LIGHTWEIGHT EYEPIECE FOR HEAD MOUNTED DISPLAY

• US 20130070338A1
• Filed: 09/21/2011
• Published: 03/21/2013
• Est. Priority Date: 09/21/2011
• Status: Active Grant

• Current Assignee: Google LLC (Alphabet Inc.)
• Original Assignee: Google Inc. (Alphabet Inc.)
• Inventors: Gupta, Anurag, Amirparviz, Babak, Sharma, Sumit
• Granted Patent: US 9,013,793 B2
• Time in Patent Office: Days
• US Class Current: 359/485.05
• CPC Class Codes: G02B 27/0172 characterised by optical features
• CPC Class Codes: G02B 5/30 Polarising elements light-modulating devices with active elements G02F1/00
• CPC Class Codes: G02B 6/0035 provided on the surface of the light guide or in the bulk of it

Abstract

An eyepiece includes an eyepiece frame, an in-coupling polarization beam splitter (“PBS”), an end reflector, and an out-coupling PBS. The eyepiece frame defines an air cavity and includes an illumination region for receiving computer generated image (“CGI”) light into the eyepiece frame and a viewing region to be aligned with an eye of a user. The in-coupling PBS is supported within the eyepiece frame at the illumination region to re-direct the CGI light to a forward propagation path extending along the air cavity towards the viewing region. The end reflector is disposed to reflect the CGI light back along a reverse propagation path within the eyepiece frame. The out-coupling PBS is supported at the viewing region to pass the CGI light traveling along the forward propagation path and to redirect the CGI light traveling along the reverse propagation path out of an eye-ward side of the eyepiece frame.

Claims

1. An eyepiece for a head mounted display, the eyepiece comprising:

an eyepiece frame defining an air cavity, the eyepiece frame including an illumination region for receiving computer generated image (“

CGI”

) light into the eyepiece frame and a viewing region to be aligned with an eye of a user;

in-coupling polarization beam splitter (“

PBS”

) supported within the eyepiece frame at the illumination region to re-direct the CGI light to a forward propagation path extending along the air cavity towards the viewing region;

a reflector disposed at an opposite end of the eyepiece frame from the illumination region to reflect the CGI light back along a reverse propagation path within the eyepiece frame;

out-coupling PBS supported within the eyepiece frame at the viewing region to pass the CGI light traveling along the forward propagation path and to redirect the CGI light traveling along the reverse propagation path out of an eye-ward side of the eyepiece frame; and

a polarization rotator disposed in the forward and reverse propagation paths of the CGI light between the out-coupling PBS and the reflector.

2. The eyepiece of claim 1, wherein the out-coupling PBS reflects a substantially orthogonal polarization component of the CGI light than the in-coupling PBS reflects.

3. The eyepiece of claim 1, wherein the eyepiece frame comprises a metal frame including:

elongated members that extend from the illumination region to the viewing region and run substantially parallel to the forward propagation path; and

cross members that rigidly hold the elongated members together.

4. The eyepiece of claim 3, wherein the metal frame comprises a magnesium metal frame.

5. The eyepiece of claim 3, further comprising:

substantially transparent side sheets mounted to the metal frame to protect components internal to the metal frame, wherein the eyepiece passes ambient scene light through an ambient scene side and the eye-ward side of the eyepiece in the viewing region to augment the ambient scene light with the CGI light.

6. The eyepiece of claim 5, wherein the substantially transparent side sheets comprises sheets of Zeonex.

7. The eyepiece of claim 1, wherein the in-coupling PBS comprises a first wire grid polarizer.

8. The eyepiece of claim 7, wherein the out-coupling PBS comprises a second wire grid polarizer, wherein wire lines of the second wire grid polarizer are orientated to run substantially orthogonal to wire lines of the first wire grid polarizer.

9. The eyepiece of claim 7, wherein the out-coupling PBS comprises a thin film polarizer that reflects a substantially orthogonal polarization component of the CGI light than the first wire grid polarizer reflects.

10. The eyepiece of claim 1, further comprising:

an illumination module disposed at the illumination region; and

a reflective display panel disposed at the illumination region for generating the CGI light in response to illumination by the illumination module,

wherein the reflective display panel is disposed on an opposite side of the eyepiece from the illumination module in the illumination region with the in-coupling PBS disposed between the illumination module and the reflective display panel.

11. The eyepiece of claim 10, wherein the illumination module comprises:

a transparent expansion volume;

a light emitting diode mounted to a side of the transparent expansion volume to illuminate the transparent expansion volume with lamp light;

a first bright enhancement film (“

BEF”

) disposed adjacent to the transparent expansion volume to reduce divergence of the lamp light along a first axis;

a second BEF disposed adjacent to the first BEF to reduce the divergence of the lamp light along a second axis; and

a polarizer disposed between the second BEF and the in-coupling PBS.

12. The eyepiece of claim 1, wherein the reflector comprises a concave mirror coated onto a surface of a convex lens.

13. The eyepiece of claim 12, wherein the concave minor comprises a toroidal minor having multiple radiuses of curvatures.

14. A head mounted display (“

HMD”

) for displaying computer generated image (“

CGI”

) light to an eye of a user, the HMD comprising;

an eyepiece including;

an eyepiece frame defining an air cavity, the eyepiece frame including an illumination region for receiving computer generated image (“

CGI”

) light into the eyepiece frame and a viewing region to be aligned with an eye of a user;

an image source mounted to the eyepiece frame at the illumination region for generating the CGI light;

in-coupling polarization beam splitter (“

PBS”

) supported within the eyepiece frame at the illumination region to re-direct the CGI light received from the image source to a forward propagation path extending along the air cavity towards the viewing region;

an end reflector disposed at an opposite end of the eyepiece frame from the illumination region to reflect the CGI light back along a reverse propagation path within the eyepiece frame; and

out-coupling PBS supported within the eyepiece frame at the viewing region to pass the CGI light traveling along the forward propagation path and to redirect the CGI light traveling along the reverse propagation path out of an eye-ward side of the eyepiece frame; and

a frame assembly to support the eyepiece for wearing on a head of the user with the viewing region positioned in front of the eye of the user.

15. The HMD of claim 14, wherein the HMD comprises a binocular HMD including another eyepiece supported by the frame assembly in front of another eye of the user.

16. The HMD of claim 14, wherein the eyepiece further includes:

a polarization rotator disposed in the forward and reverse propagation paths of the CGI light between the out-coupling PBS and the end reflector.

17. The HMD of claim 14, wherein the out-coupling PBS reflects a substantially orthogonal polarization component of the CGI light than the in-coupling PBS reflects.

18. The HMD of claim 14, wherein the eyepiece frame comprises a metal frame including:

elongated members that extend from the illumination region to the viewing region and run substantially parallel to the forward propagation path; and

cross-members that rigidly hold the elongated members together.

19. The HMD of claim 18, wherein the eyepiece further comprises:

substantially transparent side sheets mounted to the metal frame to protect components internal to the metal frame, wherein the eyepiece passes ambient scene light through an ambient scene side and the eye-ward side of the eyepiece in the viewing region to augment the ambient scene light with the CGI light.

20. The HMD of claim 14, wherein the in-coupling PBS comprises a first wire grid polarizer.

21. The HMD of claim 20, wherein the out-coupling PBS comprises a second wire grid polarizer, wherein wire lines of the second wire grid polarizer are orientated to run substantially orthogonal to wire lines of the first wire grid polarizer.

22. The HMD of claim 20, wherein the out-coupling PBS comprises a thin film polarizer that reflects a substantially orthogonal polarization component of the CGI light than the first wire grid polarizer reflects.

23. The HMD of claim 14, wherein the image source comprises:

an illumination module; and

a reflective display panel for generating the CGI light in response to illumination by the illumination module,

wherein the reflective display panel is disposed on an opposite side of the eyepiece from the illumination module in the illumination region with the in-coupling PBS disposed between the illumination module and the reflective display panel.

24. An eyepiece for a head mounted display, the eyepiece comprising:

an eyepiece frame including an illumination region for receiving computer generated image (“

CGI”

) light into the eyepiece frame and a viewing region to be aligned with an eye of a user;

in-coupling polarization beam splitter (“

PBS”

) supported within the eyepiece frame at the illumination region to re-direct the CGI light to a forward propagation path extending towards the viewing region;

an end reflector disposed at an opposite end of the eyepiece frame from the illumination region to reflect the CGI light back along a reverse propagation path within the eyepiece frame; and

out-coupling PBS supported within the eyepiece frame at the viewing region to pass the CGI light traveling along the forward propagation path and to redirect the CGI light traveling along the reverse propagation path out of an eye-ward side of the eyepiece frame,

wherein the out-coupling PBS reflects a substantially orthogonal polarization component of the CGI light than the in-coupling PBS reflects.

25. The eyepiece of claim 24, further comprising:

a polarization rotator disposed in the forward and reverse propagation paths of the CGI light between the out-coupling PBS and the end reflector.

26. The eyepiece of claim 24, wherein the eyepiece frame defines an air cavity and the forward propagation path extends along within the air cavity.

27. The eyepiece of claim 24, wherein the eyepiece frame comprises a metal frame including:

elongated members that extend from the illumination region to the viewing region and run substantially parallel to the forward propagation path; and

cross members that rigidly hold the elongated members together.

28. The eyepiece of claim 24, wherein the in-coupling PBS comprises a first wire grid polarizer and the out-coupling PBS comprises a second wire grid polarizer, wherein wire lines of the second wire grid polarizer are orientated to run substantially orthogonal to wire lines of the first wire grid polarizer.