Prism beam expander

Patent metadata

Field	Value
Publication number	US-11719947-B1
Application number	US-202016871063-A
Country	US
Kind code	B1
Filing date	May 11, 2020
Priority date	Jun 30, 2019
Publication date	Aug 8, 2023
Grant date	Aug 8, 2023

Abstract

An optical component includes a block of a transparent material, having a trapezoidal cross-section defined by first and second parallel, rectangular faces on mutually-opposing sides of the block and third and fourth faces oriented diagonally at opposing ends of the first and second faces. One or more planar, partially-reflecting layers extend within the block between the third and fourth faces in an orientation parallel to the first and second faces.

First claim

The invention claimed is:

1. An optical component, comprising:
a block of a transparent material, having a trapezoidal cross-section defined by first and second parallel, rectangular faces on mutually-opposing sides of the block and third and fourth faces oriented diagonally at opposing ends of the first and second faces; and
one or more planar, partially-reflecting layers extending within the block between the third and fourth faces in an orientation parallel to the first and second faces.

2. The optical component according to claim 1 , wherein the trapezoidal cross-section comprises a parallelogram.

3. The optical component according to claim 1 , wherein the trapezoidal cross-section comprises an isosceles trapezoid.

4. The optical component according to claim 1 , and comprising an anti-reflective coating on the third and fourth faces.

5. The optical component according to claim 1 , wherein the first and second faces are configured to reflect internally rays of light that impinge on the first and second faces after passing through the partially-reflecting layers.

6. The optical component according to claim 5 , and comprising a reflective coating on the first and second faces.

7. The optical component according to claim 1 , wherein the one or more planar, partially-reflecting layers comprise multiple planar, partially-reflecting layers, which are parallel to and spaced apart between the first and second faces.

8. The optical component according to claim 6 , wherein a spacing between the partially-reflecting layers does not exceed one-fifth of a length of the second face.

9. The optical component according to claim 1 , wherein a height of the block between the first and second faces does not exceed one fifth of a length of the second face.

10. Image projection apparatus, comprising:
an optical pupil expander, comprising:
a block of a transparent material, having a trapezoidal cross-section defined by first and second parallel, rectangular faces on mutually-opposing sides of the block and third and fourth faces oriented diagonally at opposing ends of the first and second faces; and
one or more planar, partially-reflecting layers extending within the block between the third and fourth faces in an orientation parallel to the first and second faces; and

an image projector, which is configured to project a beam of light onto the third face of the block with a given input beam width, at an angle selected so that the beam is reflected internally within the block while being partially reflected and partially transmitted multiple times by the one or more planar, partially-reflecting layer, and exits through the fourth face with an output beam width at least twice the input beam width.

11. The apparatus according to claim 10 , wherein the optical pupil expander is configured to homogenize an intensity of the light in the output beam.

12. The apparatus according to claim 10 , wherein the angle is selected so that the beam is reflected from the first and second faces of the block by total internal reflection.

13. A method for image projection, comprising:
providing an optical pupil expander, comprising:
a block of a transparent material, having a trapezoidal cross-section defined by first and second parallel, rectangular faces on mutually-opposing sides of the block and third and fourth faces oriented diagonally at opposing ends of the first and second faces; and
one or more planar, partially-reflecting layers extending within the block between the third and fourth faces in an orientation parallel to the first and second faces; and

projecting a beam of light onto the third face of the block with a given input beam width, at an angle selected so that the beam is reflected internally within the block while being partially reflected and partially transmitted multiple times by the one or more planar, partially-reflecting layer, and exits through the fourth face with an output beam width at least twice the input beam width.

14. The method according to claim 13 , wherein projecting the beam of light comprises homogenizing an intensity of the light in the output beam.

15. The method according to claim 13 , wherein projecting the beam of light comprises selecting the angle so that the beam is reflected from the first and second faces of the block by total internal reflection.

16. The method according to claim 13 , wherein the trapezoidal cross-section comprises a parallelogram.

17. The method according to claim 13 , wherein the trapezoidal cross-section comprises an isosceles trapezoid.

18. The method according to claim 13 , wherein the one or more planar, partially-reflecting layers comprise multiple planar, partially-reflecting layers, which are parallel to and spaced apart between the first and second faces, wherein a spacing between the partially-reflecting layers does not exceed one-fifth of a length of the second face.

19. The method according to claim 13 , wherein a height of the block between the first and second faces does not exceed one fifth of a length of the second face.

20. The method according to claim 13 , wherein providing the optical pupil expander comprises providing a plurality of sub-blocks of the transparent material, coating a surface of at least one of the sub-blocks with the one or more planar, partially-reflecting layers, and cementing the sub-blocks together to form the block of the transparent material.

Assignees

• Apple Inc

Inventors

• Hajati Arman
• Hansotte Eric J
• Upton Robert S

Classifications

• G02B27/0983 Primary

  being curved · CPC title

• B23K26/0732

  into a rectangular shape · CPC title

• G02B27/0927

  Systems for changing the beam intensity distribution, e.g. Gaussian to top-hat · CPC title

• G02B27/0081

  with means for altering, e.g. enlarging, the entrance or exit pupil · CPC title

• G02B27/0172

  characterised by optical features · CPC title