Transmissive optical element based on reflective volumetric gratings

Patent metadata

Field	Value
Publication number	US-12535682-B2
Application number	US-202217590692-A
Country	US
Kind code	B2
Filing date	Feb 1, 2022
Priority date	Jan 11, 2022
Publication date	Jan 27, 2026
Grant date	Jan 27, 2026

Abstract

A transmissive optical element includes first and second reflective volumetric gratings that redirect an impinging light beam in a first wavelength range from the first grating to the second grating by reflective diffraction, and from the second grating out of the transmissive optical element, also by reflective diffraction. Such a configuration enables the transmissive optical element to transmit a light cone in a second, different wavelength range substantially without redirecting the light cone, while redirecting the impinging light beam at the same time. The transmissive optical element may be used in a visual display e.g. to separate paths of image light in visible part of light spectrum and some service light in a different part of the light spectrum.

First claim

What is claimed is:

1 . A transmissive optical element for redirecting a light beam in a first wavelength range while transmitting light without redirection by diffraction in a second wavelength range, different from the first wavelength range, and within an angular range, the transmissive optical element comprising:
a first outer surface for receiving the light beam at a first beam angle; a second outer surface opposing the first outer surface, for outputting the light beam through at a second, different beam angle; a first volumetric grating between the first and second outer surfaces for redirecting, by reflective diffraction, the light beam propagated through the first outer surface; and a second volumetric grating between the first and second outer surfaces for transmitting the light beam propagated through the first outer surface, for receiving the light beam redirected by the first volumetric grating, and for redirecting, by reflective diffraction, the light beam to propagate through the first volumetric grating, through the second outer surface, and out of the transmissive optical element at the second beam angle.

2 . The transmissive optical element of claim 1 for use in a visual display, wherein the angular range comprises a field of view of the visual display.

3 . The transmissive optical element of claim 2 , wherein the field of view is at least +/−15 degrees in each one of vertical and horizontal directions.

4 . The transmissive optical element of claim 1 , wherein the first wavelength range is an infrared wavelength range comprising wavelengths greater than 710 nm, and the second wavelength range is a visible wavelength range comprising wavelengths between 390 nm and 710 nm.

5 . The transmissive optical element of claim 1 , wherein the first volumetric grating is disposed proximate the second outer surface, and the second volumetric grating is disposed proximate the first outer surface.

6 . The transmissive optical element of claim 1 , wherein the first and second volumetric gratings overlap within the transmissive optical element.

7 . The transmissive optical element of claim 1 , comprising an even number of volumetric gratings including the first and second volumetric gratings, for redirecting the light beam within the transmissive optical element by reflective diffraction.

8 . The transmissive optical element of claim 1 , wherein at least one of the first and second volumetric gratings comprises a volume Bragg grating.

9 . The transmissive optical element of claim 1 , wherein at least one of the first and second volumetric gratings has at least one of a spatially varying pitch or a spatially varying fringe slant angle to provide a spatially varying angle of redirection of the light beam by the transmissive optical element.

10 . A near-eye display comprising:
a display module for providing image light to an eyebox; and a transmissive optical element in an optical path of the image light for redirecting an infrared light beam while transmitting the image light to the eyebox, the transmissive optical element comprising:
a first outer surface for receiving the infrared light beam at a first beam angle;
a second outer surface opposing the first outer surface, for outputting the infrared light beam through at a second beam angle, different from the first beam angle;
a first volumetric grating between the first and second outer surfaces for redirecting, by reflective diffraction, the infrared light beam propagated through the first outer surface; and
a second volumetric grating between the first and second outer surfaces for transmitting the infrared light beam propagated through the first outer surface, for receiving the infrared light beam redirected by the first volumetric grating and for redirecting, by reflective diffraction, the infrared light beam to propagate through the first volumetric grating, through the second outer surface, and out of the transmissive optical element at the second beam angle.

11 . The near-eye display of claim 10 , wherein the first outer surface of the transmissive optical element faces the eyebox, and wherein the infrared light beam carries an image of a viewer's eye at the eyebox, the near-eye display further comprising an eye imager for imaging the viewer's eye, wherein the transmissive optical element is configured to redirect the infrared light beam to impinge onto the eye imager to detect the image of the viewer's eye.

12 . The near-eye display of claim 11 , wherein the infrared light beam comprises wavelengths greater than 710 nm, and wherein the image light is within a wavelength range between 390 nm and 710 nm.

13 . The near-eye display of claim 10 , wherein the first volumetric grating is disposed proximate the second outer surface, and the second volumetric grating is disposed proximate the first outer surface.

14 . The near-eye display of claim 10 , wherein the first and second volumetric gratings overlap within the transmissive optical element.

15 . The near-eye display of claim 10 , comprising an even number of volumetric gratings including the first and second volumetric gratings, for redirecting the infrared light beam within the transmissive optical element by reflective diffraction.

16 . The near-eye display of claim 10 , wherein at least one of the first and second volumetric gratings comprises a volume Bragg grating.

17 . A method for imaging a viewer's eye in a near-eye display, the method comprising:
illuminating the viewer's eye with auxiliary light; redirecting the auxiliary light reflected from the viewer's eye using a transmissive optical element in an optical path of image light carrying images to be viewed by the viewer's eye, the redirecting comprising:
redirecting the auxiliary light by reflective diffraction on a first volumetric grating of the transmissive optical element; and
redirecting the auxiliary light redirected by the first volumetric grating by reflective diffraction on a second volumetric grating of the transmissive optical element to propagate through the first volumetric grating and exit the transmissive optical element; and
detecting the auxiliary light redirected by the transmissive optical element to obtain an image of the viewer's eye; wherein at least one of the first and second volumetric gratings comprises a polarization volume hologram grating configured to selectively redirect light of a first polarization state while substantially transmitting light of a second, orthogonal polarization state.

18 . The method of claim 17 , wherein the transmissive optical element redirects the auxiliary light away from the optical path of the image light.

19 . The method of claim 17 , wherein the transmissive optical element is configured to substantially not deviate or absorb the image light.

20 . The method of claim 19 , wherein the image light provides a field of view of at least +/−15 degrees in each one of vertical and horizontal directions.

Assignees

• Meta Platforms Tech Llc

Inventors

• Trochtchanovitch Pavel
• Sulai Yusufu Njoni Bamaxam
• Yun Zhisheng

Classifications

• G02B2027/0178

  Eyeglass type (eyeglass details G02C) · CPC title

• G02B27/0172 Primary

  characterised by optical features · CPC title

• G02B27/0037

  with diffracting elements (G02B27/0056 takes precedence; holographic optical elements G02B5/32; zone systems G02B5/1876) · CPC title

• G02B5/32

  Holograms used as optical elements · CPC title

• G02B5/188

  Plurality of such optical elements formed in or on a supporting substrate · CPC title