WO2001092955A1

WO2001092955A1 - Attachment for video projectors used for the 3-d projection of stereoscopic images

Info

Publication number: WO2001092955A1
Application number: PCT/EP2001/005950
Authority: WO
Inventors: Stefan Naumann; Rudolf Friedemann; André Volke; Hans-Joachim Cornelius
Original assignee: Codixx Ag
Priority date: 2000-05-31
Filing date: 2001-05-23
Publication date: 2001-12-06
Also published as: AU5677300A; AU2001260330A1; DE10192272D2; DE10192272B4; WO2001092954A1

Abstract

The invention relates to an attachment for a light-emitting video projector, whose beam incorporates a respective left and right stereoscopic field arranged spatially next to one another. The projector is used to project 3-D stereoscopic images on a projection surface, on which the projection planes are retained to a great extent, said images being viewed with a pair of polarisation glasses. The aim of the invention is to develop an attachment of this type, which overcomes the disadvantages of prior art and which is used to create stereoscopic images on a projection surface, on which the polarisation planes are retained to a great extent, said images being viewed with a pair of simple polarisation glasses. To achieve this, the attachment in one embodiment consists of at least two rotative mirrors (2), in addition to a filter comprising a retardation film (3) for rotating the polarisation direction of the light through 90° and the retardation filter (3) and the two mirrors (2) are aligned in relation to one another in such a way, that only the polarisation direction of the light beam of one of the two stereoscopic fields is rotated by the retardation filter (3) and both stereoscopic fields are projected in a superimposed manner on the projection surface (5).

Description

ATTACHMENT FOR VIDEO PROIEECTORS FOR THE 3-D PROTECTION OF STEREO IMAGES

The invention relates to an attachment for video projectors for 3-D projection of stereo images according to the preambles of claims 1, 4, 8, 12.

Stereo images, in particular moving stereo images, are, according to the known state of the art, expensive hardware, such as Workstations with 3-D graphics options and frequency-controlled LC glasses, accessible on screen or through the use of expensive multi-beam devices for projection surfaces (US 45 04 856 and IWASAKI et al. 3-dimensional personal computer system, in: IEEE Transactions on Consumer, Electronics, Vol. 34, No. 3 August 1988, pp. 536-542).

Alternative solutions by using an optical attachment for single-beam video projectors were presented as a prism construction in JP 09281616 or as a mirror construction in DE 196 08 362.

DE 195 25 871 CI also describes devices for recording and reproducing electronic spatial images by means of a video camera or a video projector. The video projector attachment for the reproduction of the spatial images consists of an elaborate mirror prism construction with two polarization filters.

The object of the invention is to develop a generic attachment with which the disadvantages of the prior art are avoided and with which stereo images are generated on a projection surface on which the polarization planes are largely maintained, which are viewed with simple polarization glasses can. According to the invention, this object is achieved by the features of claims 1, 4, 8 and 12. The attachment according to claim 1 is characterized in that at least two rotatably arranged mirrors and a filter with a retardation film for rotating the direction of polarization of the light by 90 ° are provided and the retardation filter and the two mirrors are adjusted relative to one another such that only the light beam of one of the two stereo fields is rotated in its polarization direction by the retardation filter and both stereo fields are projected onto one another on the projection surface.

The attachment according to claim 4 is provided for an unpolarized light and / or linearly polarized light-emitting single-beam video projector, in the beam of which a left and a right stereo field are spatially arranged next to one another for 3-D projection of stereo images onto a Projection area, in which the polarization planes are largely retained, for viewing with polarization glasses, the attachment being formed from at least one movable mirror for one stereo field and from a beam splitter such as Nicols prism for the other stereo field.

The attachment according to claim 8 is provided for a light-emitting single-beam video projector, in the beam of which a left and a right stereo field are arranged spatially next to one another, for 3-D projection on a projection surface for viewing with polarizing glasses, whereby the prefix of one unit for generating linearly polarized light for the left and the right field, one unit for superimposing the two fields, one optical component for rotating the polarization plane by 90 °, and one unit for mixing the two vertically fields polarized to one another is formed. In this embodiment, different polarized light can be used depending on the wavelength (linear, partial, elliptical circular, unpolarized). With the embodiment, an exactly superimposed image is achieved with reduced adjustment effort.

In a preferred embodiment of this variant of the attachment, the attachment consists of one beam splitter for each stereo field, one mirror for each stereo field, and one retardation filter (λ / 2 plate) for each half of each stereo field , each from an optical element per stereo field, which superimposes two parallel beam paths to one beam output, from further mirrors and from another beam expensive, which together form the two stereo fields with their complementary polarization planes to form a stereo -mix the coded output image, the optical elements being arranged in such a way that the polarization planes of each stereo field are separated, one of the two separated components is rotated, the components are mixed into a parallel beam path so that for each Stereo field an image with polarization plane rotated by 90 ° e It depends on which are mixed via the further beam splitter.

In a further embodiment according to claim 12, a trapezoidal distortion is avoided in that one field is mirrored and projected on the vertical between the two stereo fields in order to ensure distortion-free projection onto one another, and the other field is generated as a mirror image is, the mirror projection of the mirror-generated field is carried out with the help of an isosceles 90 ° prism and the separation of the two fields is achieved by different polarization. Appropriate embodiments are specified in the subclaims.

The advantages achieved with the invention are, in particular, that the previous constructions are considerably simplified and the quality of the 3-D image reproduction is significantly improved. This is mainly achieved by eliminating a fixed mirror and two polarization filters and using a retardation filter. This makes the light absorption of one stereo field clear and that of the other even to zero, so that more brilliant 3-D images are projected. This also has the positive effect that presentation rooms no longer have to be darkened as much as before. In addition, the adjustment effort in the attachment according to the invention is less. In principle, the attachment can be placed on any LCD single-beam video projector. The stereo fields generated spatially next to one another with graphics software or a stereo camera can alternatively be displayed from a video cassette or on-line by PC or graphics workstation via the video projector.

The resolutions according to the invention provide easy access to the projection of moving stereo images, in particular for lecturing in teaching, research, school lessons. Such presentations are of particular interest for the mediation of spatial vision of moving images in chemistry, biochemistry, medicine and architecture.

The invention is explained in more detail below using exemplary embodiments of attachments. In the accompanying drawing: 1: the schematic representation of a first embodiment of the attachment,

Fig. 2: the schematic representation of a second embodiment of the attachment, Fig. 3: the schematic representation of a third

Embodiment of the header,

Fig. 4: the schematic representation of a variant of the third embodiment according to Fig. 3,

5: the schematic representation of a fourth embodiment of the attachment,

6: the schematic representation of an embodiment of a mixing unit,

Fig. 7: the schematic representation of a projection onto one another of two partial images with almost no keystone distortion and

Fig. 8: the schematic representation of an arrangement for mirroring and projection according to Fig. 7.

According to the illustration in FIG. 1, in a first embodiment of the invention, the optical attachment for a linearly polarized light-emitting video projector 1 consists of two rotatably arranged mirrors S and a correspondingly positioned filter with a retardation film 3, which thus adjusts to one another are that the direction of polarization of the light beam is only rotated by 90 ° from a stereo field. The two stereo fields of the stereoscopic representation generated side by side are projected onto one another on a projection surface PF. A diaphragm 4 is arranged on the attachment in such a way that disturbing reflections caused by scattered light from the attachment on the edges of the projection surface are prevented. 3-D images can be viewed with the aid of simple polarization glasses and using a polarized light-reflecting projection surface PF.

Cheap, light-scattering plastic films can also be used as a reflecting projection surface PF which maintains the polarization planes, instead of expensive screens.

An advantageous embodiment of the attachment according to claim 1 provides that, as shown in FIG. 2, the mirror S2 applied in the region of the lens center is semitransparent and the further mirror S1 is a surface mirror. The mirrors S1, S2 can be rotated a few degrees perpendicular to the projection plane in order to place the left stereo field LB over the right stereo field RB on the projection surface PF.

Is projected onto the projection surface PF1, then ^'the right half and the left image RB LB field can be adjusted separately.

When projecting onto the projection surface PF2, only the left field LB can be adjusted. Only the left field LB is moved, the right field RB is projected directly through the semi-transparent mirror S2. For the right field RB, the semi-transparent mirror S2 functions as a transparent medium and for the right field RB as a reflector, both fields RB, LB are each reflected once, so that a mirror-inverted image results, which can be relativized by software or hardware. The beam path is illustrated for the left field LB with solid lines and for the right field with dashed lines.

In this embodiment according to FIG. 2, the right field RB is projected directly and the left field is reflected twice, so that the projected images on the projection surface PF do not appear mirror-inverted, but appear in real representation.

A prerequisite for using this variant of the embodiment of the attachment is that the light of the left and right fields LB and RB are polarized perpendicular to one another. There are two options here, depending on whether the projector emits linearly polarized light or not. In the first case, the polarization plane of the light has to be rotated by 90 °. This can be achieved, for example, with a retardation film or retarder R (bold, dashed), which should have the position as indicated in FIG. 1. These retarders R are almost transparent, so that almost no light loss would result from additional polarization.

Various other known elements such as λ / 2 plates can also be used as optical components for rotating the polarization plane by 90 °.

In the second case, polarizers P1 and P2 (bold, dotted) would have to be inserted between the projection lens and the attachment in such a way that the left and right fields LB and RB are polarized at 90 ° to one another. The retarder R can also be arranged at the position P1 or P2. If the mirror S2 is shifted to the right by one field width, then a totally reflecting mirror should be used instead of the semi-transparent mirror S2. The path for both drawing files is the same length. Except for unavoidable optical losses at the interfaces / reflectors, the full brightness is used. There is no color dispersion through semi-transparent mirrors, the partial images can be adjusted independently.

This embodiment according to FIG. 2 allows a more compact design of the attachment compared to the embodiment according to FIG. 1.

Another embodiment of the attachment according to the invention is shown in Fig. 3. In this embodiment, unpolarized light or light with a defined position of the vibration plane is a prerequisite for use. The setup consists of a surface mirror S that can be rotated a few degrees perpendicular to the projection plane and a beam splitter B that can be moved in the same way. The beam paths for the left field LB (continuous, thin line) and the right field RB (thin, dashed line) are analogous to Embodiment according to FIG. 2. In addition, the polarization planes for the rays of the two fields after exiting beam splitter B are illustrated in FIG.

This variant assumes that the projector either emits unpolarized light or linearly polarized light in such a way that all colors of the visible spectrum lie in one and the same polarization plane and that this plane has a defined angle to the beam splitter. When linearly polarized light emitting projectors is disposed a retarder R between the lens output for the left half image Lb and the mirror S or lens output for the right half-image ^¬ RB and the B beam splitter or mirror S and 5 Beam splitter.

When projecting onto the projection surface PF1, the beam splitter B acts as a transparent, polarizing medium for the left field LB and as a for the right field RB

_10th reflective, polarizing medium. The planes of polarization of both fields RB, LB are perpendicular to one another. Analogously to the embodiment according to FIG. 2, both fields are reflected here once, so that a mirror-inverted 3D image is produced.

15

When projecting onto the projection surface PF2, the beam splitter B acts as a reflecting, polarizing medium for the left field LB and as a transmissive, polarizing medium for the right field RB. Here, too, the polarization planes of the two images are perpendicular to each other, but in the opposite way. In this case, the left field LB is reflected twice, so that no mirror image is created. 5 If a projector emits linearly polarized light, but the polarization plane is not formed at the correct angle, then by using a flat, unstructured LC cell, the polarization plane can be adjusted by adjusting the amplitude of the 0 changes applied to the LC cell -voltage the polarization plane is rotated so that it lies in the required plane. Alternatively, a λ / 2 plate acting as a retarder can also be used at a correspondingly adapted angle of the crystal axis to the polarization plane. 5 The structure of the attachment in the embodiment according to FIG. 4 consists of the same components as the embodiment according to FIG. 3, but positioned differently.

Here, too, are the ray profiles for the right field

RB (dashed, thin) and for the left field LB

(continuous, thin) and their polarization directions

Exit from the beam splitter B clarifies analogous to the embodiment of FIG. 3. In the central area, where both fields overlap on the projection surface PF in area 2, the spatial image is created. Both fields are reflected once, so that a mirror-inverted 3D image is created. The requirements for the light that the projector emits are the same as in the embodiment according to FIG. 3.

A variant of this embodiment shown in FIG. 4 could consist in that the mirror S is arranged parallel downward shifted, that is, under the lower left corner of the beam splitter B, and that a retarder R is arranged when the projector 1 emits linearly polarized light and the pole plane is at the correct angle to beam splitter B.

In principle, it applies to all the variants listed here that the projection surface or projection wall can be a reflective or a transmissive medium, so that they can be used for front and rear projections. The prerequisite for this is that these media do not have a depolarizing effect for the entire spectrum of visible light or that they change the polarization level at individual frequencies.

Furthermore, all of the variants listed here can also be applied to multi-beam projection systems to generate a three-dimensional image. In the embodiment according to FIG. 5, the attachment consists of one unit 11, 21, 31, 41; 12, 22, 32, 42 for generating linearly polarized light for the left and right fields and a unit 21, 22 for superimposing the two fields. To avoid imaging errors, the path lengths for both fields are of the same length. Before mixing, the polarization plane of the one partial image is rotated to the polarization plane of the second partial image such that after mixing the one partial image has a polarization plane rotated by 90 ° to the other partial image.

The unit 11, 21, 31, 41; 12, 22, 32, 42 for generating the linearly polarized light works in such a way that, regardless of the polarization state of the incident light, linearly polarized light of a defined position of the polarization plane emerges at the output. All polarization components of the light in the incident light occur in the same ratio as in the incident light (ie, if 30% of the light is horizontally polarized or 70% vertical, then the horizontally polarized component bears 30% and the vertically polarized component 70%. to the intensity of the outgoing light). This means that projectors that emit differently polarized light depending on the wavelength can also be used (e.g. typical poly-Si TFT projectors).

A unit for mixing 13, 33, 34, 35 of the differently polarized partial images is arranged in such a way that the two partial images polarized perpendicular to one another are superimposed on one another (with the same parallax angles), so that no further adjustment work is necessary. The attachment only has to be aligned parallel to the center beam and horizontally parallel to the lower or upper image edge of the light emitted by the projector and approximately in the center of the lens. The unit for generating the polarized light consists of a beam splitter 11 to 13, which divides the incident light into its two components. In the further beam path of the two partial beams, mirrors and / or prisms 21, 22 are arranged such that they are blended again one above the other, the path lengths of both partial beams being of equal length. An optical component, for example a λ / 2 plate 41, 42, is arranged in the beam path of a partial beam for rotating the polarization plane by 90 °, so that after the two partial beams have been superimposed, linearly polarized light is available, whereby Shares are retained proportionately. If the component for rotating the polarization plane in the otherwise symmetrically constructed unit for the second partial image is arranged in the other partial beam, the polarizing plane of the outgoing light is rotated by 90 ° to that of the first partial image.

In the further beam path of the partial images, mirrors 31 to 35 are arranged in such a way that they fall into a beam splitter at an angle of 90 °, which is arranged in such a way that the two partial images are blended exactly one above the other, which is possible because a ) the path length of the beam paths of the two partial images is the same and b) the polarization plane of the partial images is rotated by 90 ° to one another. In one embodiment variant (not shown), the unit for rotating the polarization planes can also be omitted.

As shown in FIG. 6, the mixing unit can be formed, for example, from a semi-transparent mirror 211, a mirror 212 and an absorbent surface 213. An advantage over the known prior art is the fact that here it is not a prerequisite that, as in other mixing methods, both partial beams enter the common output beam in equal parts. In the previously described embodiments of the attachment or the projection methods used, either both fields are mirror-inverted or neither of the fields is mirror-inverted. Due to the asymmetry (except for the embodiment according to FIG. 8) or the superimposition of the fields arranged next to one another, an uneven, opposite trapezoidal distortion occurs.

This trapezoidal distortion can be avoided by mirroring and projecting a field at the dividing line (vertical mirror plane VS) to the other field (FIG. 7). FIG. 7a shows the unmanipulated projection of both fields, and FIG. 7b) shows the projection of both fields onto one another with almost no keystone distortion on the vertical mirror plane VS.

The reflection and projection is achieved, for example, by an isosceles 90 ° prism 5 which, as illustrated in FIG. 8, is inserted into the beam path of a field.

The isosceles 90 ° prism 5 has the effect that the light (beam path SG) is refracted towards the hypotenuse H upon entry into the prism 5 and is totally reflected there. The projection angle of the reflected field is inverted so that it is almost identical to the projection angle of the other, non-reflected field, which corresponds to a projection on top of one another. The separation of the two fields is achieved by different polarization, as was described in the previous exemplary embodiments, for example by means of a polarizer P and a λ / 2 retarder R according to FIG. 8. With this type of stereo projection, a field must have been generated with a vertical mirror image, which is not a problem with common animation software, or can be achieved by partially interchanging pixels.

REFERENCE NUMBERS

1 projector

2 area

3 retardation filters

4 aperture

5 prism 1 beam splitter 2 beam splitter 3 beam splitter 1 mirror / prisms 2 mirrors / prisms 1-35 mirrors 1.42 λ / 2 plate

211 Semi-transparent mirror

212 mirrors

213 Absorbent surface

PF projection area

LB left field

RB right field

S mirror

B Beam splitter (beam splitter

R λ / 2 retarders

VS Vertical mirror plane

SG beam path

H hypotenuse

Claims

claims

1.Attachment for a linearly polarized light-emitting video projector, in the beam of which a left and a right stereo field are arranged spatially next to each other, for 3-D projection of stereo images on a projection surface, on which the projection planes are largely retained, for viewing with polarization glasses, the attachment consisting of at least two rotatably arranged mirrors (S) and a filter with a retardation film (3) for rotating the direction of polarization of the light by 90 °, and the retardation filter (3) and the two mirrors (S) to one another are adjusted so that only the light beam of one of the two stereo fields is rotated in its polarization direction by the retardation filter (3) and both stereo fields are projected onto one another on the projection surface (PF).

2. Attachment according to claim 1, characterized in that an aperture (4) is attached to the attachment in such a way that disturbing reflections caused by scattered light from the attachment on the edges of the projection surface (PF) are prevented.

3. Attachment according to claim 1, characterized in that the mirror (S2) attached in the region of the lens center is semipermeable.

4. Attachment for an unpolarized light and / or linearly polarized light emitting single-beam video projector, in the beam of which a left and a right stereo field are arranged spatially next to each other for 3-D projection of stereo images on a projection surface in which the polarization planes are largely maintained for viewing with polarization glasses, the attachment being formed from at least one movable mirror (S) for one stereo field and from a beam splitter (B) such as Nicols prism for the other stereo field.

5. A header according to claim 4, characterized in that the beam splitter (B) covers one of the two stereo fields and the mirror (S) covers the other stereo field.

6. A header according to claim 4, characterized in that the beam splitter (B) takes up both stereo fields and that the mirror (S) is arranged such that the field desired for the image is reflected on the projection surface.

7. Attachment according to claims 4 to 6, characterized in that a diaphragm (4) is attached to the attachment in such a way that disturbing reflections caused by scattered light from the attachment on the edges of the projection surface (PF) are prevented.

8. Attachment for a light-emitting single-beam video projector, in the beam of which a left and a right stereo field are arranged spatially next to each other, for 3-D projection on a projection surface for viewing with polarized glasses, the attachment consisting of one unit (11 , 21, 31, 41; 12, 22, 32, 42) for generating linearly polarized light for the left and right fields, a unit (21, 22) for superimposing the two fields, from an optical component for rotating the plane of polarization by 90 °, is formed from a unit (211, 212, 213) for mixing the two fields polarized perpendicular to one another.

9. A header according to claim 8, characterized in that one beam splitter for each stereo field, one mirror for each stereo field, one retardation filter (λ / 2 plate) for each half of each stereo field, one each Optical element per stereo field, which superimposes two parallel beam paths to form a beam output, further mirrors and a further beam splitter, which together mix the two stereo fields with their polarization planes that are complementary to one another, are provided, the optical elements being such are arranged to each other so that the polarization planes of each stereo field are separated, one of the two separated components is rotated, the components are mixed into a parallel beam path in such a way that for each stereo field an image with a polarization plane rotated by 90 ° is created, which over the further beam splitter to a ge mixed picture.

10. An attachment according to claims 8 and 9, characterized in that the mixing unit is formed of a semi-transparent mirror ^¬ (211), a mirror (212) and an absorbing surface (213).

11. Attachment according to claims 8 to 10, characterized in that an aperture (4) is attached to the attachment in such a way that disturbing reflections caused by scattered light from the attachment on the edges of the projection surface (PF) are prevented.

12. Attachment for a light-emitting single-beam video projector, in the beam of which a left and a right stereo field are arranged spatially next to each other, for 3-D projection on a projection surface for viewing with polarized glasses, with a vertical (VS) essentially one field is mirrored and projected parallel to the beam path in order to ensure a distortion-free projection onto one another, and the other field is generated as a mirror image, and the separation of the two fields is achieved by different polarization.

13. Attachment according to claim 12, characterized in that the reflection projection of the mirror-generated stereo field is carried out by arranging an isosceles 90 ° prism (5) directly behind the projector (1).