HIGH-RESOLUTION FREEFORM EYEPIECE DESIGN WITH A LARGE EXIT PUPIL

• US 20180045949A1
• Filed: 08/11/2017
• Published: 02/15/2018
• Est. Priority Date: 08/12/2016
• Status: Active Grant

• Current Assignee: Arizona Board of Regents (University of Arizona)
• Original Assignee: Arizona Board of Regents (University of Arizona)
• Inventors: Hua, Hong, Kuhn, Jason W
• Granted Patent: US 10,739,578 B2
• Time in Patent Office: Days
• CPC Class Codes: G02B 17/0856 comprising a refractive element with a reflective surface, the reflection taking place inside the element, e.g. Mangin mirrors
• CPC Class Codes: G02B 2027/0123 comprising devices increasing the field of view
• CPC Class Codes: G02B 2027/014 comprising information/image processing systems
• CPC Class Codes: G02B 25/001 Eyepieces
• CPC Class Codes: G02B 27/0081 with means for altering, e.g. enlarging, the entrance or exit pupil
• CPC Class Codes: G02B 27/0172 characterised by optical features
• CPC Class Codes: G02B 5/04 Prisms

Abstract

Near-to-eye systems and head-mounted displays and more particularly but not exclusively to an optimized freeform wedge-shaped prism design having free-form surfaces efficiently mathematically represented and configured to provide both high resolution and a large exit pupil heretofore unachieved.

Claims

1. A free-form prism-lens constructed of a material with refractive index greater than 1 for use in a near-to-eye display system comprising:

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

b. 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 reflect the received light at the second surface; and

c. a third free-form surface configured to receive the light reflected by the second free-form surface and to at least partially reflect the light back towards the second free-form surface and then out of the prism-lens,

wherein the reflection at the second free-form surface and the at least partial reflection at the third free-form surface occurs within a selected folding plane, and wherein the prism-lens has a field-of view in the folding plane greater than the field-of view in a plane perpendicular to the folding plane.

2. The free-form prism-lens of claim 1, wherein said prism-lens has a center-field effective F/# of less than 3.5 and an exit pupil diameter of at least 8 mm;

3. The free-form prism-lens of claim 1, wherein at least one of the three free-form surfaces of the free-form prism-lens is described by an axially asymmetric quadratic and a set of orthogonal polynomials:

4. The free-form prism-lens of claim 1, wherein the third free-form surface is coated with a reflective coating to reflect all light from the second free-form surface back towards the second free-form surface and then to exit the free-form prism-lens.

5. The free-form prism-lens of claim 1, wherein the third free-form surface, in addition to reflecting light from the second free-form surface back towards the second free-form surface and then to exit the free-form prism-lens also admits light from outside the free-form prism from real-world scenes to also be transmitted towards the second free-form surface and then to exit the free-form prism-lens.

6. The free-form prism-lens of claim 1, comprising an auxiliary lens disposed proximate to 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 free-form surfaces.

7. The free-form prism-lens of claim 6 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.

8. The free-form prism-lens of claim 1, wherein the eye-clearance is at least 18 mm.

9. The free-form in prism-lens of claim 1, wherein the field-of view of the prism-lens in the folding plane is at least 28 degrees.

10. The free-form prism-lens of claim 1, wherein the field-of view of the prism-lens in the plane perpendicular to the folding plane is at least 21 degrees

11. The free-form prism-lens of claim 1, wherein the spatial distortion at maximum field angle is less than 10%.

12. The free-form prism-lens of claim 1, wherein the effective focal length is less than 20 mm.

13. The free-form prism-lens of claim 1, wherein the vignetting at the maximum field positions is less than 40%.

14. The free-form prism-lens of claim 1, wherein the microdisplay has a pixel pitch of 7.5 microns or larger.

15. The free-form prism-lens of claim 1, wherein the modulation transfer function across the entire field of view is greater than 30% at the spatial frequency of 33 line-pairs/mm and greater than 10% at the spatial frequency of 50 line-pairs/mm.

16. The free-form prism lens of claim 1, wherein the prism-lens is formed through an injection-moulding process.

17. The free-form prism-lens of claim 1, wherein the prism-lens is composed of either poly methyl methacrylate or a cyclic olefin polymer.

18. The free-form prism-lens of claim 1, wherein the reflection of light by the second free-form surface towards the third free-form surface is achieved without the application of any reflective coating to the second free-form surface.

19. The free-form prism-lens of claim 1, wherein the second free-form surface is configured to both perform reflection of light incident from the first free-form surface as well as perform refraction of light incident from the third free-form surface.