Optical see-through free-form head-mounted display

• US 9,239,453 B2
• Filed: 08/27/2013
• Issued: 01/19/2016
• Est. Priority Date: 04/20/2009
• Status: Active Grant

• Current Assignee: Beijing Institute of Technology, Arizona Board of Regents (University of Arizona)
• Original Assignee: Beijing Institute of Technology, Arizona Board of Regents (University of Arizona)
• Inventors: Cheng, Dewen, Hua, Hong, Wang, Yongtian
• Primary Examiner(s): Sugarman, Scott J
• Assistant Examiner(s): Choudhury, Mustak
• Application Number:
  US14/010,956
• Publication Number:
  US 20140009845A1
• Time in Patent Office: 875 Days
• Field of Search: 359629-640, 359/720, 359/290, 359/260, 359/578, 356/454, 356/519, 385/14, 385/32
• US Class Current: 1/1
• CPC Class Codes: G02B 13/10 involving prisms G02B13/12 takes precedence
• CPC Class Codes: G02B 17/006 Systems in which light light is reflected on a plurality of parallel surfaces, e.g. louvre mirrors, total internal reflection [TIR] lenses Fresnel mirrors G02B5/09, Fresnel lenses G02B3/08
• CPC Class Codes: G02B 17/08 Catadioptric systems used in non-imaging applications G02B19/00
• CPC Class Codes: G02B 17/086 wherein the system is made of a single block of optical material, e.g. solid catadioptric systems
• CPC Class Codes: G02B 2027/0118 comprising devices for improving the contrast of the display / brillance control visibility
• CPC Class Codes: G02B 2027/013 comprising a combiner of particular shape, e.g. curvature
• CPC Class Codes: G02B 27/017 Head mounted
• CPC Class Codes: G02B 27/0172 characterised by optical features
• CPC Class Codes: G03B 21/00 Projectors or projection-type viewers; Accessories therefor devices for changing pictures G03B23/00

Abstract

A see-through free-form head-mounted display including a wedge-shaped prism-lens having free-form surfaces and low F-number is provided.

Claims

1. A free-form prism-lens for use in an optical see-through head-mounted display, comprising:

a first free-form surface configured to receive light from a micro-display and configured to transmit the received light into the body of the prism-lens;

a second free-form surface configured to receive the light transmitted into the body of the prism-lens from the first free-form surface and configured to totally internally reflect the received light at the second surface; and

a third free-form surface configured to receive the light reflected by the second free-form surface and configured to reflect the light out of the prism-lens,

wherein the prism-lens has an f-number less than 3.5 and an effective focal length of 21 mm or less, wherein the exit pupil diameter is at least 6 mm.

2. The free-form prism-lens according to claim 1, wherein the first free-form surface is described by

3. The free-form prism-lens according to claim 2, wherein the second free-form surface is described by

4. The free-form prism-lens according to claim 3, wherein the third free-form surface is described by

5. The free-form prism-lens according to claim 1, wherein at least one surface of the free-form prism-lens is described by

6. The free-form prism-lens according to claim 1, wherein the third free-form surface is partially mirrored to permit the internally reflected light to be reflected by the second free-form surface and to permit light from a real-world view to be transmitted through the third free-form surface to the exit pupil.

7. The free-form prism-lens according to claim 1, wherein second and third free-form surfaces are configured to provide a wedge-shaped prism lens.

8. The free-form prism-lens according to claim 1, wherein the z-axis is parallel to the optical axis at the exit pupil, and the prism lens is symmetric about the y-z plane and asymmetric about the x-z plane.

9. The free-form prism-lens according to claim 1, wherein the diagonal field of view is at least 40 degrees.

10. The free-form prism-lens according to claim 1, wherein the modulation transfer function is at least 10%×

30 lps/mm.

11. The free-form prism-lens according to claim 1, wherein the eye clearance is at least 16 mm.

12. The free-form prism-lens according to claim 1, comprising an auxiliary lens disposed proximate the third free-form surface, the auxiliary lens configured to minimize the shift and distortion of rays from a real-world scene by the second and third surfaces of the prism-lens.

13. The free-form prism-lens according to claim 12, wherein the auxiliary lens has a surface with the same shape as the third free-form surface of the prism-lens and is disposed in optical contact with the third free-form surface of the prism-lens.

14. The free-form prism-lens according to claim 13, wherein at least one surface of the auxiliary lens is described by

15. The free-form prism-lens according to claim 14, wherein the modulation transfer function is at least 10%×

30 lps/mm across the entire visual field.

16. The free-form prism-lens according to claim 12, wherein at least one surface of the auxiliary lens is described by

17. The free-form prism-lens according to claim 16, wherein the modulation transfer function is at least 10%×

30 lps/mm across the entire visual field.

18. The free-form prism-lens according to claim 1, wherein the prism-lens has an f-number less than 2.