Image sensing with a waveguide display

Patent metadata

Field	Value
Publication number	US-10387710-B2
Application number	US-201615282434-A
Country	US
Kind code	B2
Filing date	Sep 30, 2016
Priority date	Mar 7, 2016
Publication date	Aug 20, 2019
Grant date	Aug 20, 2019

Abstract

An electronic device includes an image sensing display. The display includes a cover glass and is configured as a waveguide. A volume holographic grating in the display diffracts incident light from an object positioned outside the display. The diffracted incident light has an angle of incidence relative to the volume holographic grating that satisfies the Bragg condition. The volume holographic grating diffracts the incident light through the waveguide at a predetermined angle and with a predetermined waveguide exit distance to focus at the image sensor. An image sensor is positioned at an output of the waveguide to capture the diffracted incident light propagated through the waveguide. Image processing circuitry is coupled to the image sensor to recognize a fingerprint image captured by the image sensor through the waveguide.

First claim

What is claimed is:

1. An imaging system comprising:
a display configured as a waveguide, the display including a cover glass and a volume holographic grating configured to diffract incident light from an object positioned outside the display, the diffracted incident light having an angle of incidence relative to the volume holographic grating that satisfies the Bragg condition, the volume holographic grating diffracting the incident light through the waveguide at a predetermined angle.

2. The imaging system of claim 1 further comprising:
an image sensor positioned at an output of the waveguide to capture the diffracted incident light propagated through the waveguide.

3. The imaging system of claim 1 wherein the display further includes a transparent or translucent substrate adjacent to the volume holographic grating.

4. The imaging system of claim 1 wherein the volume holographic grating selectively diffracts incident light having a normal angle of incidence with the volume holographic grating for transmission through the waveguide.

5. The imaging system of claim 1 wherein the volume holographic grating selectively diffracts incident light converging to the volume holographic grating for transmission through the waveguide.

6. The imaging system of claim 1 wherein the incident light is reflected from a feature of the object that is not in contact with the display.

7. The imaging system of claim 1 wherein angular selectivity in diffraction of incident light into the waveguide is set during manufacturing by the angle of incidence of an object light relative to a reference light, the reference light having a normal angle of incidence at the volume holographic grating.

8. The imaging system of claim 1 wherein a waveguide exit distance of the diffracted light is set during manufacturing by an offset between an objective lens passing the object light to the volume holographic grating and a side of the volume holographic grating on which the reference light impinges during manufacturing.

9. The imaging system of claim 2 further comprising:
image processing circuitry coupled to the image sensor and configured to recognize a fingerprint image captured by the image sensor through the waveguide.

10. A method comprising:
diffracting, via a volume holographic grating, incident light from an object positioned outside a display, the display being configured as a waveguide, the diffracted incident light having an angle of incidence relative to the volume holographic grating that satisfies the Bragg condition; and
propagating the diffracted incident light through the waveguide at a predetermined angle.

11. The method of claim 10 further comprising:
capturing the diffracted incident light propagated through the waveguide at an output of the waveguide.

12. The method of claim 10 wherein the display includes a cover glass and a transparent or translucent substrate adjacent to the volume holographic grating.

13. The method of claim 10 wherein the volume holographic grating selectively diffracts incident light having a normal angle of incidence with the volume holographic grating for transmission through the waveguide.

14. The method of claim 10 wherein the volume holographic grating selectively diffracts incident light converging to the volume holographic grating for transmission through the waveguide.

15. The method of claim 10 wherein the incident light is reflected from a feature of the object that is not in contact with the display.

16. The method of claim 10 further comprising:
setting angular selectivity in diffraction of incident light into the waveguide during manufacturing based on an angle of incidence of an object light relative to a reference light, the reference light having a normal angle of incidence at the volume holographic grating.

17. The method of claim 10 further comprising:
setting the waveguide exit distance of the diffracted incident light during manufacturing by an offset between an objective lens passing the object light to the volume holographic grating and a side of the volume holographic grating on which the reference light impinges during manufacturing.

18. The method of claim 10 further comprising:
capturing an image of a fingerprint from the diffracted incident light propagated through the waveguide at the output of the waveguide; and
recognizing the fingerprint image captured by an image sensor through the waveguide.

19. An electronic device comprising:
a cover glass;
a display panel layer;
a volume holographic grating configured to diffract incident light from an object positioned outside the display through a waveguide including the cover glass, the object being illuminated through the cover glass from the direction of the display panel layer, the diffracted incident light having an angle of incidence relative to the volume holographic grating that satisfies the Bragg condition, the volume holographic grating diffracting the incident light through the waveguide at a predetermined angle; and
an image sensor positioned at an output of the waveguide to capture the diffracted incident light propagated through the waveguide.

20. The electronic device of claim 19 further comprising:
image processing circuitry coupled to the image sensor and configured to recognize a fingerprint image captured by the image sensor through the waveguide.

Assignees

• Microsoft Technology Licensing Llc

Inventors

• Chen Liying
• Cheng Yan

Classifications

• G02B5/32

  Holograms used as optical elements · CPC title

• G02B6/0026

  Wavelength selective element, sheet or layer, e.g. filter or grating · CPC title

• G02B6/0015

  provided on the surface of the light guide or in the bulk of it · CPC title

• G03H2260/12

  Photopolymer · CPC title

• G03H2222/45

  Interference beam at recording stage, i.e. following combination of object and reference beams · CPC title