Image sensing with a waveguide display

• US 10,387,710 B2
• Filed: 09/30/2016
• Issued: 08/20/2019
• Est. Priority Date: 03/07/2016
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Inventors: Chen, Liying, Cheng, Yan
• Primary Examiner(s): Kassa, Yosef
• Application Number:
  US15/282,434
• Publication Number:
  US 20170255813A1
• Time in Patent Office: 1,054 Days
• Field of Search: 382115, 382116, 382124, 382209, 382210, 382278, 382282, 340 553, 340 583
• CPC Class Codes: G02B 5/32 Holograms used as optical elements
• CPC Class Codes: G02B 6/0015 provided on the surface of the light guide or in the bulk of it
• CPC Class Codes: G02B 6/0026 Wavelength selective element, sheet or layer, e.g. filter or grating
• CPC Class Codes: G02B 6/34 utilising prism or grating G02B6/293 takes precedence
• CPC Class Codes: G03H 1/0248 Volume holograms
• CPC Class Codes: G03H 2222/45 Interference beam at recording stage, i.e. following combination of object and reference beams
• CPC Class Codes: G03H 2260/12 Photopolymer
• CPC Class Codes: G06V 40/1312 direct reading, e.g. contactless acquisition
• CPC Class Codes: G06V 40/1324 by using geometrical optics, e.g. using prisms G06V40/1312 takes precedence

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.

Claims

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.