Method and apparatus for contact image sensing

• US 9,727,772 B2
• Filed: 07/30/2014
• Issued: 08/08/2017
• Est. Priority Date: 07/31/2013
• Status: Active Grant

• Current Assignee: DigiLens Inc
• Original Assignee: DigiLens Inc
• Inventors: Popovich, Milan Momcilo, Waldern, Jonathan David
• Primary Examiner(s): Bayat, Ali
• Application Number:
  US14/910,921
• Publication Number:
  US 20160283773A1
• Time in Patent Office: 1,105 Days
• CPC Class Codes: G02B 26/0808 by means of one or more diffracting elements
• CPC Class Codes: G02B 27/4277 being separated by an air space
• 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: G02B 6/0026 Wavelength selective element, sheet or layer, e.g. filter or grating
• CPC Class Codes: G02B 6/0056 for producing polarisation effects, e.g. by a surface with polarizing properties or by an additional polarizing elements
• CPC Class Codes: G02B 6/0076 Stacked arrangements of multiple light guides of the same or different cross-sectional area
• CPC Class Codes: G02B 6/34 utilising prism or grating G02B6/293 takes precedence
• CPC Class Codes: G06V 40/1318 using electro-optical elements or layers, e.g. electroluminescent sensing
• CPC Class Codes: G06V 40/1324 by using geometrical optics, e.g. using prisms G06V40/1312 takes precedence
• CPC Class Codes: H01L 27/14678 Contact-type imagers

Abstract

A contact image sensor having an illumination source; a first SBG array device; a transmission grating; a second SBG array device; a waveguiding layer including a multiplicity of waveguide cores separated by cladding material; an upper clad layer; and a platen. The sensor further includes: an input element for coupling light from the illumination source into the first SBG array; a coupling element for coupling light out of the cores into output optical paths coupled to a detector having at least one photosensitive element.

Claims

1. A contact image sensor comprising:

an illumination source providing a collimated beam of first polarization light;

an illuminator waveguide for propagating light in a first TIR path containing a first array of -grating columns;

a detector comprising at least one photosensitive element;

a platen;

a detector waveguide for propagating light in a second total internal reflection (TIR) path containing a second array of grating columns;

at least one beam steering grating disposed between said platen and said detector waveguide;

a first waveguide coupler for coupling light from said illumination source into said illuminator waveguide; and

,

a second waveguide coupler for coupling light out of said detector waveguide into an output optical path;

wherein each external surface of said detector waveguide is divided into a first grid of strips interspersed with a second grid of strips, said first and second grids having different light-modifying characteristics, overlapping strips from the first grid of strips on each external surface being operative to waveguide light, overlapping strips from the second grid of strips on each external surface being operative to absorb light scattered out of regions of the detector waveguide sandwiched by overlapping strips from the first grid of strips on each external surface, said strips being orthogonal to said grating columns.

2. The apparatus of claim 1 wherein each said grating element in at least one of said first and second grating arrays is switchable between a diffracting state and a non-diffracting state, said switchable grating elements diffracting only said first polarization light.

3. The apparatus of claim 1 wherein the first grid of each said external waveguide surface is one of clear or scattering and the second grid of at least one said external waveguide surface is infrared absorbing.

4. The apparatus of claim 1 wherein in each waveguide said grating columns are orthogonal to said TIR paths.

5. The apparatus of claim 2 wherein said columns in said first and second grating arrays are switched in cyclic fashion with only one said column element in each array being in a diffracting state at any time.

6. The apparatus of claim 1 wherein said first and second TIR paths are parallel.

7. The apparatus of claim 1 wherein said beam steering grating comprises:

a first transmission grating layer;

a half wavelength retarder layer overlaying said first transmission grating layer;

a second transmission grating layer overlaying said half wavelength retarder layer; and

a quarter wavelength retarder layer sandwiched by said second transmission grating layer and said platen.

8. The apparatus of claim 1 wherein external faces of said detector waveguide and said illuminator waveguide abut an air space or a low refractive index material layer.

9. The apparatus of claim 2 wherein said illuminator and detector waveguides each comprise first and second transparent substrates sandwiching said array of grating columns, and transparent electrodes applied to opposing faces of said substrates.

10. The apparatus of claim 2 wherein said grating is one of a forward mode SBG, reverse mode SBG, or stack of thin switchable gratings.

11. The apparatus of claim 2 wherein said diffracting state exists when an electric field is applied across said grating element and said non diffracting states exists when no electric field is applied.

12. The apparatus of claim 2 wherein said diffracting state exists when no electric field is applied across said grating element and said non diffracting states exists when an electric field is applied.

13. The apparatus of claim 2 wherein at any time one element of said first grating array is in a diffracting state, one element of said second grating array is in a diffracting state, all other elements of said first and second grating arrays are in a non-diffracting state.

14. The apparatus of claim 1 wherein said first waveguide coupler couples light from said illumination source into said first TIR path in said illuminator waveguide, wherein an grating element of said illuminator waveguide in a diffracting state diffracts said first TIR path light towards said platen into a first beam direction, wherein said beam steering grating deflects said first beam direction light towards said platen in a second beam direction, wherein when contact is made with an external material at a point on the platen a portion of the second beam direction light incident at the point on the platen contacted by said external material is transmitted out of the platen, wherein light incident on the outer surface of the platen in the absence of said contact with an external material is reflected towards said detector waveguide in a third optical path, wherein a column of said second grating array along said third beam direction diffracts said third angle light into a second TIR path in said detector waveguide;

wherein said second waveguide coupler couples said second TIR path light into an output optical path towards said detector;

wherein said first to third optical paths and said first and second TIR paths are in a common plane.

15. The apparatus of claim 14 wherein said first direction light traverses said detector waveguide.

16. The apparatus of claim 14 wherein said second direction light traverses said illuminator waveguide.

17. The apparatus of claim 2 wherein the output from detector array element is read out in synchronism with the switching of the elements of said first switchable grating array.

19. The apparatus of claim 1 wherein said columns of said first and second switchable grating arrays are switched in cyclic fashion with only one said column element in each array being in a diffracting state at any time.

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

a) providing an apparatus comprising;

an illumination source providing a collimated beam of first polarisation light;

an illuminator waveguide for propagating light in a first TIR beam direction containing a first array of switchable grating columns;

a detector waveguide for propagating light in a first TIR beam direction containing a second array of switchable grating columns, external surfaces of said detector waveguide comprising interspersed multiplicities of strips with different light modifying characteristics, said strips orthogonal to said switchable grating columns, each light modifying strip overlapping a clear strip;

a platen;

a beam steering grating comprising at least one grating disposed between said platen and said detector waveguide;

a first waveguide coupler for coupling light from said illumination source into said illuminator waveguide;

a second waveguide coupler for coupling light out of said detector waveguide into an output optical path; and

a detector comprising at least one photosensitive element;

b) coupling light from said illumination source into said illuminator waveguide;

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

d) sequentially switching elements of said first switchable grating array into a diffracting state, all other elements being in their non-diffracting states;

e) sequentially switching columns of said second switchable grating array into a diffracting state, all other columns being in their non-diffracting states;

f) each diffracting switchable grating element of said first switchable grating array diffracting incident first TIR light upwards into a first optical path;

g) said beam steering grating deflecting said first optical path light into a second optical path;

h) a portion of said second optical path light incident at said point on said platen contacted by said external material being transmitted out of said platen, portions of said second optical path light not incident at said point being reflected into a third optical path;

i) an active switchable grating column element of said second switchable grating array along said third optical path diffracting said third angle light in a second TIR path; and

j) coupling light out of said detector waveguide towards said detector;

wherein said first to third optical paths and said first and second TIR paths are in a common plane.