ERGONOMIC HEAD MOUNTED DISPLAY DEVICE AND OPTICAL SYSTEM

• US 20140071539A1
• Filed: 09/11/2013
• Published: 03/13/2014
• Est. Priority Date: 09/11/2012
• Status: Active Grant

• Current Assignee: Magic Leap, Inc.
• Original Assignee: Magic Leap, Inc.
• Inventors: Gao, Chunyu
• Granted Patent: US 9,740,006 B2
• Time in Patent Office: Days
• US Class Current: 359/630
• CPC Class Codes: G02B 2027/011 comprising device for correcting geometrical aberrations, distortion
• CPC Class Codes: G02B 2027/0123 comprising devices increasing the field of view
• CPC Class Codes: G02B 27/0025 for optical correction, e.g. distorsion, aberration
• CPC Class Codes: G02B 27/0172 characterised by optical features

Abstract

Optical systems such as image display systems include a freeform optical waveguide prism and a freeform compensation lens spaced therefrom by a gap of air or index cement. The compensation lens corrects for aberrations which the optical waveguide prism will introduce in light or images from an ambient real-world environment. The optical waveguide prism receives actively projected images at an entry location, and emits the projected images at an exit location after internally reflecting the images along an optical path therein. The image display system may include an image source and coupling optics. The approach permits design of an optical viewing device, for example in optical see-through HMDs, achieving an eyeglass-form appearance and a wide see-through field of view (FOV).

Claims

1. An image display system comprising:

a freeform optical waveguide prism having a first major surface and a second major surface, the first major surface of the optical waveguide prism which in use is positioned to at least one of receive actively projected images into the optical waveguide prism from an active image source or emit the actively projected images out of the optical waveguide prism and the second major surface of the optical waveguide prism which in use is positioned to receive images of a real-world ambient environment into the optical waveguide prism, which real-world ambient environment is external to the image display system, at least some portions of the first and the second major surfaces of the optical waveguide prism being refractive surfaces that internally propagate light entering the optical waveguide prism along at least a portion of a length of the optical waveguide prism; and

a freeform compensation lens having a first major surface and a second major surface, the first major surface of the compensation lens having a shape that at least approximately matches a shape of the second major surface of the optical waveguide prism, the freeform compensation lens positioned relatively outwardly of the second major surface of the optical waveguide toward the real-world ambient environment to form a gap between the first major surface of the compensation lens and the second major surface of the optical waveguide prism.

2. The image display system of claim 1 wherein the refractive surfaces internally propagate light entering the optical waveguide prism at angles greater than a critical angle along at least the portion of the length of the optical waveguide prism via total internal reflection.

3. The image display system of claim 1 wherein at least a portion of at least one of the first or the second major surfaces of the optical waveguide prism bears a semi-transparent, partially reflective material.

4. The image display system of claim 1 wherein the optical waveguide prism has a peripheral edge extending between the first and the second major surfaces of the optical waveguide prism and which retains at least a portion of light within the optical waveguide prism.

5. The image display system of claim 1 wherein the gap between the first major surface of the compensation lens and the second major surface of the optical waveguide prism is a small gap.

6. The image display system of claim 1 wherein the gap between the first major surface of the compensation lens and the second major surface of the optical waveguide prism has a width that increases from at least proximate an entry location at which actively projected images enter into the optical waveguide prism to at least proximate an exit location at which the actively projected images exit the optical waveguide prism.

7. The image display system of claim 1 wherein the optical waveguide prism and the compensation lens focus images of the real-world ambient environment to a foci that is coincident with actively projected images which exit the optical waveguide prism via an exit location on the first major surface of the optical waveguide prism.

8. The image display system of claim 7 wherein the exit location on the first major surface of the optical waveguide prism is spaced along a length of the optical waveguide prism from an entry location on the first major surface of the optical waveguide prism at which actively projected images enter into the optical waveguide prism.

9. The image display system of claim 1 wherein the compensation lens compensates for ray shift and distortion of the images of the real-world ambient environment caused by the optical waveguide prism.

10. The image display system of claim 1 wherein rays of light forming the actively projected images cross and form an intermediate image inside the optical waveguide prism.

11. The image display system of claim 1, further comprising:

an image display unit positioned and oriented to provide images into the optical waveguide prism.

12. The image display system of claim 11, further comprising:

at least one coupling lens that guides light from the image display unit into the optical waveguide prism and corrects for optical aberrations.

13. The image display system of claim 11 wherein the image display unit is at least one of a self-emissive pixel array or an illuminated pixel array.

14. The image display system of claim 11 wherein the image display unit is selected from the group consisting of:

a liquid crystal on silicon (LCoS) display device, a liquid crystal display (LCD) panel, an organic light emitting display (OLED), ferroelectric liquid crystal on silicon (LCoS device, digital mirror device (DMD), and a micro-projector.

15. The image display system of claim 11, further comprising:

a matching cement received in the gap, securely coupling the compensating lens to the optical waveguide prism.

16. An image display system, comprising:

a freeform optical waveguide prism of a material having an index greater than one, a first major surface, a second major surface, and a peripheral edge that extends between a perimeter of the first major surface and a perimeter of the second major surface of the optical waveguide prism, the optical waveguide prism having an entry location on the first major surface of the optical waveguide prism at which actively projected images enter into the optical waveguide prism and an exit location on the first major surface of the optical waveguide prism at which the actively projected images exit the optical waveguide prism after a plurality of internal reflections along an optical path within the optical waveguide prism, the exit location is spaced along a length of the optical waveguide prism from the entry location.

17. The image display system of claim 16 wherein at least some portions of the first and the second major surfaces of the optical waveguide prism being refractive surfaces that internally propagate light entering the optical waveguide prism at angles greater than a critical angle along at least a portion of a length of the optical waveguide prism via total internal reflection.

18. The image display system of claim 16 wherein at least a portion of at least one of the first or the second major surfaces of the optical waveguide prism bears a semi-transparent, partially reflective material.

19. The image display system of claim 16 wherein the first major surface of the optical waveguide prism is positioned to receive actively projected images into the optical waveguide prism from an active image source and the second major surface of the optical waveguide prism is positioned to receive images of a real-world ambient environment into the optical waveguide prism, which real-world ambient environment is external to the image display system.

20. The image display system of claim 16, further comprising:

a freeform compensation lens having a first major surface and a second major surface, the first major surface of the compensation lens having a shape that at least approximately matches a shape of the second major surface of the optical waveguide prism, the freeform compensation lens positioned relatively outwardly of the second major surface of the optical waveguide prism toward the real-world ambient environment to form a gap between the first major surface of the compensation lens and the second major surface of the optical waveguide prism.

21. The image display system of claim 16 wherein a shape, an optical path length, and a thickness of the optical waveguide prism are optimized for a wrapped-around design that ergonomic fits a human head.

22. The image display system of claim 16 wherein a width of the optical waveguide prism at least approximately fits a width of an average human head.

23. The image display system of claim 16 wherein the first major surface of the optical waveguide prism is curved about an axis.

24. The image display system of claim 16 wherein each point on the second major surface of the optical waveguide prism is no greater than 30 mm of a corresponding point on the first major surface of the optical waveguide prism.

25. The image display system of claim 16 wherein each point on the second major surface of the optical waveguide prism is no greater than 12 mm of a corresponding point on the first major surface of the optical waveguide prism.

26. The image display system of claim 16 wherein the second major surface of the optical waveguide prism comprises a plurality of surface segments, each surface segment having a unique set of parameters.

27. The image display system of claim 16, further comprising:

an image display unit positioned and oriented to provide images into the optical waveguide prism; and

at least one adjustable coupling lens that guides light from the image display unit into the optical waveguide prism and corrects for optical aberrations.

28. A freeform compensation lens for use in an image display system along with a freeform optical waveguide prism having a first major surface and a second major surface, the freeform compensation lens comprising:

a first major surface;

a second major surface; and

an interior space between the first and the second major surfaces of the compensation lens comprising a refractive medium having an index greater than one.

29. The freeform compensation lens of claim 28 wherein the compensation lens is physically coupled to the optical waveguide prism spaced relatively outwardly of the second major surface of the optical waveguide prism toward a real-world ambient environment with a gap between the first major surface of the compensation lens and the second major surface of the optical waveguide prism.

30. The freeform compensation lens of claim 29 wherein the first major surface of the compensation lens has a shape that approximately matches a shape of the second major surface of the optical waveguide prism.

31. The freeform compensation lens of claim 28 wherein each point on the first major surface of the optical waveguide prism is no greater than 30 mm of a corresponding point on the second major surface of the optical waveguide prism.

32. The freeform compensation lens of claim 28 wherein each point on the first major surface of the optical waveguide prism is no greater than 12 mm of a corresponding point on the second major surface of the optical waveguide prism.