Waveguide display element with an intermediate layer between an in-coupling grating and a waveguide

Patent metadata

Field	Value
Publication number	US-11067733-B2
Application number	US-201917041292-A
Country	US
Kind code	B2
Filing date	Mar 22, 2019
Priority date	Mar 28, 2018
Publication date	Jul 20, 2021
Grant date	Jul 20, 2021

Abstract

A waveguide display element includes waveguide layers stacked on top of each other and an in-coupler associated with each waveguide layer for coupling light within a predefined wavelength band into the waveguide layer. Each of the in-couplers includes an intermediate layer arranged on the waveguide layer, the intermediate layer having intermediate layer properties. Each of the in-couplers further includes an in-coupling grating arranged on the intermediate layer, the grating having grating properties. The combination of the intermediate layer properties and grating properties of each in-coupler is different with respect to other in-couplers.

First claim

The invention claimed is:

1. A waveguide display element comprising:
a plurality of waveguide layers stacked on top of each other, and
an in-coupler associated with each waveguide layer for coupling light within a predefined wavelength band into the waveguide layer,
wherein:
each of the in-couplers includes:
an intermediate layer arranged on the waveguide layer, the intermediate layer having intermediate layer properties, and
an in-coupling grating arranged on the intermediate layer, the grating having grating properties, and

the combination of intermediate layer properties and grating properties of each in-coupler is different with respect to other in-couplers.

2. The element according to claim 1 , wherein the in-couplers have the same intermediate layer properties and different grating properties with respect to other in-couplers.

3. The element according to claim 2 , wherein in-couplers associated with different waveguide layers have different in-coupling grating periods.

4. The element according to claim 3 , wherein the grating period increases from a top waveguide layer on the incoming light side of the element towards a bottom waveguide layers on the opposite side of the element.

5. The element according to claim 2 , wherein the grating period increases from a top waveguide layer on the incoming light side of the element towards a bottom waveguide layers on the opposite side of the element.

6. The element according to claim 2 , wherein the intermediate layers of each in-coupler have a thickness of 20 μm or less, in particular 10 μm or less, such as 1-10 μm.

7. The element according to claim 2 , wherein:
the waveguide layers have an index of refraction which is 1.7 or more, such as 2.0 or more, and the intermediate layers have an index of refraction which is less than 1.8, such as 1.7 or less.

8. The element according to claim 2 , wherein the in-couplers have the same shape and are aligned with each other in the lateral plane of the element.

9. The element according to claim 1 , wherein in-couplers associated with different waveguide layers have different in-coupling grating periods.

10. The element according to claim 9 , wherein the grating period increases from a top waveguide layer on the incoming light side of the element towards a bottom waveguide layers on the opposite side of the element.

11. The element according to claim 9 , wherein the grating period increases from a top waveguide layer on the incoming light side of the element towards a bottom waveguide layers on the opposite side of the element.

12. The element according to claim 1 , wherein the in-couplers have the same grating properties and different intermediate layer properties with respect to other in-couplers.

13. The element according to claim 12 , further comprising one or more optical bandpass filters or dichroic mirrors between the waveguide layers.

14. The element according to claim 1 , wherein the intermediate layers of each in-coupler have a thickness of 20 μm or less, in particular 10 μm or less, such as 1-10 μm.

15. The element according to claim 1 , wherein:
the waveguide layers have an index of refraction which is 1.7 or more, such as 2.0 or more, and
the intermediate layers have an index of refraction which is less than 1.8, such as 1.7 or less.

16. The element according to claim 1 , wherein the in-couplers have the same shape and are aligned with each other in the lateral plane of the element.

17. A personal display device, such as a head-mounted display or head-up display, comprising:
a waveguide display element according to claim 1 , and
a multicolor laser projector adapted to project light rays in different angles of incidence to in-couplers of the display element.

18. A method of coupling propagating light rays into a waveguide display, comprising:
providing a waveguide display element according to claim 1 , and
directing light rays in different angles of incidence to the display element in order to selectively couple said rays into the different waveguide layers of the display element.

19. The method according to claim 18 , wherein said light rays comprise light rays in at least three different wavelength bands, each of the wavelength bands being directed to the display element in a different angle of incidence.

20. The element according to claim 1 , wherein each intermediate layer has a thickness and index of refraction smaller than that of the waveguide layer it is associated with.

Assignees

• Dispelix Oy

Inventors

• Olkkonen Juuso
• Blomstedt Kasimir

Classifications

• G02B2027/0114

  comprising dichroic elements · CPC title

• G02B27/4272

  having plural diffractive elements positioned sequentially along the optical path · CPC title

• G02B27/0172 Primary

  characterised by optical features · CPC title

• G02B6/29329

  Diffractive elements operating in transmission · CPC title

• G02B6/0076

  Stacked arrangements of multiple light guides of the same or different cross-sectional area · CPC title