Head-mounted display with off-board illumination

• US 10,732,340 B2
• Filed: 07/21/2017
• Issued: 08/04/2020
• Est. Priority Date: 07/21/2016
• Status: Active Grant

• Current Assignee: Google LLC (Alphabet Inc.)
• Original Assignee: Google LLC (Alphabet Inc.)
• Inventors: Schubert, Martin Friedrich, Grundmann, Michael
• Primary Examiner(s): Macchiarolo, Leah Simone
• Application Number:
  US15/656,589
• Publication Number:
  US 20180024286A1
• Time in Patent Office: 1,110 Days
• CPC Class Codes: G02B 27/0172 characterised by optical features
• CPC Class Codes: G02B 6/0006 Coupling light into the fibre in general G02B6/4298
• CPC Class Codes: G02B 6/0008 the light being emitted at the end of the fibre
• CPC Class Codes: G02B 6/0028 Light guide, e.g. taper
• CPC Class Codes: G02B 6/005 provided by one optical element, or plurality thereof, placed on the light output side of the light guide
• CPC Class Codes: G02B 6/0068 Arrangements of plural sources, e.g. multi-colour light sources
• CPC Class Codes: G02B 6/0075 Arrangements of multiple light guides G02B6/0028 takes precedence

Abstract

Techniques of providing illumination to a head-mounted display (HMD) involve providing off-board illumination apart from the HMD. An off-board illumination unit delivers the illumination to the HMD via optical fibers. The optical fibers are lightweight and do not restrict motion of a user. Because the power source is less restricted, the off-board illumination unit provides flexibility in the hardware used to generate the illumination. For example, the illumination unit may use red, green, and blue narrow-band diode lasers. Further, by controlling modes in the fiber and providing additional light-guiding hardware, the angles at which light strikes LCD pixels may be largely restricted to certain specified angles. Restricted angles of incidence enable the use of fast-switching liquid crystals without degrading the image quality. Such a restriction allows for high-resolution imaging using rapid switching of the liquid crystal which enables very low latencies.

Claims

1. A system, comprising:

a head-mounted display, HMD;

an external light source separate from the HMD, the external light source including a red light source configured to generate red light, a green light source configured to generate green light, and a blue light source configured to generate blue light, the green light source being disposed between the red light source and the blue light source so that the external light source is configured to produce the red light, the green light, and the blue light in a sequential order; and

at least one optical fiber disposed between the external light source and the HMD, the at least one optical fiber being configured to deliver light generated by the external light source to the HMD via a lightguide to provide illumination for the HMD and including a first optical fiber configured to deliver red light from the red light source to the HMD, a second optical fiber configured to deliver green light from the green light source to the HMD, and a third optical fiber configured to deliver blue light from the blue light source to the HMD.

2. The system as in claim 1, wherein the HMD includes a display that includes a set of spatial light modulators, SLMs.

3. The system as in claim 2, wherein an SLM of the set of SLMs includes a liquid crystal display, LCD.

4. The system as in claim 3, wherein the LCD includes LCD pixels, each LCD pixel including a twisted nematic liquid crystal.

5. The system as in claim 2, wherein an SLM of the set of SLMs includes a microelectromechanical system, MEMS, grating light valve.

6. The system as in claim 1, wherein the at least one optical fiber configured to deliver the light is further configured and arranged to output the light to the lightguide in a specified polarization state.

7. The system as in claim 1, wherein the light source includes a set of diode lasers.

8. The system as in claim 1, wherein the light guide includes an achromatic metasurface configured to direct the red light, the green light, and the blue light to substantially the same location within the HMD.

9. The system as in claim 1, wherein the lightguide directs the light delivered by the at least one optical fiber using a diffraction grating.

10. The system as in claim 9, wherein the diffraction grating is configured to scatter substantially all of the light coupled into the lightguide into a specified set of propagation angles.

11. The system as in claim 1, further comprising, for each of the at least one optical fiber, a respective optical system configured to send the light delivered by that optical fiber into a respective plurality of lightguides.

12. The system as in claim 1, wherein the external light source is included in a base unit, the base unit being configured to generate images for display on the HMD.

13. A method, comprising:

generating red light, green light, and blue light by an external light source; and

transmitting the generated light to a head-mounted display, HMD, separate from the external light source via at least one fiber optic, the at least one optical fiber being configured to deliver the light generated by the external light source to the HMD via a lightguide to provide illumination for the HMD and including a first optical fiber configured to deliver red light from the external light source to the HMD, a second optical fiber configured to deliver green light from the external light source to the HMD, and a third optical fiber configured to deliver blue light from the external light source to the HMD, the lightguide includes a grating structure on an exit surface of the lightguide, the grating structure configured to direct the light having a first wavelength with a first propagation angle and a second wavelength with a second propagation angle.

14. The method as in claim 13, wherein transmitting the generated light to the HMD includes outputting the light to the lightguide in a specified polarization state.

15. The method as in claim 13, wherein the first wavelength with the first propagation angle light is directed toward a display of the HMD and the second wavelength with the second propagation angle light is directed away from the display of the HMD.

16. The method of claim 13, wherein the first wavelength with the first propagation angle light is red light and the second wavelength with the second propagation angle light is blue light.

17. A system, comprising:

a head-mounted display, HMD;

an external light source separate from the HMD, the external light source including a red light source configured to generate red light, a green light source configured to generate green light, and a blue light source configured to generate blue light;

at least one optical fiber disposed between the external light source and the HMD, the at least one optical fiber being configured to deliver light generated by the external light source to the HMD, the at least one optical fiber including a first optical fiber configured to deliver red light from the red light source to the HMD, a second optical fiber configured to deliver green light from the green light source to the HMD, and a third optical fiber configured to deliver blue light from the blue light source to the HMD; and

a lightguide configured to provide illumination for the HMD, the lightguide including a grating structure configured to deliver the light having a first wavelength with a first propagation angle toward a display of the HMD and a second wavelength with a second propagation angle away from the display of the HMD.

18. The method of claim 17, wherein the first wavelength with the first propagation angle light is delivered by the first optical fiber and the second wavelength with the second propagation angle light is delivered by the third optical fiber.