Improved brightness waveguide display

Patent metadata

Field	Value
Publication number	US-2021088791-A1
Application number	US-201816954865-A
Country	US
Kind code	A1
Filing date	Dec 18, 2018
Priority date	Dec 22, 2017
Publication date	Mar 25, 2021
Grant date	—

Abstract

The invention relates to a diffractive waveguide display element comprising a waveguide body (13) having a first surface and a second surface opposite to the first surface, an outcoupling-diffractive optical element on said first surface for coupling light propagating inside the waveguide body out of the waveguide body, and a narrow-band reflector element (21) on said second surface. The invention also relates to a display device comprising such element.

First claim

1 . A diffractive waveguide display element comprising:
a waveguide body having a first surface and a second surface opposite to the first surface, an out-coupling diffractive optical element on said first surface for coupling light propagating inside the waveguide body out of the waveguide body, and a narrow-band reflector element, wherein the reflector element is positioned on said second surface and has laterally non-uniform optical properties.

2 . The element according to claim 1 , wherein the reflector element is a single-band reflector element.

3 . The element according to claim 1 , wherein the reflector element is a multi-band reflector element.

4 . The element according to claim 1 , wherein the reflector element has one or more wavelength bands having an FWHM of 50 nm or less, such as 20 nm or less.

5 . The element according to claim 1 , wherein the reflector element has a total white light transmittance of at least 50%.

6 . The element according to claim 1 , wherein the reflector element comprises a dielectric multilayer structure, having a stack of alternating layers having different indices of refraction.

7 . The element according to claim 1 , wherein the reflector element comprises semi-transparent metallic layer, in particular a single layer, such as a layer having a thickness of 20 nm or less.

8 . The element according to claim 1 , wherein the reflector element is optically insulated from the waveguide body.

9 . The element according to claim 1 , wherein the reflector element is separated from the waveguide body by an air gap or aerogel layer.

10 . The element according to claim 1 , wherein the reflector element comprises a plurality of distinct segments positioned laterally adjacent to each other, the segments having different reflectances and/or wavelength characteristics.

11 . The element according to claim 1 , wherein the reflector element contains a first region and a second region downstream of the first region in the propagation direction of light in the waveguide body, and the reflectance of the second region is higher than the reflectance of the first region.

12 . A see-through display device, comprising:
a diffractive waveguide display element, and a narrow-band projector, such as a laser projector or narrow-band LED projector, comprising at least one narrow-band light source having an output wavelength, wherein:
the projector is configured to couple an image to be displayed into the waveguide body for propagation therein and for further exiting the waveguide body to an eye of a user of the display device, and
the display element is an element according to any of the preceding claims, whereby said exiting is configured to occur partially directly from the out-coupling grating and partially through reflection from the reflector element.

13 . The device according to claim 12 , further comprising a plurality of such display elements stacked on top of each other, wherein each of the elements comprises a reflector element having different reflectance wavelength band corresponding to an output wavelength of a narrow-band light source of the projector.

14 . The device according to claim 13 , being a head-up display device or head-mounted display device.

15 . The device according to claim 12 , being a head-up display device or head-mounted display device.

16 . The element according to claim 1 , wherein the reflector element has a total white light transmittance of at least 75%.

17 . The element according to claim 2 , wherein the reflector element comprises a dielectric multilayer structure, having a stack of alternating layers having different indices of refraction.

18 . The element according to claim 3 , wherein the reflector element comprises a dielectric multilayer structure, having a stack of alternating layers having different indices of refraction.

19 . The element according to claim 4 , wherein the reflector element comprises a dielectric multilayer structure, having a stack of alternating layers having different indices of refraction.

20 . The element according to claim 5 , wherein the reflector element comprises a dielectric multilayer structure, having a stack of alternating layers having different indices of refraction.

Assignees

• Dispelix Oy

Inventors

• Olkkonen Juuso
• Sunnari Antti

Classifications

• G02B27/142

  Coating structures, e.g. thin films multilayers · CPC title

• G02B27/0172 Primary

  characterised by optical features · CPC title

• G02B2027/0118

  comprising devices for improving the contrast of the display / brillance control visibility · CPC title

• G02B5/1814

  structurally combined with one or more further optical elements, e.g. lenses, mirrors, prisms or other diffraction gratings (G02B5/189 takes precedence) · CPC title

• G02B27/0101 Primary

  characterised by optical features (G02B27/0172 takes precedence) · CPC title