LIGHT BEAM EXPANDING DEVICE, IMAGE DISPLAY DEVICE, AND OPTICAL DEVICE

• US 20130128611A1
• Filed: 11/15/2012
• Published: 05/23/2013
• Est. Priority Date: 11/22/2011
• Status: Active Grant

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Akutsu, Katsuyuki, Kuribara, Nobuaki, Imamura, Teppei
• Granted Patent: US 9,164,221 B2
• Time in Patent Office: Days
• US Class Current: 362/607
• CPC Class Codes: G02B 2027/011 comprising device for correcting geometrical aberrations, distortion
• CPC Class Codes: G02B 2027/0174 holographic
• CPC Class Codes: G02B 27/0172 characterised by optical features
• CPC Class Codes: G02B 27/1086 operating by diffraction only
• CPC Class Codes: G02B 27/14 operating by reflection only
• CPC Class Codes: G02B 27/4216 correcting geometrical aberrations
• CPC Class Codes: G02B 5/09 Multifaceted or polygonal mirrors , e.g. polygonal scanning mirrors; Fresnel mirrors
• CPC Class Codes: G02B 5/1842 Gratings for image generation G02B5/1847 takes precedence
• CPC Class Codes: G02B 6/0015 provided on the surface of the light guide or in the bulk of it
• CPC Class Codes: G02B 6/0031 Reflecting element, sheet or layer
• CPC Class Codes: G02B 6/0035 provided on the surface of the light guide or in the bulk of it
• CPC Class Codes: G02B 6/0055 Reflecting element, sheet or layer
• CPC Class Codes: G03H 1/0248 Volume holograms

Abstract

An image display device includes an image generating device, a light guide unit, and a light beam expanding device. The light guide unit includes a light guide plate, a first deflector, and a second deflector. The light beam expanding device expands a light beam incident from the image generating device along the Z direction and outputs the light beam to the light guide unit when the incident direction of light incident on the light guide plate is defined as the X direction and the propagation direction of light in the light guide plate is defined as the Y direction. The light beam expanding device is composed of a first reflective mirror on which light from the image generating device is incident and a second reflective mirror on which light from the first reflective mirror is incident and that outputs light to the light guide unit.

Claims

1. An image display device comprising:

an image generating device;

a light guide unit on which light from the image generating device is incident, the light guide unit guiding light and outputting light toward a pupil of a viewer, the light guide unit including

a light guide plate from which incident light is output after being propagated inside by total reflection,

a first deflector that is disposed in or on the light guide plate and deflects light incident on the light guide plate in such a manner that the light incident on the light guide plate is totally reflected inside the light guide plate, and

a second deflector that is disposed in or on the light guide plate and deflects light propagated inside the light guide plate by total reflection a plurality of times in order to output the light propagated inside the light guide plate by total reflection from the light guide plate; and

a light beam expanding device configured to expand a light beam incident from the image generating device along a Z direction and output the light beam to the light guide unit when incident direction of light incident on the light guide plate is defined as an X direction and propagation direction of light in the light guide plate is defined as a Y direction, wherein

the light beam expanding device is composed of a first reflective mirror on which light from the image generating device is incident and a second reflective mirror on which light from the first reflective mirror is incident and that outputs light to the light guide unit,

a light reflective surface of the first reflective mirror is composed of 1A-th inclined surfaces and 1B-th inclined surfaces that are juxtaposed alternately and continuously and has a saw-tooth shape as a sectional shape,

a light reflective surface of the second reflective mirror is composed of 2A-th inclined surfaces and 2B-th inclined surfaces that are juxtaposed alternately and continuously and has a saw-tooth shape as a sectional shape,

a top side and a bottom side of the 1A-th inclined surface are parallel to each other and extend along the Z direction,

an angle formed by a bottom part of the 1A-th inclined surface and a bottom part of the 1B-th inclined surface is 90 degrees,

a top side and a bottom side of the 2A-th inclined surface are parallel to each other and extend along the Y direction, and

an angle formed by a bottom part of the 2A-th inclined surface and a bottom part of the 2B-th inclined surface is 90 degrees.

2. The image display device according to claim 1, wherein

at least one planar reflective member is provided between the image generating device and the first reflective mirror,

at least one planar reflective member is provided between the first reflective mirror and the second reflective mirror, and

one planar reflective member provided between the image generating device and the first reflective mirror serves also as one planar reflective member provided between the first reflective mirror and the second reflective mirror.

3. The image display device according to claim 1, wherein

a trajectory of light incident on the first reflective mirror from the image generating device and a trajectory of light output from the first reflective mirror are parallel to each other when being projected onto a 1A-th virtual plane that is a virtual plane perpendicular to the Z direction,

the trajectory of the light incident on the first reflective mirror from the image generating device and the trajectory of the light output from the first reflective mirror are symmetric with each other about the 1A-th virtual plane when being projected onto a 1B-th virtual plane that is a virtual plane perpendicular to a normal to the first reflective mirror,

a trajectory of light incident on the second reflective mirror from the first reflective mirror and a trajectory of light output from the second reflective mirror are parallel to each other when being projected onto a 2A-th virtual plane that is a virtual plane perpendicular to the Y direction, and

the trajectory of the light incident on the second reflective mirror from the first reflective mirror and the trajectory of the light output from the second reflective mirror are symmetric with each other about the 2A-th virtual plane when being projected onto a 2B-th virtual plane that is a virtual plane perpendicular to a normal to the second reflective mirror.

4. The image display device according to claim 3, wherein optical path length of light that is output from the center of the image generating device and is incident on the first reflective mirror is equal to optical path length of light that is light originally output from the center of the image generating device and is output from the first reflective mirror and is incident on the second reflective mirror to be output from the second reflective mirror and be incident on the light guide unit.

5. The image display device according to claim 4, wherein size, along the Y direction, of a light beam output from the image generating device is equal to size, along the Y direction, of a light beam incident on the light guide unit.

6. The image display device according to claim 3, wherein size, along the Z direction, of a light beam incident on the light guide unit is larger than size, along the Z direction, of a light beam output from the image generating device.

7. The image display device according to claim 6, wherein size, along the Z direction, of a light beam output from the light guide unit is equal to size, along the Z direction, of the light beam output from the image generating device.

8. The image display device according to claim 1, wherein

the image generating device includes

an image forming device having a plurality of pixels arranged in a two-dimensional matrix manner, and

a collimating optical system that turns light output from the pixels of the image forming device to collimated light, and

light from the collimating optical system is incident on the first reflective mirror.

9. The image display device according to claim 1, wherein

the image generating device includes

a light source,

a collimating optical system that turns light output from the light source to collimated light,

a scanning unit that scans collimated light output from the collimating optical system, and

a relay optical system that relays collimated light scanned by the scanning unit, and

light from the relay optical system is incident on the first reflective mirror.

10. The image display device according to claim 1, wherein the first deflector and the second deflector are formed of diffraction grating elements.

11. The image display device according to claim 10, wherein the diffraction grating elements are formed of reflective diffraction grating elements.

12. The image display device according to claim 11, wherein the reflective diffraction grating elements are formed of reflective volume hologram diffraction gratings.

13. The image display device according to claim 10, wherein the diffraction grating elements are formed of transmissive diffraction grating elements.

14. The image display device according to claim 10, wherein one of the diffraction grating elements is formed of a reflective diffraction grating element and the other of the diffraction grating elements is formed of a transmissive diffraction grating element.

15. The image display device according to claim 1, wherein

the first deflector functions as a reflective mirror, and

the second deflector functions as a semi-transmissive mirror.

16. An optical device comprising:

a light guide unit configured to include

a light guide plate from which light incident from a light source is output after being propagated inside by total reflection,

a first deflector that is disposed in or on the light guide plate and deflects light incident on the light guide plate in such a manner that the light incident on the light guide plate is totally reflected inside the light guide plate, and

a second deflector that is disposed in or on the light guide plate and deflects light propagated inside the light guide plate by total reflection a plurality of times in order to output the light propagated inside the light guide plate by total reflection from the light guide plate; and

a light beam expanding device configured to expand a light beam incident from the light source along a Z direction and output the light beam to the light guide unit when incident direction of light incident on the light guide plate is defined as an X direction and propagation direction of light in the light guide plate is defined as a Y direction, wherein

the light beam expanding device is composed of a first reflective mirror on which light from the light source is incident and a second reflective mirror on which light from the first reflective mirror is incident and that outputs light to the light guide unit,

a light reflective surface of the first reflective mirror is composed of 1A-th inclined surfaces and 1B-th inclined surfaces that are juxtaposed alternately and continuously and has a saw-tooth shape as a sectional shape,

a light reflective surface of the second reflective mirror is composed of 2A-th inclined surfaces and 2B-th inclined surfaces that are juxtaposed alternately and continuously and has a saw-tooth shape as a sectional shape,

a top side and a bottom side of the 1A-th inclined surface are parallel to each other and extend along the Z direction,

an angle formed by a bottom part of the 1A-th inclined surface and a bottom part of the 1B-th inclined surface is 90 degrees,

a top side and a bottom side of the 2A-th inclined surface are parallel to each other and extend along the Y direction, and

an angle formed by a bottom part of the 2A-th inclined surface and a bottom part of the 2B-th inclined surface is 90 degrees.

17. The optical device according to claim 16, wherein

at least one planar reflective member is provided between the light source and the first reflective mirror,

at least one planar reflective member is provided between the first reflective mirror and the second reflective mirror, and

one planar reflective member provided between the light source and the first reflective mirror serves also as one planar reflective member provided between the first reflective mirror and the second reflective mirror.

18. A light beam expanding device comprising:

a first reflective mirror configured to be disposed between a light source and an irradiated surface, light from the light source being incident on the first reflective mirror; and

a second reflective mirror on which light from the first reflective mirror is incident, the second reflective mirror outputting light to the irradiated surface, wherein

a light reflective surface of the first reflective mirror is composed of 1A-th inclined surfaces and 1B-th inclined surfaces that are juxtaposed alternately and continuously and has a saw-tooth shape as a sectional shape,

a light reflective surface of the second reflective mirror is composed of 2A-th inclined surfaces and 2B-th inclined surfaces that are juxtaposed alternately and continuously and has a saw-tooth shape as a sectional shape,

a top side and a bottom side of the 1A-th inclined surface are parallel to each other and extend along the Z direction,

an angle formed by a bottom part of the 1A-th inclined surface and a bottom part of the 1B-th inclined surface is 90 degrees,

a top side and a bottom side of the 2A-th inclined surface are parallel to each other and extend along the Y direction, and

an angle formed by a bottom part of the 2A-th inclined surface and a bottom part of the 2B-th inclined surface is 90 degrees.

19. The light beam expanding device according to claim 18, wherein

at least one planar reflective member is provided between the light source and the first reflective mirror,

at least one planar reflective member is provided between the first reflective mirror and the second reflective mirror, and

one planar reflective member provided between the light source and the first reflective mirror serves also as one planar reflective member provided between the first reflective mirror and the second reflective mirror.

20. An image display device comprising:

an image generating device;

a light guide unit on which light from the image generating device is incident, the light guide unit guiding and outputting light; and

a first reflective mirror and a second reflective mirror, wherein

the first reflective mirror and the second reflective mirror are disposed on an optical path between the image generating device and the light guide unit and each have a saw-tooth shape.