METHOD AND APPARATUS FOR CONTACT IMAGE SENSING

• US 20180074352A1
• Filed: 03/30/2016
• Published: 03/15/2018
• Est. Priority Date: 03/31/2015
• Status: Active Grant

• Current Assignee: DigiLens Inc
• Original Assignee: DigiLens Inc
• Inventors: POPOVICH, Milan Momcilo, WALDERN, Jonathan David, GRANT, Alastair John
• Granted Patent: US 10,591,756 B2
• Time in Patent Office: Days
• CPC Class Codes: G02B 26/0808 by means of one or more diffracting elements
• CPC Class Codes: G02B 27/4272 having plural diffractive elements positioned sequentially along the optical path
• CPC Class Codes: G02B 5/1828 having means for producing variable diffraction controlling the direction of light by means of one or more diffracting elements G02B26/0808; acousto-optical elements G02F1/11, G02F1/33; electro- or magneto-optical diffraction G02F1/292, G02F1/2955
• CPC Class Codes: G02F 1/1326 Liquid crystal optical waveguides or liquid crystal cells specially adapted for gating or modulating between optical waveguides
• CPC Class Codes: G02F 1/29 for the control of the position or the direction of light beams, i.e. deflection

Abstract

A contact image sensor having a waveguiding structure for propagating light in a first direction including, in series, a first clad medium, a first core, a switchable grating clad, a second core, and a second clad medium sandwiched by transparent substrates, patterned parallel electrode elements orthogonally traversing the waveguides, a light source, a platen and a detector. Switchable grating regions overlapped by a first voltage-addressed electrode element diffract TIR light from the first core towards the platen. Switchable grating region overlapped by a second voltage-addressed electrode element diffract TIR light reflected from the platen into a TIR path within the second core.

Claims

1. A contact image sensor comprising:

a waveguiding structure for propagating light in a first direction comprising, in series disposed in a layer sandwiched by transparent substrates, a first clad medium, a first core, a switchable grating clad, a second core, and a second clad medium;

electrodes applied to opposing surfaces of said substrates at least one patterned into a set of parallel elements orthogonally traversing said cores;

to a light source optically coupled to said first and second cores;

a platen in optical contact with said waveguiding structure;

a detector optically coupled to said first and second core regions;

wherein switchable grating regions overlapped by a first voltage-addressed electrode element are operative, in their diffracting state, to diffract TIR light from first core into a path to outer surface of said platen,

wherein switchable gratings region overlapped by a second voltage-addressed electrode element are operative, in their diffracting state, to diffract TIR light reflected from said platen into a TIR path to said detector along said second core.

2. The apparatus of claim 1 wherein said waveguiding structure comprises a multiplicity of said cores and said clads cyclically arranged.

3. The apparatus of claim 1 wherein said voltages are applied sequentially, two electrodes at a time, to all electrodes in the array.

4. The apparatus of claim 1 wherein said diffracting state exists when no electric field is applied across said SBG element and said non-diffracting state exists when an electric field is applied or said diffracting state exists when an electric field is applied across said SBG element and said non-diffracting state exists when no electric field is applied.

5. The apparatus of claim 1 wherein when contact is made with an external material at a region on said platen a portion of the light incident at the region on said platen contacted by said external material is transmitted out of said platen, wherein light incident on the outer surface of said platen in the absence of said contact with an external material is reflected downwards.

6. The apparatus of claim 1 wherein when contact is made with an external material at a region on said platen a portion of the light incident at the region on said platen contacted by said external material is reflected downwards, wherein light incident on the outer surface of said platen in the absence of said contact with an external material. is transmitted out of said platen.

7. The apparatus of claim 1 wherein the output from said detector is read out in synchronism with the switching of said electrode elements.

8. The apparatus of claim 1 wherein said light source is one of a laser or LED and said light is coupled into said waveguiding structure by one of a grating or a prism.

9. The apparatus of claim 1 wherein said grating or prism are clocked.

10. The apparatus of claim 1 wherein said switchable grating clad is a switchable Bragg grating recorded in one of a HPDLC grating, uniform modulation grating or reverse mode HPDLC grating.

11. The apparatus of claim 1 wherein said switchable grating clad includes at least one of a fold grating or a multiplexed grating or a rolled k-vector grating.

19. The apparatus of claim 1 wherein the output from detector is read out in synchronism with the switching of the electrode elements.

20. The apparatus of claim 1 configured as a finger print scanner or a touch sensor.

12. A method of making a contact image measurement comprising the steps of:

a) providing a waveguiding structure for propagating light in a first direction comprising, in series disposed in a layer sandwiched by transparent substrates, a first clad medium, a first core, a switchable grating clad, a second core, and a second clad medium;

electrodes applied to opposing surfaces of said substrates at least one patterned into a set of parallel elements orthogonally traversing said cores;

a light source optically coupled to said first and second cores;

a platen in optical contact with said waveguiding structure;

a detector optically coupled to said first and second core regions;

b) coupling said light into a TIR path in said waveguiding structure;

c) an external material contacting a region on the external surface of said platen;

d) setting first and second electrode elements to a first voltage state and all other voltage-addressed electrodes set to a second voltage state;

e) switchable grating regions overlapped by a first electrode element diffracting TIR light from first core into a path to the platen outer surface;

f) switchable grating regions overlapped by a second electrode element diffracting light reflected from one of said region or said platen external surface into a TIR path in said second core;

g) transmitting said reflected light to said detector.

13. The method of claim 12 wherein said first voltage state corresponds to a voltage being applied and said second voltage state corresponds to no voltage being applied.

14. The method of claim 12 wherein said first voltage state corresponds to no voltage being applied and said second voltage state corresponds to a voltage being applied.

15. The method of claim 12 wherein at least a portion of said light incident at said region on said platen is transmitted out of said platen, wherein at least a portion of said second optical path light not incident at said region is reflected.

16. The method of claim 12 wherein at least a portion of said light incident at said region on said platen is reflected, wherein at least a portion of said second optical path light not incident at said region being transmitted out of said platen.

17. The apparatus of claim 12 wherein said waveguiding structure comprises a multiplicity of said cores and said clads cyclically arranged.

18. The apparatus of claim 12 wherein said voltages are applied sequentially, two electrodes at a time, to all electrodes in the array.