 and
Formula 8 above derives the following Formula 14. -
C=2×m×P−m×L (Formula 14) - Further from
Formula 5 above derives the following Formula 15. -
γ=arctan(C/H) (Formula 15) - Incidentally, as the distance H between the vertex of the lenticular lens and the pixels is usually equalized to the focal distance f of the lenticular lens, the following Formula 16 holds, and the radius of curvature of the lens, represented here by r, is figured out by the following Formula 17.
-
f=H (Formula 16) -
r=H×(n−1)/n (Formula 17) - As shown in
FIG. 16 , the area in which every light from the right-eye pixels 123 reaches is defined as the right-eye area 171, and the area in which every light from the left-eye pixels 124 reaches, as the left-eye area 172. If the viewer positions hisright eye 141 in the right-eye area 171 and hisleft eye 142 in the left-eye area 172, then he can perceive a three-dimensional image. - However, as the distance between the viewer's two eyes is fixed, the
right eye 141 and theleft eye 142 cannot be positioned in every desired position in the right-eye area 171 and the left-eye area 172, respectively, but the visible range of the two eyes is limited to where the distance between the two eyes can be kept constant. Thus, only when the middle point between theright eye 141 and theleft eye 142 is positioned in the three-dimensionalvisible area 107, is three-dimensional viewing possible. In the position where the distance from the three-dimensional image display device is equal to the optimal viewing distance OD, the length along thehorizontal direction 112 in the three-dimensionalvisible area 107 is the longest, and therefore the tolerance for the deviation of the viewer's position in thehorizontal direction 112 is the greatest here. For this reason, the position where the distance from the three-dimensional image display device is equal to the optimal viewing distance OD is the ideal position of observation. - While the parallax barrier system previously described “conceals” unnecessary lights with the barrier, the lenticular lens system changes the traveling direction of lights, and by its very principle is free from any decrease in the brightness of the display screen due to the presence of the lenticular lens. For this reason, it is considered to have good prospects for application to portable apparatuses, whose requirements for high luminance displaying and low power consumption are particularly stringent.
- A three-dimensional image display device developed by using the lenticular lens type is described in
Reference 2 cited above. The liquid crystal display panel constituting this three-dimensional image display device measures seven inches in diagonal length, and has 800 display dots horizontally and 480 vertically. By varying the distance between the lenticular lens and the liquid crystal display panel by 0.6 mm, switch-over between three-dimensional and two-dimensional displays can be accomplished. - As another example of an image display device capable of displaying different images toward a plurality of points of view, a device simultaneously displaying a plurality of images is disclosed (see the Japanese Patent Application Laid-Open No. Hei 6-332354 (see
FIG. 9 thereof)). The display simultaneously displays two-dimensional images, differing from one viewing direction to another, in the same conditions by utilizing the image portioning-out function of the lenticular lens, and thereby enables a plurality of different viewers to watch at the same time different two-dimensional images in respectively different directions with a single display device. -
FIG. 17 shows a perspective view of this simultaneous display of a plurality of images. As shown inFIG. 17 , in this simultaneous display of a plurality of images, thelenticular lens 121 and thedisplay panel 106 are arranged in the direction away from theviewer 104. On thedisplay panel 106,pixels 125 for a first point of view to display an image for a first point of view andpixels 126 for a second point of view to display an image for a second point of view are alternately arranged. In this arrangement each group consisting of apixel 125 and apixel 126 adjoining each other matches one or another of the cylindrical lenses (convexes) 122 of thelenticular lens 121. As this arrangement enables lights transmitted through the pixels to be divided by thecylindrical lenses 122 of thelenticular lens 121 into different directions, the viewers can perceive different images in different positions. The use of this simultaneous display of a plurality of images can save an installation space, electric power charge and so forth compared with the installation of as many display devices as the viewers. - On the other hand, liquid crystal display devices, by virtue of their low power consumption and other advantages, find especially extensive use in smaller-size items including portable terminals. A liquid crystal display panel requires some external light source because it is a non-self-luminescent type, which displays an image by modulating external lights. In a common transmissive liquid crystal display panel is equipped with illuminating means, known as a backlight unit, on the rear side of the liquid crystal display panel as seen from the viewer's side (see Akira Tanaka, “The latest trend of backlights for liquid crystals”, Monthly Display, June 1997, p. 75 (Reference 3)).
- FIG. 1 in
Reference 3 illustrates the structure of a backlight unit for liquid crystal panel use. Usually, a backlight unit is configured of a light guiding plate for propagating lights from a light emitting source, the light emitting source known as an edge light (side light) arranged on a side of the light guiding plate, and an optical sheet arranged on the viewer's side of the light guiding plate. While the light emitted from the edge light propagates along the light guiding plate, part of the light is emitted toward the viewer, passes the transmissive liquid crystal display panel after being shaped by the optical sheet in terms of such optical characteristics as uniformity and angle distribution, and is incident on the viewer. -
FIG. 18 is an optical model diagram illustrating a conventional three-dimensional display device using a lenticular lens. As described inReference 3, a prism sheet or a lens sheet, respectively consisting of many prisms or lenses, is frequently used as the optical sheet for the backlight unit. As shown inFIG. 18 , on the surface of such a prism sheet or lens sheet, there are convexes or concaves deriving from the structure of the prisms or lenses. - However, the examples of the prior art described above involve problems. A portable terminal device is required to be thin to enhance their portability, and accordingly image display devices to be mounted on the portable terminal devices are also required to be thin.
- In view of the foregoing and other exemplary problem, the present inventors tried a reduction in the distance between the pixels and the backlight unit, and found a problem that stripes emerge in the displayed images, and that the stripes cause a serious deterioration in display quality.
- Accordingly exemplary feature of the present invention, attempted in view of these problems, is to provide an image display device which is thin and having excellent display quality and a portable terminal device equipped with this image display device.
- A first exemplary aspect of the invention relates to an image display device including a display panel in which a plurality of display units including at least pixels for displaying an image for a first point of view and a second point of view are arrayed in a matrix shape; a lens for distributing lights transmitted through pixels for the first point of view and lights transmitted through pixels for the second point of view into mutually different directions; and an illuminating member which is arranged on the back of the display panel and on whose face toward the display panel a plurality of convexes or concaves are formed.
- Herein the following Formula 18 holds true regarding the distance V between adjoining convexes or concaves in the illuminating member, where S is the distance between the pixels and the convexes or concaves, f is the focal distance of the lens, and L is the array cycle of the lens:
-
V≦L×S/f (Formula 18) - Thus, the relationship between the spacing of convexes or that of concaves, and the array cycle of the lens is so set that the spacing of convexes be smaller than a prescribed value determined by the ratio between the distance between pixels and the convexes and the focal distance of the lens. Whereas lights emitted from the illuminating member differ in directionality distribution with the inclination angle of the convexes, the distance V defined by Formula 18 can reduce the influence of the directionality distribution of emitted lights attributable to the convexes. Thus, by satisfying the condition of Formula 18, the number of convexes projected by one lens on the viewing plane can be made one or more, and accordingly the influence of distribution can be evened out. In this way, the invention can reduce the thickness of the image display device without sacrificing its display quality.
- The focal distance f may be shorter than the distance between the lens and the pixels. This would enable the focal positions of the lens to be set closer than the pixels toward the lens and accordingly a broader range of light rays to be used on the illuminating member. As a result, the distance between adjoining convexes may be extended, and therefore the image display device can be reduced in thickness without sacrificing its display quality because it can serve to reduce the influence of the directionality distribution of emitted lights attributable to convexes. Furthermore, as the focal position of the lens is off the pixel surface, the non-display areas between pixels can be vague, and accordingly the deterioration of displayed images attributable to the non-display areas can also be prevented.
- Where concaves are used instead of convexes to pick up emitted lights, the convexes in the foregoing description can be read as “concaves” to explain the same effects.
- An image display device according to a second exemplary aspect of the invention includes a display panel in which a plurality of display units including at least pixels for displaying an image for a first point of view and a second point of view are arrayed in a matrix shape; a lens for distributing lights transmitted through pixels for the first point of view and lights transmitted through pixels for the second point of view into mutually different directions; and an illuminating member which is arranged on the back of the display panel and on whose face toward the display panel a plurality of convexes or concaves are regularly formed, wherein the distance between adjoining convexes or concaves on the illuminating member is not longer than 0.6 mm.
- The invention, which may use a transmissive liquid crystal panel of 0.15 mm in pixel pitch, the pitch most frequently used today in display panels for portable terminals, and of 0.3 mm in the array cycle of the lens, and in which display pixels include two types of pixels, can reduce the thickness of image display devices without sacrificing their display quality.
- The lens may be a fly-eye lens in which a plurality of convex lenses are arrayed in a matrix shape. As this enables lights transmitted through the lens to be distributed in four directions, different images can be displayed, distributed two-dimensionally.
- An image display device according to a third exemplary aspect of the invention includes a display panel in which a plurality of display units including at least pixels for displaying an image for a first point of view and a second point of view are arrayed in a matrix shape; a lenticular lens provided with cylindrical lenses for distributing lights transmitted through pixels for the first point of view and lights transmitted through pixels for the second point of view into mutually different directions; and an illuminating member which is arranged on the back of the display panel and on whose face toward the display panel a plurality of convexes or concaves, inclined by an angle θ to the lengthwise direction of the cylindrical lenses, are formed, wherein the following Formula 19 holds true regarding the distance V between adjoining convexes or concaves in the illuminating member, where S is the distance between the pixels and the convexes or concaves, f is the focal distance of the lens, L is the array cycle of the lens, and Pv is the pixel pitch in the lengthwise direction of the cylindrical lenses:
-
V≦L×S×(cos θ)/f+Pv×(sin θ) (Formula 19) - According to the invention, by utilizing the one-dimensional lens action of the cylindrical lenses, deterioration in display quality attributable to the convexes or concaves of the illuminating member can be prevented.
- An image display device according to a fourth exemplary aspect of the invention includes a display panel in which a plurality of display units including at least pixels for displaying an image for a first point of view and a second point of view are arrayed in a matrix shape; a lenticular lens provided with cylindrical lenses for distributing lights transmitted through pixels for the first point of view and lights transmitted through pixels for the second point of view into mutually different directions; and an illuminating member which is arranged on the back of the display panel and on whose face toward the display panel a plurality of convexes or concaves are formed, wherein the following
Formula 20 holds true regarding the distance Vv between adjoining convexes or concaves in the illuminating member in a direction inclined by an angle θ to the lengthwise direction of the cylindrical lenses and the following Formula 21 holds true regarding the distance V between adjoining convexes or concaves in the illuminating member in a direction orthogonal to the direction inclined by the angle (to the lengthwise direction of the cylindrical lenses, where S is the distance between the pixels and the convexes or concaves, f is the focal distance of the lens, L is the array cycle of the lens, and Pv is the pixel pitch in the lengthwise direction of the cylindrical lenses: -
V v ≦P v/cos θ (Formula 20) -
V≦L×S×(cos θ)/f+P v×(sin θ) (Formula 21) - The focal distance f may be shorter than the distance between the lenticular lens and the pixels. This would enable the focal positions of the lens to be set closer than the pixels toward the lens, and accordingly a broader range of light rays to be used on the illuminating member. As a result, the distance between adjoining convexes may be extended, and therefore the image display device can be reduced in thickness without sacrificing its display quality because it can serve to reduce the influence of the directionality distribution of emitted lights attributable to convexes or concaves. Furthermore, as the focal position of the lens is off the pixel surface, the influence of the non-display areas between pixels can be eased, and accordingly the deterioration of displayed images attributable to the non-display areas can also be prevented.
- The present invention enables image display devices to be reduced in thickness without sacrificing their display quality because it can serve to reduce the influence of the directionality distribution of emitted light rays, attributable to convexes or concaves formed in the illuminating member.
-
FIG. 1 is an optical model diagram illustrating a three-dimensional image display device, which is a first exemplary embodiment of the present invention. -
FIG. 2 shows a perspective view of a portable terminal device mounted with the three-dimensional image display device ofFIG. 1 . -
FIG. 3 is an optical model diagram illustrating a three-dimensional image display device, which is a second exemplary embodiment of the invention. -
FIG. 4 shows a perspective view of a fly-eye lens. -
FIG. 5 shows a partial perspective view of a three-dimensional image display device, which is a third exemplary embodiment of the invention. -
FIGS. 6( a) and 6(b) show schematic sectional views of the three-dimensional image display device, which is the third exemplary embodiment of the invention. -
FIG. 7 shows a partial perspective view of a three-dimensional image display device, which is a fourth exemplary embodiment of the invention. -
FIG. 8 shows a partial perspective view of a three-dimensional image display device, which is a fifth exemplary embodiment of the invention. -
FIG. 9 shows a partial perspective view of a three-dimensional image display device, which is a sixth exemplary embodiment of the invention. -
FIG. 10 shows a perspective view of a portable terminal device, which is a seventh exemplary embodiment of the invention. -
FIG. 11 is an optical model diagram illustrating the operation of the image display device embodying the invention in this mode. -
FIG. 12 is an optical model diagram illustrating a three-dimensional display method by the parallax barrier system. -
FIG. 13 shows a perspective view of a lenticular lens. -
FIG. 14 is an optical model diagram illustrating a three-dimensional display method by the lenticular lens type. -
FIG. 15 is an optical model diagram of a twin-lens three-dimensional image display device equipped with a conventional lenticular lens type. -
FIG. 16 is an optical model diagram illustrating the three-dimensional visible area of the twin-lens three-dimensional image display device shown inFIG. 15 . -
FIG. 17 shows a perspective view of simultaneous display of a plurality of images. -
FIG. 18 is an optical model diagram illustrating a conventional three-dimensional display device using a lenticular lens. - With a view to solving the problems noted above, the present inventors made earnest studies to reduce the thicknesses of image display devices, such as the three-dimensional image display device and the simultaneous display of a plurality of images described above, and to mount such displays on portable terminal devices. As a result, the following findings regarding the emergence of stripes in displayed images were obtained. In a three-dimensional image display device, if the purpose is merely to display a three-dimensional image, it will be sufficient to consider only an optical model on the pixels-to-the viewer side as shown in
FIG. 16 . However, if the device is to be reduced in thickness and enhanced in picture quality, the distances from the display pixels (right-eye pixels 42 and left-eye pixels 41) to anoptical sheet 51 provided on abacklight unit 5, and the shape of convexes formed on the surface of theoptical sheet 51, as shown inFIG. 1 should be considered. - Image display devices, which are exemplary embodiments of the present invention, will be described below in specific terms with reference to the accompanying drawings. First will be described a three-dimensional image display device, which is a first exemplary embodiment of the invention.
FIG. 1 shows an optical model of the three-dimensional image display device embodying the invention in this mode. InFIG. 1 , illustration of other constituent elements than pixels in the display panel is dispensed with in order to make the drawing easier to perceive. - As shown in
FIG. 1 , in the three-dimensionalimage display device 10 embodying the invention in this mode, alenticular lens 3, adisplay panel 2 and abacklight unit 5 are disposed in this order away from the viewer. Thedisplay panel 2 in thisimage display device 1 may be a transmissive liquid crystal panel for instance, and the display pixels on the display panel may include mutually adjoining right-eye pixels 42 and left-eye pixels 41. Each group of display pixels are arrayed in the lengthwise direction ofcylindrical lenses 3 a, and alenticular lens 3 is so arranged that one or another of thecylindrical lenses 3 a matches each row of these arrayed display pixels. - On a face of the
backlight unit 5 of thedisplay panel 2 side, theoptical sheet 51 on one face of which the convexes extending in one direction are formed, is so arranged that the face with the convexes come to thedisplay panel 2 side. The shape of these convexes formed on theoptical sheet 51 is prismatic for instance, and the distance between adjacent convexes, namely the repeating pitch of the convexes, is represented by V. In theimage display device 10 of this exemplary embodiment, the display pixels are focused on, the focal distance f of thecylindrical lenses 3 a forming thelenticular lens 3 is equal to the distance between the vertexes of the lenses and the display pixels. - Further, the convexes of the
optical sheet 51 are arrayed in one direction, and their lengthwise direction is identical with that of thecylindrical lenses 3 a. Thus, the convexes of theoptical sheet 51 are arranged in the same direction as thecylindrical lenses 3 a. The array cycle of thecylindrical lenses 3 a being represented by L and the distance between the display pixels and theoptical sheet 51 by S, the pitch V of the convexes on theoptical sheet 51 satisfies the condition of the following Formula 24. -
V≦L×S/f (Formula 24) - Next will be described the operation of the three-dimensional
image display device 10 according to the first exemplary embodiment with note taken of one point among the display pixels of thedisplay panel 2. Lights emitted from thebacklight unit 5 travel at many different angles. Therefore, light rays having passed a certain point among the display pixels are dispersed, and at the same time travel toward thelenticular lens 3. To take note of one of thecylindrical lenses 3 a forming thelenticular lens 3, the group of light rays coming incident on thatcylindrical lens 3 a forms a triangle of which the base is the lens pitch L and the height is the focal distance f. On the other hand, the group of light rays emitted from thebacklight unit 5 and directed toward the aforementioned one point among the display pixels also forms a triangle. The height of this triangle is the distance S from the display pixels to theoptical sheet 51. Since these two triangles are similar to each other, the relationship of the following Formula 25 holds, where X is the length of this latter triangle. -
L:f=X:S (Formula 25) - The length X of the triangle represented by Formula 25 above is nothing but the right side of Formula 24 stated before.
- Thus, in the three-dimensional
image display device 10 embodying the invention in this mode, with note taken of one point among the display pixels of thedisplay panel 2, the length X of the base of the triangle formed by the group of light rays emitted from thebacklight unit 5 and being incident on the one point among the display pixels is not shorter than the pitch V of the prismatic convexes on theoptical sheet 51 of thebacklight unit 5. - Since the prismatic convexes on the
optical sheet 51 differ in the angle of surface inclination from position to position, the directionality distribution of the lights emitted from thebacklight unit 5 also differs from one position of emission to another. For instance, where the length X of the base of the triangle is shorter than the pitch V of the convexes, the effect of the directionality distribution of emitted lights dependent on the position of convex is greater. However, since the length X of the base of the triangle is not shorter than the pitch V of the convexes in the three-dimensionalimage display device 10 of this exemplary embodiment, the effect can be eased even if the directionality distribution differs with the position of emission, because it is averaged over one cycle or more. - Further, lights having passed the one point among the display pixels and passed the
cylindrical lenses 3 a are projected on the viewing plane, and match the one point among the display pixels on a one-to-one basis. Therefore, a finite range X on theoptical sheet 51 matches a certain one point on the viewing plane, and the finite range X on theoptical sheet 51 varies matching the point on the viewing plane. It is note that with the luminance distribution of theoptical sheet 51 in a certain finite range X, if the directionality distribution, i.e. the luminance distribution, of emitted lights differs with the position of the finite range X on the optical sheet, the brightness on the viewing plane will vary from position to position. Since this variation in brightness is observed superposed over the displayed image, picture quality seriously deteriorates. - To solve this problem, it is effective to uniformize the luminance distribution in the finite range X irrespective of its position on the optical sheet. As Formula 24 holds in the three-dimensional
image display device 10 of this exemplary embodiment and the finite range X is set at or above the pitch V of the prismatic convexes on theoptical sheet 51, the luminance distribution in the finite range X can be uniformized irrespective of its position on theoptical sheet 51. This makes it possible to realize a thin image display device having excellent display quality. - Next will be described the advantages of the three-dimensional
image display device 10 with reference to a two-viewpoint three-dimensional image display device using as the display panel 2 a transmissive liquid crystal display panel of which the glass substrate (not shown) is 0.7 mm thick and the pixel pitch is 0.15 mm, by way of example. The distance between the vertex of thelenticular lens 3 and the display pixels, and the focal distance f in this three-dimensional image display device are both equal to the thickness of the glass substrate (not shown), i.e. 0.7 mm. - Further, between the display pixels and the
optical sheet 51, there are disposed, in addition to the aforementioned glass substrate (not shown), a polarizing plate (not shown), which is an important item for a transmissive liquid crystal display panel, a multi-layered optical film (not shown) for enhancing the luminance, and a light-transmissive sticky film (not shown) for fixing thebacklight unit 5 and the liquid crystal display panel to each other in this order. Their thicknesses are 0.7 mm for the glass substrate, 0.3 mm for the polarizing plate, 0.2 mm for the optical film, and 0.2 mm for the sticky film. - Therefore, the distance S from the display pixels to the
optical sheet 51, i.e. the minimum thickness to allow the arrangement of these members is 1.4 mm. According to Formula 24, by setting the convex pitch V on theoptical sheet 51 at or below 0.6 mm, the effect of the directionality distribution of the convex on theoptical sheet 51 can be eased, making it possible to realize an image display device having excellent display quality. - On the other hand, if the convex pitch V of the
optical sheet 51 is greater than 0.6 mm, the distance from the display pixels to theoptical sheet 51 should be extended to prevent deterioration in display quality. If, for instance, the convex pitch V of theoptical sheet 51 is 1 mm, greater than X, as shown inFIG. 18 , the distance S from the display pixels to theoptical sheet 51 should be 2 mm, resulting in a wasteful gap between the display pixels and theoptical sheet 51 and a consequent increase in the thickness of the image display device. - Thus, by keeping the pitch of the convexes on the
optical sheet 51 provided on thebacklight unit 5 at or below 0.6 mm, a thin three-dimensional image display device is formed having excellent display quality. -
FIG. 2 shows a perspective view of a portable terminal device mounted with the three-dimensional image display device shown in FIG. 1. As shown inFIG. 2 , this three-dimensionalimage display device 10 is mounted on a portableterminal device 9, such as a cellular phone for example. - Although an optical sheet on whose surface prismatic convexes extending in one direction are formed is used in the three-dimensional
image display device 10 of this exemplary embodiment, the invention is not limited to this configuration. For instance, two optical sheets on whose surfaces prismatic convexes extending in one direction each are formed can be so disposed on thebacklight unit 5 that the extending directions of the convexes orthogonally cross each other in a planar view. In this case, the pitch V of the optical sheets, whose convexes extend in the same direction as the arraying direction of thecylindrical lenses 3 a, may be within a range defined by Formula 24 above. - It is also possible to use an optical sheet on which prismatic convexes are arrayed in a matrix shape. For an illuminating member including an optical sheet on which convexes are formed is arranged on a backlight unit, the use of the optical sheet on which convexes are disposed in a matrix shape gives the same effect as optical sheets on which convexes extend in one direction are used in two layers. As a result, the number of constituent members can be reduced with a corresponding saving in cost.
- Although the convexes are formed on the
optical sheet 51 in the three-dimensionalimage display device 10 of this exemplary embodiment, the invention is not limited to this configuration. Where convexes are formed on the surface of a light guiding plate disposed on thebacklight unit 5 for instance, the same effect can be achieved by keeping the pitch of the convexes within the range defined by Formula 24 above. If the convexes have an in-plane distribution, then it is preferable for the minimum value of the pitch V to satisfy the requirement of Formula 24 above. Hence, the image display device could have a smaller thickness without sacrificing its display quality even if the distance V has an in-plane distribution. - Further, the shape of the convexes is not limited to being prismatic, but instead convexes could be provided on the surface of the
backlight unit 5, and the presence of the convexes results in a different directionality distribution of emitted lights in a microscopic region. Further a light dispersing member, more specifically an optical film or the like having a light scattering effect, could be formed over the convexes formed on thebacklight unit 5. This would reduce the influences of the convexes. - Although the foregoing description referred to prismatic convexes, concaves shaped like inverted prisms would prove as effective.
- Further, though a transmissive liquid crystal panel is supposed to be used as the
display panel 2 in the three-dimensionalimage display device 10 of this exemplary embodiment, the invention is not limited to this, but can be applied to any display panel using thebacklight unit 5. The liquid crystal panel can be driven by either an active matrix system such as a thin film transistor (TFT) system or the thin film diode (TFD) system, or by a passive matrix system such as the super-twisted nematic liquid crystal (STN) system. Theimage display device 1 in this exemplary embodiment can be applied not only to cellular phones or personal digital assistants (PDA) but also to various other portable terminals including game machines, digital still cameras, digital video cameras, note book computers, video players, DVD players, vending machines, monitors for medical use and ATMs (automated teller machine). - Next will be described a three-dimensional image display device, according to the second exemplary embodiment of the present invention.
FIG. 3 is an optical model diagram illustrating the three-dimensional image display device embodying the invention in this mode, andFIG. 4 shows a perspective view of a fly-eye lens. As shown inFIG. 3 , a three-dimensionalimage display device 20 of this exemplary embodiment is the same as the three-dimensionalimage display device 10 of the first exemplary embodiment described above except that a fly-eye lens 8 in which constituent lenses are formed in a matrix shape is used instead of the lenticular lens. As the three-dimensionalimage display device 20 of this exemplary embodiment uses the fly-eye lens 8, it is possible to distribute the lights of pixels transmitted through the lenses in four directions, up and down, and right and left. As a result, even if the arranging direction of the three-dimensionalimage display device 20 is turned, three-dimensional images can still be displayed. - Incidentally, where the lens pitch of the fly-
eye lens 8 differs with the arraying direction, it is preferable to keep the convex pitch V in theoptical sheet 51 is preferably within the range of Formula 24 above in the decreasing direction of the pitch. In the three-dimensionalimage display device 20 of this exemplary embodiment, as in the three-dimensionalimage display device 10 of the first exemplary embodiment described above, the convexes formed on the surface of theoptical sheet 51 may be arrayed either in one direction or in a matrix shape. - Where two
optical sheets 51 on whose surfaces prismatic convexes are formed in one direction each are so disposed that the directions of the convexes orthogonally cross each other in a planar view, the pitch V of the optical sheet on thedisplay panel 2 side is preferably within a range defined by Formula 24 above. That is, because the optical sheet on thedisplay panel 2 side is shorter in distance to the display pixels, the condition for preventing the display quality from deterioration is more stringent. - Furthermore, the other aspects of the configuration and advantages of the three-dimensional
image display device 20 of this exemplary embodiment than those described above are similar to those of the three-dimensionalimage display device 10 of the first exemplary embodiment described earlier. - Next will be described a three-dimensional image display device, which is a third exemplary embodiment of the present invention.
FIG. 5 shows a partial perspective view of the three-dimensional image display device, according to the third exemplary embodiment of the invention. Incidentally,FIG. 5 shows only part of the lenticular lens, part of the optical sheet and one pair of display pixels, but the illustration of all other constituent elements is dispensed with. - As shown in
FIG. 5 , in a three-dimensionalimage display device 30 of this exemplary embodiment, the lengthwise direction of thecylindrical lenses 3 a forming thelenticular lens 3 is not identical with the direction in which prismatic convexes formed on the surface of theoptical sheet 51 extend. The repeating pitch V of the convexes on theoptical sheet 51 satisfies the condition of the following Formula 26, where θ is the angle formed by the lengthwise direction of thecylindrical lenses 3 a with the extending direction of the prismatic convexes and Pv is the pixel pitch of thecylindrical lenses 3 a in the lengthwise direction. -
V≦L×S×(cos θ)/f+P v×(sin θ) (Formula 26) -
FIGS. 6( a) and 6(b) show schematic sectional views of the backlight unit of the three-dimensional image display device or this exemplary embodiment, whereinFIG. 6( a) is a sectional view along line A-A inFIG. 5 andFIG. 6( b), one along line B-B. In the three-dimensional image display device of this exemplary embodiment, as thelenticular lens 3 and theoptical sheet 51 are so arranged that the angle formed between the lengthwise direction of thecylindrical lenses 3 a and the extending direction of the prismatic convexes on theoptical sheet 51 be θ, the relative positions of the convex shape inFIGS. 6( a) and 6(b) differ by a value (Pv×tan θ). - The component in the arraying direction of the
cylindrical lenses 3 a at the convex pitch V of theoptical sheet 51 is a value (V/cos θ). - As the optical sheet is inclined relative to the cylindrical lenses in this exemplary embodiment, the inclination angle θ should be considered. Further, since the cylindrical lenses have no lens action in their consecutive direction (hereinafter referred to as the longitudinal direction), there is no separating action in the longitudinal direction. Thus, while there is significant separation in the arraying direction of the lenses (hereinafter referred to as the lateral direction), no separation occurs in the longitudinal direction.
- Where the optical sheet has convexes or concaves in the longitudinal direction, only the separating action of the lenses needs to be considered, but where they are arranged rotationally, the anisotropy of the lens action of the cylindrical lenses should also be considered.
- In this exemplary embodiment of the invention, the absence of separating action by the cylindrical lenses in the longitudinal direction is positively utilized. The absence of separating action in the longitudinal direction means that superposition is allowed. However, if the range of superposition surpasses the pixel pitch in the longitudinal direction, differences among pixels may occur, highly likely to result in observation of unevenness. Therefore, the range of superposition in the longitudinal direction is kept within the pixel pitch in the longitudinal direction.
- The difference in the relative position of the convex/concave shape in the lateral direction due to the inclination by the angle θ is Pv×tan θ within the longitudinal pixel pitch Pv. Conceivably, as a result of superposition in the longitudinal direction due to the cylindrical lens action and the rotational arrangement, the convex/concave pitch has been reduced correspondingly.
- As the inherent convex/concave pitch is V and the pitch in the lateral direction is V/cos θ, the pitch where the convexes/concaves are rotationally arranged relative to the cylindrical lenses is:
-
V/cos θ−Pv×tan θ - This value is to be made smaller than L×S/f as in the first exemplary embodiment of the invention.
- Since the
cylindrical lenses 3 a have no lens effect in their consecutive direction, the effect of theoptical sheet 51 can be attributed to the superposition of the convex arrangements shown inFIGS. 6( a) and 6(b). Therefore, the convexes on theoptical sheet 51 become equivalent to what they are when they are arranged with their width expanded by a value (Pv×tan θ). Further, since a component in the arraying direction of thecylindrical lenses 3 a at the convex pitch V of theoptical sheet 51 is represented by the value (V/cos θ), the three-dimensional image display device of this exemplary embodiment provides the same effect as the three-dimensionalimage display device 10 of the first exemplary embodiment described above when the following Formula 27 holds. -
V/cos θ−P v×tan θ≦L×S/f (Formula 27) - Additionally, Formula 27 above can be rearranged into Formula 26 stated earlier. The three-dimensional
image display device 30 of this exemplary embodiment is made thinner and superior in display quality by arranging theoptical sheet 51 on which convexes extending in one direction are formed at an inclination relative to the lengthwise direction of thecylindrical lenses 3 a, and thereby utilizing the one-dimensional lens action of the cylindrical lenses to prevent deterioration in display quality attributable to the convexes of theoptical sheet 51. - While the
optical sheet 51 in the three-dimensional image display device of this exemplary embodiment is arranged rotated relative to the lengthwise direction of thecylindrical lenses 3 a, it is sufficient for the extending direction of the convexes on theoptical sheet 51 not to be identical with the lengthwise direction of thecylindrical lenses 3 a. - For instance, the
optical sheet 51 can be so arranged that the extending direction of its convexes be parallel to a certain side of the three-dimensional image display device with thelenticular lens 3 being arranged rotated. However, as an inclined arrangement of thelenticular lens 3 would make the user feel awkward, thelenticular lens 3 can be arranged so that the lengthwise direction of thecylindrical lenses 3 a is parallel to one side of the display panel. This could relieve the user from the sense of awkwardness. - Further, a light dispersing member may as well be disposed between the display panel and the
optical sheet 51. This can ease the influence of the directionality distribution of emitted lights attributable to the convexes of theoptical sheet 51 on displayed images. As a result, a thin image display device having excellent in display quality can be obtained. - Next will be described a three-dimensional image display device, which is a fourth exemplary embodiment of the present invention.
FIG. 7 shows a partial perspective view of the three-dimensional image display device of this exemplary embodiment of the invention. Incidentally,FIG. 7 shows only part of the lenticular lens, part of the optical sheet and one pair of display pixels, but the illustration of all other constituent elements is dispensed with. As shown inFIG. 7 , a three-dimensionalimage display device 40 of this exemplary embodiment has anoptical sheet 52 on which convexes are formed in a matrix shape instead of theoptical sheet 51 on which convexes extending in one direction are formed. Incidentally, other aspects of the configuration of the three-dimensionalimage display device 40 of this exemplary embodiment are similar to the three-dimensionalimage display device 30 of the third exemplary embodiment described above. - In the three-dimensional
image display device 40 of this exemplary embodiment, the lengthwise direction of thecylindrical lenses 3 a is not identical with the direction in which prismatic convexes formed on the surface of theoptical sheet 52 extend, and the pitch Vv of the convexes inclined relative to the extending direction of thecylindrical lenses 3 a at an angle θ satisfies the condition of the following Formula 28. Incidentally, Pv in the following Formula 28 represents the pixel pitch in the lengthwise direction of thecylindrical lenses 3 a. -
V v×cos θ≦Pv (Formula 28) - This exemplary embodiment, as does the third exemplary embodiment, improves display quality by utilizing the anisotropy of the lens action of the cylindrical lenses. Thus, the use of the principle of superposition in the longitudinal direction necessitates definition of the pitch in the longitudinal direction.
- In the
optical sheet 52 on which convexes are formed in a matrix shape, the pitch of convexes projected in the longitudinal direction is Vv×cos θ where Vv is the convex pitch and θ is the angle of rotation of the sheet. Since a plurality of convexes can be arranged per pixel if this value is not more than the pixel pitch Pv in the longitudinal direction, the influence of the convexes can be reduced. - Although the convex pitch in the lateral direction is prescribed and made extremely fine in the first and second exemplary embodiments, making it fine only in the lateral direction would invite an imbalance and make the manufacturing of the device more difficult, the effect in the longitudinal direction is also utilized.
- Since this enables each pixel (the right-
eye pixel 42 or left-eye pixel 41) to cover two or more convexes, it is made possible to equivalently enhance the spatial frequency of the convexes through the one-dimensional lens action of thecylindrical lenses 3 a and thereby to prevent deterioration in display quality attributable to the convexes. - The three-dimensional
image display device 40 of this exemplary embodiment is made thinner and superior in display quality by disposing anoptical sheet 52 on which convexes extending in one direction are formed in a matrix shape at an inclination relative to the lengthwise direction of thecylindrical lenses 3 a and thereby utilizing the one-dimensional lens action of the cylindrical lenses to prevent deterioration in display quality attributable to the convexes. - The use of the
optical sheet 52 on which convexes are formed in a matrix shape gives the same effect as two optical sheets on which convexes extend in one direction are used. As a result, the number of constituent members can be reduced with a corresponding saving in manufacturing cost. - Next will be described a three-dimensional image display device, which is a fifth exemplary embodiment of the present invention.
FIG. 8 is an optical model diagram illustrating the three-dimensional image display device of this exemplary embodiment. InFIG. 8 , with a view to making the diagram easier to perceive, the illustration of other constituent elements than pixels on thedisplay panel 2 is dispensed with. In a three-dimensional image display device 50 of this exemplary embodiment, the foci of thecylindrical lenses 3 a forming thelenticular lens 3 are set closer than the display pixels toward thelenticular lens 3 with the result that the focal distance f is shorter than the distance H between the vertexes of the lenses and the pixels. Thus the following Formula 29 holds. -
f<H (Formula 29) - In the three-dimensional image display device 50 of this exemplary embodiment, as the foci of the
lenses 3 a are set closer than the display pixels toward thelenticular lens 3, light rays in a broader range on thebacklight unit 5 may be used. - As a result, an optical sheet longer in the convex pitch can be used, and accordingly the influence of the directionality distribution of emitted lights attributable to the convexes can be eased. Further, as the focal positions of the lenses are off the pixel surface, the influence of the non-display areas between pixels can be eased, and accordingly the deterioration of displayed images attributable to the non-display areas can also be prevented. Additionally, the other aspects of the configuration and advantages of the three-dimensional image display device 50 of this exemplary embodiment than those described above are similar to those of the three-dimensional
image display device 10 of the first exemplary embodiment described earlier, though the distance from the lens focal position to theoptical sheet 51 in the three-dimensional image display device 50 of this exemplary embodiment is represented by S. - Next will be described a three-dimensional image display device, which is a sixth exemplary embodiment of the present invention.
FIG. 9 is an optical model diagram illustrating the three-dimensional image display device of this exemplary embodiment. In the three-dimensional image display device of this exemplary embodiment, the foci of the lenses forming the fly-eye lens 8 are set closer than the display pixels toward the fly-eye lens 8 with the result that the focal distance f is shorter than the distance H between the vertexes of the lenses and the pixels. Accordingly the followingFormula 30 holds. Additionally, the other aspects of the configuration of a three-dimensionalimage display device 60 of this exemplary embodiment are the same as those of the three-dimensionalimage display device 20 of the second exemplary embodiment described above. -
f<H (Formula 30) - In the three-dimensional
image display device 60 of this exemplary embodiment, as the focal positions of the lenses are set closer than the display pixels toward the fly-eye lens 8, light rays in a broader range on thebacklight unit 5 can be used in addition to the effects of the three-dimensionalimage display device 20 of the second exemplary embodiment described above. As a result, an optical sheet longer in the convex pitch may be used, and accordingly the influence of the directionality distribution of emitted lights attributable to the convexes can be eased. Further, as the focal positions of the lenses are off the pixel surface, the influence of the non-display areas between pixels can be eased, and accordingly the deterioration of displayed images attributable to the non-display areas can also be prevented. - The three-dimensional image display devices of the first through sixth exemplary embodiments may as well be two-dimensional image display devices. Such an image display device, where it is mounted on portable terminal device for instance, the user can watch images for a plurality of points of view by merely varying the angle of the portable terminal device. Especially where the images for the plurality of points of view are correlated, each image can be viewed by a simple method of changing the angle of viewing, resulting in a substantial improvement in convenience. Or where images for a plurality of points of view are arrayed in the longitudinal direction, the viewer can watch the image for each point of view with two eyes all the time, resulting in improved perceptibility of the image for each point of view. Also, a liquid crystal display panel may be used as the display panel.
- Next will be described at portable terminal device, which is a seventh exemplary embodiment of the present invention.
FIG. 10 shows a perspective view of the portable terminal device of this exemplary embodiment, andFIG. 11 is an optical model diagram illustrating the operation of an image display device mounted on the portable terminal device embodying the invention in this mode. - As shown in
FIG. 10 andFIG. 11 , a portableterminal device 9 of this exemplary embodiment is a cellular phone with animage display device 70 built into it. In this portableterminal device 9, the arraying direction of thecylindrical lenses 3 a forming thelenticular lens 3 is alongitudinal direction 11, i.e. the vertical direction of images, and the lengthwise direction of thecylindrical lenses 3 a is alateral direction 12, i.e. the horizontal direction of images. The arraying direction of the first-viewpoint pixels 43 and the second-viewpoint pixels 44 in one pair of display pixels of the display panel is alongitudinal direction 11, the same as the arraying direction of thecylindrical lenses 3 a. Incidentally, though only four of thecylindrical lenses 3 a are shown inFIG. 10 with a view to simplifying the illustration, actually as manycylindrical lenses 3 a as the arrays of display pixels in thelongitudinal direction 11 are formed. The other aspects of the configuration of theimage display device 70 in the portableterminal device 9 of this exemplary embodiment are the same as those of the three-dimensionalimage display device 10 in the first exemplary embodiment described earlier. - Next will be described the operation of the
image display device 70 in the portableterminal device 9 of this exemplary embodiment. As shown inFIG. 11 , thebacklight unit 5 emits lights, which are incident on thedisplay panel 2. Then, the first-viewpoint pixels 43 of thedisplay panel 2 display a first-viewpoint image, and the second-viewpoint pixels 44 display a second-viewpoint image. The lights being incident on the first-viewpoint pixels 43 and the second-viewpoint pixels 44 of thedisplay panel 2 are transmitted by these pixels, and travel toward thelenticular lens 3. These lights are refracted by thecylindrical lenses 3 a of thelenticular lens 3, and are emitted toward areas E1 and E2. The areas and E1 and E2 are arrayed in thelongitudinal direction 11. If then the viewer positions his eyes on the area E1, he can view the first-viewpoint image or, if he positions his eyes on the area E2, he can view the second-viewpoint image. - The portable
terminal device 9 of this exemplary embodiment has an advantage that the viewer can position both his eyes on the area E1 or E2 by merely varying the angle of the portableterminal device 9, and thereby watch the first-viewpoint image or the second-viewpoint image. Especially where the first-viewpoint image and the second-viewpoint image are correlated, he can view each image by a simple method of changing the angle of viewing, resulting in a substantial improvement in convenience. - Incidentally, if images for a plurality of points of view were arrayed in a lateral direction, there would be a position where the right eye and the left eye see images from different points of view, and the viewer would be so confused as to be unable to perceive the image from each point of view. Where images for a plurality of points of view are arrayed in the longitudinal direction as in this exemplary embodiment of the invention, the viewer can always watch images for different points of view with both eyes and accordingly can readily perceive these images. Other advantages of the portable
terminal device 9 of this exemplary embodiment are similar to those of the three-dimensional image display device of the first exemplary embodiment described earlier. This seventh exemplary embodiment can as well be applied to the three-dimensional image display devices of the third, fourth and fifth exemplary embodiments described above. - The previous description of embodiments is provided to enable a person skilled in the art to make and use the present invention. Moreover, various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles and specific examples defined herein may be applied to other embodiments without the use of inventive faculty. Therefore, the present invention is not intended to be limited to the embodiments described herein but is to be accorded the widest scope as defined by the limitations of the claims and equivalents.
- Further, it is the inventor's intent to retain all equivalents of the claimed invention even if the claims are amended during prosecution.
Claims (4)
1. An image display device, comprising:
a display panel in which a plurality of display units including at least pixels for displaying an image for a first point of view and a second point of view are arrayed;
a lens for distributing lights transmitted through pixels for said first point of view and lights transmitted through pixels for said second point of view into mutually different directions;
a backlight which has a plurality of convexes or concaves which refract lights; and
a light dispersing member disposed between said display panel and said backlight.
2. The image display device according to claim 1 , wherein a focal distance of said lens is shorter than a distance between said lens and said pixels.
3. The image display device according to claim 1 , wherein said lens comprises a lenticular lens in which a plurality of cylindrical lenses are so arrayed as to be in parallel with one another in their lengthwise direction.
4. The image display device according to claim 1 , wherein said lens comprises a fly-eye lens in which a plurality of convex lenses are arrayed in a matrix shape.
Priority Applications (1)
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US12/071,340 US20080218867A1 (en) | 2004-06-30 | 2008-02-20 | Image display device and portable terminal device |
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JP2004193095A JP4196889B2 (en) | 2004-06-30 | 2004-06-30 | Image display device and portable terminal device |
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US11/168,932 US7420741B2 (en) | 2004-06-30 | 2005-06-29 | Image display device and portable terminal device |
US12/071,340 US20080218867A1 (en) | 2004-06-30 | 2008-02-20 | Image display device and portable terminal device |
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US11/168,932 Continuation US7420741B2 (en) | 2004-06-30 | 2005-06-29 | Image display device and portable terminal device |
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Also Published As
Publication number | Publication date |
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CN100351674C (en) | 2007-11-28 |
CN101158751A (en) | 2008-04-09 |
JP2006017820A (en) | 2006-01-19 |
JP4196889B2 (en) | 2008-12-17 |
US20060001974A1 (en) | 2006-01-05 |
US7420741B2 (en) | 2008-09-02 |
CN1734311A (en) | 2006-02-15 |
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