WO1997025646A1

WO1997025646A1 - Head mounted display system with solid block optical element having internal reflective surfaces

Info

Publication number: WO1997025646A1
Application number: PCT/US1996/020719
Authority: WO
Inventors: Gregory L. Heacock; George W. Cone
Original assignee: Virtual Vision, Inc.
Priority date: 1996-01-11
Filing date: 1996-12-20
Publication date: 1997-07-17

Abstract

A head mounted display (10) includes an optical element having a solid body that is mounted on a frame (12), supporting a display (14), that is to be worn on a user's head. The optical element (16) includes an internal partially reflective coating (60) that is disposed at a 45° angle with respect to the display (14) and through which a user looks to view an image of the displayed information as superimposed on the real world. The solid optical element (16) has a focusing surface (62) that is shaped to magnify the image of the displayed information wherein the focusing surface (62) has a central axis that is co-axial with an axis of the display (14) and that is perpendicular to the visual axis along which the user looks to perceive the projected image. The optical element (16) is extremely rugged and projects a virtual image without ghost images while allowing the user to simultaneously view the real world.

Description

HEAD MOUNTED DISPLAY SYSTEM WITH SOLID BLOCK OPTICAL ELEMENT HAVING INTERNAL REFLECTIVE SURFACES

FIELD OF INVENTION

The present invention relates to a head mounted display system and more particularly to a head mounted display system having a solid block optical element with an internal reflective surface to project a non-distorted image of displayed information without ghost images.

BACKGROUND OF THE INVENTION

Head mounted display systems are known having various optical arrangements that include a number of mirrors and lenses mounted on a support with respect to an image source that displays information where the support is worn on the user's head. Typically, the mirror and lens surfaces are exposed and thereby subject to dirt and scratches that can substantially interfere with the projection of the displayed information. These systems are also extremely fragile. Although they may be suitable for use by a pilot who is confined to one position in an aircraft, they are not suitable for environments wherein the user is not constrained in his movements or is not used to dealing with delicate objects.

United States Patent No. 3,059,519 shows an optical assembly in the form of a solid block having a curved optical surface for magnifying a displayed image wherein the curved optical surface is in the direct line of sight of the user and forms a portion of a see-through optical arrangement. This type of optical assembly is very difficult to manufacture. Variations in the thickness or curvature of the optical element do not have a dramatic effect on the displayed information, but can render the user's view of the real world through the optic distorted or out of focus. Distortion in the user's view of the real world substantially defeats the purpose of a see- through optical assembly in which a clear view of the real world through the optic is desired as well as an undistorted displayed image.

Other, known head mounted display systems have included a partially reflective mirror placed in the optical path at an angle of 45° to the direct line of sight of the user. However, these mirrors are known to produce ghost images due to the thickness of the mirror. The thickness of the partially reflective mirror in such an arrangement must be substantial so that the optical assembly has structural integrity. Ghost images, however can be extremely disturbing because they interfere with the fine details of displayed images, such as alphanumeric or textural images.

SUMMARY OF THE INVENTION

In accordance with the present invention, the disadvantages of prior head mounted display systems have been overcome. The head mounted display system of the present invention includes a solid block optical element having internally reflective surfaces so as to be extremely rugged yet easily and cost effectively manufactured to project a non-distorted image of displayed information without ghost images. More particularly, the head mounted display system of the present invention includes a support to mount the system on a user's head and a display mounted on the support for displaying information. An optical element having a solid body is mounted on the support with respect to the display. The solid optical element has a partially reflective coating at an approximately 45° angle with respect to the display and through which a user looks to view an image of the displayed information. The solid optical element has a focusing surface that is shaped to magnify a displayed image wherein the focusing surface is coaxial with the display and normal to the central see-through axis of the optical element.

Because there is no optical element on the see-through axis that adds optical power for magnification, the real world viewed through the partial reflector formed by the partially reflective coating is not distorted. Further, because the partial reflector is in the form of a coating, it is extremely thin and as such does not produce ghost images. The image of the displayed information may thus be readily seen without interference. Even though the partial reflector of the present invention is extremely thin, because it is formed on a solid body optical element, it has structural integrity.

In a preferred embodiment, the partially reflective coating is contained within the body of the optical element between a first prism portion and a second prism portion so that it cannot be touched or scratched. Thus, the optical element of the present invention is extremely rugged. These and other advantages and novel features of the present invention, as well as details of an illustrated embodiment thereof, will be more fully understood from the following description and drawings. BRIEF DESCRIPTION OF THE DRAWING

Fig. 1 is a perspective view of a head mounted display system in accordance with the present invention; Fig. 2 is a side view of a user wearing the head mounted display system of Fig. l to view an image of displayed information at a distance from the user and that appears to be superimposed on the real world; Fig. 3 is an exploded view of the solid optical element and display components for the head mounted display system of Fig. 1;

Fig. 4 is a front cross-sectional view of the head mounted display system of Fig. l illustrating an adjustable display assembly;

Fig. 5 is an illustration of a second embodiment of the display assembly with an optical element as shown in Fig. 3.;

Fig. 6 is a cross-sectional view of a second embodiment of a solid block optical element and a zoom display assembly;

Fig. 7 is a perspective view of a polarizer to be positioned on the support of the head mounted display system in front of the user's eye that does not view the displayed information;

Fig. 8 is a top view of one embodiment of the optical element of Fig. 1; and

Fig. 9 is a bottom view of the head mounted display system with integral microphone.

DESCRIPTION OF THE PREFERRED EMBODIMENT

A head mounted display system 10 as shown in Figs. 1-4 includes a frame 12 for supporting a display 14 and solid block optical element 16 so that the user can view an enlarged image 17 of information depicted on the display. The enlarged image 17 is projected by the optical element 16 so as to appear to be located at a distance d from the user that may be infinity or less than infinity depending upon the application for which the system 10 is worn. Further, as discussed in detail below, the optical element 16 is at least semi-transparent so that the projected image 17 appears to be superimposed on the real world, a portion of which is viewed by the user through the optical element 16.

The frame 12 includes a central support 18 on which the optical element 16 and display 14 are mounted so that the optical element 16 is in the direct line of sight 20 of one of the user's eyes. The central support 18 is coupled to a headband 22 by a pair of arms 24 and 26. The headband 22 includes a contoured front portion 28 made of a material such as plastic that has the structural integrity to support the arms 24, 26, central support 18, display 14 and optical element 16. A foam pad 30 or the like is disposed on an inner surface of the front portion 28 of the headband 22 so as to provide a cushion between the user's head and the front portion 28 of the headband 22. The headband 22 also includes an adjustable strap 32 that may be made of fabric, plastic or the like so as to secure the frame 12 about a user's head.

The central support 18 and thus the optical element 16 may be moved towards the user's face or away therefrom by the adjustable coupling of the arms 24 and 26 to the central support 18. More particularly, mounted on an outer end of each of the arms 24, 26, is a locking interface member 42. The locking interface member 42 on the arm 24 engages a portion of a locking member 34 that extends through a slot 38 in the central support 18. Similarly, a locking interface member on the arm 26 engages a portion of a locking member 36 that extends through a slot 40 formed on a side of the central support opposite the side of the slot 38. As the locking members 34, 36 are moved in the slots 38, 40 in a forward direction towards the front 41 of the central support 18, the central support 18 is moved closer to the face of the user. When the locking members 34, 36 are slid back in the slots 38, 40 towards the user, the central support 18 is moved away from the face of the user. This adjustable mounting for the central support 18 and thus the optical element 16 allows the optical element 16 to be adjustably positioned so as to accommodate different users. It is noted that the arms 24 and 26 may be pivotally attached to the headband 22 by adjustable clamping members 46 and 48 so that the central support 18 can be raised and lowered. Further, a housing 50 for the electronics of the head mounted display system may be disposed adjacent one of the clamping members 48 on a side of the frame 12 that is opposite to the location of the display 14 and optical element 16 so as to act as a counterweight thereto.

The optical element 16 as shown in detail in the exploded perspective view of Fig. 3 has a solid body formed of a first prism 52 and second prism 54. A lower surface 56 of the upper prism portion 52 is cut at a 45° angle with respect to a face 58 of the display 14. An upper surface 60 of the lower prism portion 54 of the optical element 16 has a 45° angle cut that is complimentary to the 45° angle cut of the upper prism portion 52 to allow the surfaces 56 and 60 to abut each other to form an optical element 16 having a solid body. A partially reflective coating 60 is formed on either the upper surface 60 of the lower prism 54 as shown in Fig. 3 or on the lower surface 56 of the upper prism portion 52 so as to form an internal partial reflector when the upper prism 52 is attached to the lower prism 54. The lower prism portion 54 has a focusing surface 62 that has a spherical shape to magnify the information depicted on the display 14. The focusing surface 62 has a central axis 64 that extends through a vertex of the surface 62 wherein the central axis 64 is coaxial with a central axis of the display 14, the central axis of the display 14 being perpendicular to the face 58 of the display 14. The central axis 64 of the focusing surface 62 is also perpendicular to the direct line of sight or see through axis 20 of the optical element 16. The focusing surface 62 of the lower prism 54 is made fully reflective so as to reflect an image of the information depicted on the face 58 of the display 14 to the partial reflector 60 that in turn reflects the image to an eye of the user. The user perceives an enlarged image of the displayed information as projected by the focusing surface 62 at a distance from the user that is greater than the optical path from the display to the user's eye through the optical element 16. Because the internal coating 60 is partially reflective, the image perceived by the user appears to be superimposed upon the real world. Further, since the central axis 64 of the focusing surface 62 having magnification power is perpendicular to the visual axis 20 along which the user looks to perceive the image, the portion of the real world viewed by the user through the optical element 16 is not distorted. This is extremely important when the head mounted display system is worn by a user who has to function in the real world.

The solid body of the optical element 16 makes it extremely rugged. Further, because the reflector 60 is contained within the solid body of the optical element 16 so that it is internal therein, the reflective coating cannot be scratched and dirt cannot accumulate thereon. This also contributes to the ruggedness of the optical system of the present invention. In a preferred embodiment, the sides 66 and 68 of the optical element 16 are covered with a black material or coating that is extremely thin, as is the bottom of the focusing surface 62 of the optical element 16. The coating on the optical surface 62 protects the surface 62 so that it in effect is internal to the optical element 16. Further, the sides 66 and 68 of the optical element 16 seem to disappear when colored black so that they are not perceived by the user. The displayed information thus appears to be part of the real world. Further, by angling the black sides 66 and 68 outwardly on the order of 12°-18° as shown in Fig. 8, the sides 66 and 68 of the optical element 16 become even less noticable by the user. The reflective coating 60 is preferably within the range of 25% to 75% reflective whereas the focusing surface 62 of the optical element is made 100% reflective. The prisms 52 and 54 may be formed of a transparent material having an index of refraction of 1.00 to 1.78. One preferred material is polymethylmethacrylate (PMMA) having an index of 1.49.

In order to protect the optical element 16 in the event that the head mounted display system 10 is dropped, the lower surface 62 is covered as shown in Fig. 9 with a resilient shock absorbing material 65 such as rubber or the like so as to form a cushion or bumper on the bottom of the optical element 16. As discussed above, the bumper 65 is preferably black in color or coated with a black material so as to reduce the visual prominence thereof. It has been found that the solid body optical element 16 forms a rugged support for a microphone 67 that is employed to pick up voice commands from the user for controlling the information depicted on the display 14. The microphone 67 is preferably a noise cancellation microphone that is mounted on the bottom 65 of the optical element 16 adjacent an inner most corner 69 of the element 16 so that the microphone 67 is positioned in close proximity to the user's mouth. Wires 71 connecting the microphone 67 to electronics contained in the housing 70 and/or housing 50 are further preferably formed by deposition of a metal film on one of the black sides 68 of the optical element 16 and a portion of the bottom 65 of the optical element 16 so as to connect to the microphone 67. After the wires 71 are deposited on the side and bottom portion of the optical element 16 they are covered by an electrically insulating coating or material that is preferably black in color. The use of the optical element 16 as a mounting surface for the microphone 67 eliminates the need for a boom or the like to mount the microphone on the system 10. As a result, the head mounted display system 10 with integral optical element 16 and microphone 67 is extremely compact, rugged and cost effectively manufacturable.

The display 14 is adjustably mounted in a housing 70 disposed on an upper surface of the central support 18 to vary the distance between the face 58 of the display 14 with respect to the focusing surface 62 as shown in Fig. 4. Specifically, the peripheral edge of the display 14 is supported in a movable member 72 between a bottom flange 74 and an upper flange 76. Also supported in the movable member 72 is a backlight assembly 78. The display 14 may take the form of a liquid crystal display panel wherein the backlight 78 may take the form of a miniature fluorescent tube or the like. The movable member 72 is formed with a threaded aperture 80 therein for receiving a threaded screw 82 or the like, the head of which is attached to a focusing knob 84. The threaded screw extends through an elongated aperture 86 formed in the housing 70 wherein the knob 84 may be moved upwardly in the aperture 86 to slide the display 14 upward with respect to the optical element 16. Once the display 14 is in the correct position, the knob 84 is turned so as to tighten the knob against the wall 88 of the housing 70 to securely maintained the position of the display 14. Similarly, to move the display 14 downward towards the optical element 16, the knob 84 is first loosened and moved downwardly in the aperture 86 of the housing 70. After the display 14 is moved to the desired position, the knob 84 is again tightened against the wall 88 of the housing 70.

A second embodiment of the display assembly for use with the optical element 16 of the present invention is illustrated in the exploded view of Fig. 5. As shown therein, the liquid crystal display 14 is positioned adjacent an upper surface 90 of the upper prism 52. An illumination assembly 92 is disposed on top of the display 14 so as to be adjacent to the back thereof. The illumination assembly 92 includes a light emitting diode (LED) array 94 that forms a backlight for the display 14. Disposed between the LED array 94 and the liquid crystal display 14 is a Fresnel lens or light coUimator 96 that captures the light from the LED array 94 and focuses the light onto a light diffuser 98. The light diffuser 98 is disposed between the coUimator 96 and the display 14 wherein the light diffuser is employed to provide a diffuse light to the back of the liquid crystal display panel 14. The illumination assembly 92 is very low in power consumption and is also compact so as to be extremely suitable for a head mounted display system.

Fig. 6 illustrates a second embodiment of the optical element 16 that is similar to the embodiments depicted in Figs. 3 and 5; however, the upper surface 100 of the upper prism 52 is curved so as to form a lens surface of the optical element 16. A zoom system is provided by inserting a negative lens 102 between the optical element 16 and the display 14 wherein the negative lens 102 is movable vertically so as to vary the distance of the lens 102 between the display 14 and optical element 16.

It is noted that the coating 60 of the optical element 16 does not allow as much ambient light to reach the user's display viewing eye as the amount of ambient light that reaches the user's other eye. So as to balance the ambient light that reaches the user's non-display viewing eye with the ambient light reaching the user's display viewing eye, a polarizer 104 as shown in Fig. 4 may be mounted on the central support 18 in front of the user's non-display viewing eye. The polarizer 104 also functions to eliminate eye dominance problems that various users might experience. The polarizer 104 includes a first element 106 that is polarized horizontally for example. A second element 108 is also polarized horizontally but is adjustable with respect to the element 106 so as to change the angle of polarization thereof with respect to the polarization of the element 108. By adjusting the element 108 with respect to the element 106 of the polarizer 104 so that they are not aligned in polarization, the amount of ambient light reaching the user's non-display viewing eye can be reduced so as to be balanced with the ambient light reaching the user's display viewing eye or to eliminate eye-dominance problems.

It will be appreciated, that by mounting a second optical element 16 and display 14 on the central support 18 of the frame 12 so as to be positioned in front of the user's left eye, a binocular head mounted display system can be provided. Preferably, in a binocular system the display and optical element associated with one eye and the display and optical element associated with the user's other eye are disposed on the central support 18 at a convergence angle with respect to each other so that the enlarged image projected by the right eye optical element 16 coincides with the enlarged image projected by the left eye optical element 16. Many other modifications and variations of the present invention are possible in light of the above teachings. Thus, it is to be understood that, within the scope of the appended claims, the invention may be practiced otherwise than as described hereinabove.

What is claimed and desired to be secured by Letters Patent is:

Claims

1. A head mounted display system comprising: a support to mount the system on a user's head; a display mounted on said support for displaying information; an optical element having a solid body mounted on said support and having a partially reflective coating at an approximately 45° angle with respect to said display and through which a user looks to view an image of said displayed information and said solid optical element having a focusing surface shaped to magnify said image, said focusing surface being coaxial with said display.

2. A head mounted display system as recited in claim 1 wherein said partially reflective coating is contained within the body of said optical element.

3. A head mounted display system as recited in claim 1 wherein said partially reflective coating is disposed on a surface of said solid optical element.

4. A head mounted display system as recited in claim 1 wherein said partially reflective coating is disposed between said focusing surface and said display.

5. A head mounted display system as recited in claim 1 wherein said focusing surface is reflective.

6. A head mounted display system as recited in claim 1 wherein said display includes a liquid crystal display panel and a backlight that includes an array of light emitting diodes.

7. A head mounted display system as recited in claim 6 wherein said backlight includes a light coUimator and a light diffuser disposed between said light coUimator and a back of said liquid crystal display.

8. A head mounted display system as recited in claim 1 wherein the sides of said optical element are coated black.

9. A head mounted display system as recited in claim 1 further including a polarizer disposed on said support so as to be positioned in front of a user's non-display viewing eye, said polarizer being adjustable to vary the amount of light reaching the user's non-display viewing eye.

10. A head mounted display system as recited in claim 1 wherein said focusing surface is a fully reflective spherical surface.

11. A head mounted display system as recited in claim 1 wherein said solid body of said optical element is made of a transparent material having an index of refraction with a range of 1.00 to 1.78.

12. A head mounted display system comprising: a support to mount the system on a user•s hea ; a display mounted on said support for displaying information; an optical element having a solid body mounted on said support and having an internal partial reflector disposed at an approximately 45° angle with respect to said display and through which a user looks along a central visual axis to view an image of said displayed information and said solid optical element having a surface shaped to magnify said image, said focusing surface having a central axis extending through a vertex of said focusing surface, said central axis of said focusing surface being perpendicular to said central visual axis.

13. A head mounted display system as recited in claim 12 wherein said focusing surface is reflective.

14. A head mounted display system as recited in claim 12 wherein said partial reflector is formed as a coating on a portion of said solid body.

15. A head mounted display system as recited in claim 12 wherein said display includes a liquid crystal display panel and a backlight that includes an array of light emitting diodes.

16. A head mounted display system as recited in claim 15 wherein said backlight includes a light coUimator and a light diffuser disposed between said light coUimator and a back of said liquid crystal display.

17. A head mounted display system as recited in claim 12 wherein the sides of said optical element are coated black.

18. A head mounted display system as recited in claim 12 further including a polarizer disposed on said support so as to be positioned in front of a user's non-display viewing eye, said polarizer being adjustable to vary the amount of light reaching the user's non-display viewing eye.

19. A head mounted display system as recited in claim 12 wherein said focusing surface is a fully reflective spherical surface.

20. A head mounted display system as recited in claim 12 wherein said solid body includes a first prism portion and a second prism portion on which said focusing surface is formed and said partial reflector abuts each of said first and second prism portions.

21. A head mounted display system comprising: a support to mount the system on a user's head; a display mounted on said support for displaying information; an optical element having a solid body mounted on said support with respect to said display, said optical element having a first prism having a lower surface cut at a 45° angle with respect to said display, a second prism having an upper surface cut at a 45° angle with respect to said display and a lower focusing surface shaped to magnify an image of said displayed information, and a partial reflector disposed between said first prism and said second prism wherein said partial reflector abuts the lower surface of said first prism and the upper surface of said second prism so as to be at a 45° angle with respect to said display.

22. A head mounted display system as recited in claim 21 wherein said first prism has an upper surface shaped so as to form a lens surface.

23. A head mounted display system as recited in claim 22 wherein said display is fixedly mounted on said support adjacent to said display.

24. A head mounted display system as recited in claim 21 wherein said display is movably mounted on said support with respect to said display.

25. A head mounted display system as recited in claim 21 wherein each of said first and second prisms are formed of an acrylic material.

26. A head mounted display system as recited in claim 21 wherein said acrylic material is polymethylmethacrylate.

27. A head mounted display system as recited in claim 21 wherein said partial reflector is formed as a partially reflective coating on the lower surface of said first prism.

28. A head mounted display system as recited in claim 21 wherein said partial reflector is formed as a partially reflective coating on the upper surface of said second prism.

29. A head mounted display system as recited in claim 21 wherein said focusing surface is a fully reflective spherical surface.

30. A head mounted display system as recited in claim 21 wherein the sides of said optical element are coated black.

31. A head mounted display system as recited in claim 21 wherein the sides of said optical element are coated black and angled outwardly.

32. A head mounted display system comprising: a support to mount the system on a user's head; a display mounted on said support for displaying information; an optical element having a solid body mounted on said support and having an internal partial reflector at an approximately 45° angle with respect to said display and through which a user looks to view an image of said displayed information; and a microphone mounted on a bottom of said optical element so as to pick up a user's voice.

33. A head mounted display system as recited in claim 32 wherein said optical element includes metal deposited on a side thereof for connection to said microphone.

34. A head mounted display system as recited in claim 33 wherein said metal is covered by a black electrically insulating material.

35. A head mounted display system as recited in claim 32 wherein said microphone is a noise cancellation microphone.