Grating arrangements

Patent metadata

Field	Value
Publication number	US-2022099990-A1
Application number	US-202017424133-A
Country	US
Kind code	A1
Filing date	Apr 15, 2020
Priority date	Apr 16, 2019
Publication date	Mar 31, 2022
Grant date	—

Abstract

The invention concerns a diffractive waveguide element for a personal display device, the element comprising a waveguide body (21), and at least two grating regions (23, 24) arranged on the waveguide body (21), at least some of the grating regions adapted to expand the exit pupil of the element. According to the invention, the grating regions (23, 24) are positioned with respect to each other so that and are provided with gratings having different grating vectors so that the grating regions (23, 24) interact to combine the functions of exit pupil expansion and outcoupling on at least some parts of the element. The invention allows for efficient use of waveguide area.

First claim

1 . A diffractive waveguide element for a personal display device, comprising:
a waveguide body, and at least two grating regions arranged on the waveguide body, at least some of the grating regions adapted to expand the exit pupil of the element, wherein:
the grating regions are positioned with respect to each other so that and are provided with gratings having different grating vectors so that the grating regions interact to combine the functions of exit pupil expansion and out-coupling on at least some parts of the element,
a first and a second grating regions are arranged at a distance from each other in the main plane of the waveguide,
there is provided a third grating region having a third grating between the first and second grating regions,
the third grating is a doubly periodic grating,
the first, second and third grating regions are arranged on the same side of the waveguide body, and
there is a fourth grating region arranged on the opposite surface of the waveguide body, the fourth grating region comprising a fourth grating being configured to expand exit pupil of rays having a small wave vector component in one dimension.

2 . The element according to claim 1 , wherein:
the first grating region is provided with the first grating, the first grating region being positioned on a first location of the waveguide body, and the second grating region is provided with the second grating, the second grating region being positioned on a second location of the waveguide body, different from the first location, whereby the second grating is arranged to out-couple rays turned by the first grating and vice versa.

3 . The element according to claim 2 , further comprising an in-coupling grating adapted to diffract light directed thereto from the outside of the waveguide body towards the first and second grating regions, the in-coupling grating, first grating and second grating being chosen so that their sum grating vector is a zero vector.

4 . The element according to claim 1 , wherein the fourth grating region is arranged in non-overlapping manner to the first, second or third grating region on the different side of the waveguide body.

5 . The element according to claim 1 , wherein the grating regions are arranged on different sides of the waveguide body so that the fourth grating region partially overlaps the first, second and third grating regions in the main plane of the waveguide.

6 . The element according to claim 1 , wherein the first, second, third and/or fourth gratings are linear gratings.

7 . The element according to claim 1 , wherein the doubly periodic grating is as a hexagonal grating.

8 . (canceled)

9 . The element according to claim 7 , wherein the fourth grating is a linear grating having a period smaller than the first and second gratings.

10 . The element according to claim 9 , further comprising at least one doubly periodic in-coupling grating, such as a hexagonal grating, adapted to diffract light directed thereto from the outside of the waveguide body towards the first, second, third and fourth grating regions.

11 . (canceled)

12 . The element according to claim 10 , further comprising two such in-coupling gratings arranged on different lateral sides of the first and second grating regions.

13 . The element according to claim 12 , wherein the in-coupling gratings are arranged non-aligned with each other on different lateral sides of the first and second grating regions.

14 .- 17 . (canceled)

18 . The element according to claim 1 , wherein one of the grating regions comprises a void, i.e. a sub-region without grating, on one side of the waveguide body, aligned with a linear grating provided on the opposite side of the waveguide body.

19 . A personal display device comprising:
a waveguide element according to claim 1 , and at least one projector for directing an image on the in-coupling grating, from which it is diffracted into the waveguide and proceeds to the first and second grating regions, where the exit pupil is expanded and image out-coupled due to the first and second gratings.

20 . A method of providing an image on a personal see-through display device, the method comprising:
coupling an image into a waveguide body using an in-coupler as propagating rays, allowing the exit pupil of a first part of the in-coupled propagating rays to expand in the waveguide by means of a first grating arranged on the waveguide, from which the expanded rays propagate to a second grating arranged on the waveguide and having a different grating vector than the first grating so as to out-couple therefrom, and allowing the exit pupil of a second part, different from the first part, of the in-coupled propagating rays to expand in the waveguide by means of the second grating, from which the expanded rays propagate to the first grating so as to out-couple therefrom, wherein allowing the exit pupil of rays having a small wave vector component in one dimension to be expanded by an additional grating having a period shorter than the first and second gratings.

21 . (canceled)

22 . The element according to claim 2 , wherein the fourth grating region is arranged in non-overlapping manner to the first, second or third grating region on the different side of the waveguide body.

23 . The element according to claim 2 , wherein the grating regions are arranged on different sides of the waveguide body so that the fourth grating region partially overlaps the first, second and third grating regions in the main plane of the waveguide.

24 . The element according to claim 2 , wherein the first, second, third and/or fourth gratings are linear gratings.

25 . The element according to claim 1 , wherein the fourth grating is a linear grating having a period smaller than the first and second gratings.

26 . The element according to claim 25 , further comprising at least one doubly periodic in-coupling grating, such as a hexagonal grating, adapted to diffract light directed thereto from the outside of the waveguide body towards the first, second, third and fourth grating regions.

27 . The element according to claim 1 , further comprising at least one doubly periodic in-coupling grating, such as a hexagonal grating, adapted to diffract light directed thereto from the outside of the waveguide body towards the first, second, third and fourth grating regions.

Assignees

• Dispelix Oy

Inventors

• Olkkonen Juuso

Classifications

• G02B6/34

  utilising prism or grating {(G02B6/293 takes precedence)} · CPC title

• G02B2027/0123

  comprising devices increasing the field of view · CPC title

• G02B27/4205 Primary

  having a diffractive optical element [DOE] contributing to image formation, e.g. whereby modulation transfer function MTF or optical aberrations are relevant · CPC title

• G02B27/0172 Primary

  characterised by optical features · CPC title

• G02B5/1866

  Transmission gratings characterised by their structure, e.g. step profile, contours of substrate or grooves, pitch variations, materials (G02B5/1809, G02B5/1828, G02B5/1833, G02B5/1838 and G02B5/1847 take precedence) · CPC title