Low-profile beam splitter

• US 10,564,533 B2
• Filed: 03/21/2018
• Issued: 02/18/2020
• Est. Priority Date: 03/21/2017
• Status: Active Grant

• Current Assignee: Magic Leap, Inc.
• Original Assignee: Magic Leap, Inc.
• Inventors: Trisnadi, Jahja, St. Hilaire, Pierre, Cheng, Hui-Chuan, Carlisle, Clinton, Klug, Michael Anthony, Curtis, Kevin Richard
• Primary Examiner(s): Dowling, William C.
• Application Number:
  US15/927,807
• Publication Number:
  US 20180284585A1
• Time in Patent Office: 699 Days
• CPC Class Codes: G02B 2027/0127 comprising devices increasing the depth of field
• CPC Class Codes: G02B 2027/0134 of stereoscopic type
• CPC Class Codes: G02B 2027/0138 comprising image capture systems, e.g. camera
• CPC Class Codes: G02B 2027/0174 holographic
• CPC Class Codes: G02B 2027/0185 Displaying image at variable distance
• CPC Class Codes: G02B 26/103 having movable or deformable optical fibres, light guides or waveguides as scanning elements light guides per se G02B6/00
• CPC Class Codes: G02B 27/0103 comprising holographic elements
• CPC Class Codes: G02B 27/017 Head mounted
• CPC Class Codes: G02B 27/0944 Diffractive optical elements, e.g. gratings, holograms gratings per se G02B5/18; holograms used as optical elements per se G02B5/32
• CPC Class Codes: G02B 27/1006 for splitting or combining different wavelengths G02B27/1086, G02B27/141 take precedence
• CPC Class Codes: G02B 27/1033 having a single light modulator for all colour channels
• CPC Class Codes: G03B 21/005 Projectors using an electronic spatial light modulator but not peculiar thereto
• CPC Class Codes: G03B 21/2066 Reflectors in illumination beam in projection beam G03B21/28
• CPC Class Codes: G06V 20/20 in augmented reality scenes
• CPC Class Codes: G06V 40/19 Sensors therefor

Abstract

Examples of light projector systems for directing input light from a light source to a spatial light modulator are provided. For example, an optical device is disclosed which includes a first surface having a diffractive optical element, a second surface normal to the first surface, and a third surface arranged at an angle to the second surface. The third surface may be a beam splitting surface that is reflective to light of a first state and transmissive to light of a second state. The diffractive optical element may receive an input beam made up of light having the first state, and convert the input beam into at least a first diffracted beam at a first diffraction angle such that the first diffracted beam is directed toward the third surface and is reflected by the third surface in a direction substantially parallel to the first surface.

Claims

1. An optical device comprising:

a first surface comprising a transmissive diffractive optical element;

a second surface normal to the first surface; and

a third surface arranged at an angle to the second surface, the third surface being reflective to light of a first state and transmissive to light of a second state,

wherein the transmissive diffractive optical element is configured to receive a collimated input beam that is normally incident on the first surface, the collimated input beam comprising light having the first state, and to convert the collimated input beam into at least a first diffracted beam at a first diffraction angle such that the first diffracted beam is directed toward the third surface and is reflected by the third surface in a direction substantially parallel to the first surface.

2. The optical device of claim 1, wherein the first diffracted beam exits the optical device at the second surface, the optical device further comprising a spatial light modulator adjacent to the second surface to receive the first diffracted beam, the spatial light modulator configured to convert the first diffracted beam into a first modulated beam, the first modulated beam comprising light having the second state, and to direct the first modulated beam back toward the second surface.

3. The optical device of claim 2, wherein the spatial light modulator is a liquid crystal on silicon (LCOS) spatial light modulator or a digital light processing (DLP) spatial light modulator.

4. The optical device of claim 2, further comprising a fourth surface opposite the second surface, wherein the fourth surface is configured to receive and transmit the first modulated beam after it passes through the second surface, and wherein the fourth surface is curved.

5. The optical device of claim 1, wherein the transmissive diffractive optical element is further configured to convert the collimated input beam into a second diffracted beam at a second diffraction angle such that the second diffracted beam is directed toward the second surface, is reflected by the second surface toward the third surface via total internal reflection, and is reflected by the third surface in the direction substantially parallel to the first surface.

6. The optical device of claim 5, wherein the reflected first diffracted beam and the reflected second diffracted beam are received by a spatial light modulator, wherein the reflected first diffracted beam and the reflected second diffracted beam combine to illuminate the entire spatial light modulator.

7. The optical device of claim 1, wherein the first, second, and third surfaces are planar.

8. The optical device of claim 1, wherein the second surface is a curved surface.

9. The optical device of claim 1, wherein the first, second, and third surfaces form a wedge.

10. The optical device of claim 9, wherein the wedge comprises a refractive index of at least approximately 1.5.

11. The optical device of claim 1, wherein the third surface comprises a polarizing beam splitting surface.

12. The optical device of claim 1, wherein the angle of the third surface with respect to the second surface is less than 45 degrees.

13. The optical device of claim 12, wherein the angle of the third surface with respect to the second surface is about 30 degrees.

14. The optical device of claim 1, wherein the first diffraction angle is greater than 0 degrees.

15. The optical device of claim 14, wherein the first diffraction angle is about 30 degrees.

16. The optical device of claim 1, wherein the transmissive diffractive optical element comprises a plurality of diffractive features.

17. The optical device of claim 16, wherein the first diffraction angle is based on a period of the plurality of diffractive features.

18. An optical device comprising:

a first surface comprising a reflective diffractive optical element;

a second surface normal to the first surface; and

a third surface arranged at an angle to the second surface, the third surface being reflective to light of a first state and transmissive to light of a second state;

wherein the reflective diffractive optical element is configured to receive a diverging input beam, the diverging input beam comprising light having the first state, and to convert the diverging input beam into at least a first collimated and diffracted beam at a first diffraction angle such that the first collimated and diffracted beam is directed toward the third surface and is reflected by the third surface in a direction substantially parallel to the first surface.

19. The optical device of claim 18, wherein the first collimated and diffracted beam exits the optical device at the second surface, the optical device further comprising a spatial light modulator adjacent to the second surface to receive the first collimated and diffracted beam, the spatial light modulator configured to convert the first collimated and diffracted beam into a first modulated beam, the first modulated beam comprising light having the second state, and to direct the first modulated beam back toward the second surface.

20. The optical device of claim 19, wherein the spatial light modulator is a liquid crystal on silicon (LCOS) spatial light modulator or a digital light processing (DLP) spatial light modulator.

21. The optical device of claim 19, further comprising a fourth surface opposite the second surface, wherein the fourth surface is configured to receive and transmit the first modulated beam after it passes through the second surface, and wherein the fourth surface is curved.

22. The optical device of claim 18, wherein the reflective diffractive optical element is further configured to convert the diverging input beam into a second collimated and diffracted beam at a second diffraction angle such that the second collimated and diffracted beam is directed toward the second surface, is reflected by the second surface toward the third surface via total internal reflection, and is reflected by the third surface in the direction substantially parallel to the first surface.

23. The optical device of claim 22, wherein the reflected first collimated and diffracted beam and the reflected second collimated and diffracted beam are received by a spatial light modulator, wherein the reflected first collimated and diffracted beam and the reflected second collimated and diffracted beam combine to illuminate the entire spatial light modulator.

24. The optical device of claim 18, wherein the reflective diffractive optical element is configured to receive a plurality of angularly or laterally separated diverging input beams and to convert them into collimated and diffracted beams with a reduced amount of angular or lateral separation.

25. The optical device of claim 24, further comprising a plurality of laterally separated light sources to output the plurality of angularly or laterally separated diverging input beams.

26. The optical device of claim 24, wherein the reflective diffractive optical element is configured to receive a first input beam of the a plurality of angularly or laterally separated diverging input beams at a first angle and to convert the first input beam into a corresponding first collimated and diffracted beam directed toward the third surface along an optical path, and to receive a second input beam of the a plurality of angularly or laterally separated diverging input beams at a second angle and to convert the second input beam into a second collimated and diffracted beam directed toward the third surface along the optical path.

27. The optical device of claim 18, wherein the first, second, and third surfaces are planar.

28. The optical device of claim 18, wherein the second surface is a curved surface.

29. The optical device of claim 18, wherein the first, second, and third surfaces form a wedge.

30. The optical device of claim 29, wherein the wedge comprises a refractive index of at least approximately 1.5.

31. The optical device of claim 18, wherein the third surface comprises a polarizing beam splitting surface.

32. The optical device of claim 18, wherein the angle of the third surface with respect to the second surface is less than 45 degrees.

33. The optical device of claim 32, wherein the angle of the third surface with respect to the second surface is about 30 degrees.

34. The optical device of claim 18, wherein the first diffraction angle is greater than 0 degrees.

35. The optical device of claim 34, wherein the first diffraction angle is about 30 degrees.

36. The optical device of claim 18, wherein the first diffraction angle is based on a period of diffractive features of the reflective diffractive optical element.

37. The optical device of claim 18, wherein the reflective diffractive optical element comprises a hologram.

38. A head mounted display (HMD) configured to be worn on a head of a user, the HMD comprising:

a frame;

projection optics supported by the frame and configured to project an image to an eye of the user; and

a light projector system in optical communication with the projection optics, the light projector system configured to provide modulated light encoded with the image, the light projector system comprising;

a light source to emit an input beam;

an optical device comprising;

a first surface with a diffractive optical element,

a second surface normal to the first surface, and

a third surface arranged at an angle to the second surface, the third surface being reflective to light of a first state and transmissive to light of a second state,

wherein the diffractive optical element is configured to receive the input beam, the input beam comprising light having the first state, and to convert the input beam into at least a first diffracted beam at a first diffraction angle such that the first diffracted beam is directed toward the third surface and is reflected by the third surface in a direction substantially parallel to the first surface; and

a spatial light modulator configured to produce the modulated light using the input beam delivered to the spatial light modulator by the optical device.

39. The HMD of claim 38, wherein the diffractive optical element comprises a transmissive diffractive optical element.

40. The HMD of claim 38, wherein the diffractive optical element comprises a reflective diffractive optical element.

41. The HMD of claim 38, wherein the diffractive optical element comprises a diffraction grating.

42. The HMD of claim 38, wherein the diffractive optical element comprises a hologram.

43. The HMD of claim 38, further comprising a collimator disposed between the optical device and the light source.

44. The HMD of claim 38, wherein the projection optics comprise:

in-coupling optical elements; and

out-coupling optical elements,

wherein the in-coupling optical elements are configured to receive and in-couple the modulated light, and

wherein the out-coupling optical elements are configured to out-couple the in-coupled light towards the eye of the user.

45. The HMD of claim 44, wherein the projection optics comprises a stack of waveguides.

46. The HMD of claim 45, wherein each waveguide is configured to out-couple light with a different amount of divergence in comparison to one or more other waveguides of the stack of waveguides.

47. An optical device comprising:

a first surface comprising a diffractive optical element;

a second surface normal to the first surface; and

a third surface arranged at an angle to the second surface, the third surface being reflective to light of a first state and transmissive to light of a second state,

wherein the diffractive optical element is configured to receive an input beam, the input beam comprising light having the first state, and to convert the input beam into at least a first diffracted beam at a first diffraction angle such that the first diffracted beam is directed toward the third surface and is reflected by the third surface in a direction substantially parallel to the first surface.

48. The optical device of claim 47, wherein the diffractive optical element comprises a transmissive diffractive optical element.

49. The optical device of claim 47, wherein the diffractive optical element comprises a reflective diffractive optical element.

50. The optical device of claim 47, wherein the diffractive optical element comprises a diffraction grating.

51. The optical device of claim 47, wherein the diffractive optical element comprises a hologram.

52. The optical device of claim 47, wherein the input beam is collimated by a collimator separate from the optical device.

53. The optical device of claim 47, wherein the diffractive optical element is configured to convert the input beam into a first collimated and diffracted beam.

54. The optical device of claim 47, wherein the first and second states are a first polarization state and a second polarization state, respectively.