Method and apparatus for contact image sensing
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.
1. A light sensor incorporating a waveguide device comprising:
a detector;
a first coupler configured to direct light reflected off an object into a waveguide device;
a second coupler configured to direct light propagating within said waveguide device onto the detector;
an optical substrate with first and second light reflecting surfaces; and
plurality of light absorbing regions on at least one of said surfaces, each light absorbing region bordering at least one non-absorbing region;
wherein each said non-absorbing region of said first surface overlaps with a non-absorbing region of said second surface forming a plurality of waveguiding channels within a waveguiding volume within said substrate such that each waveguiding channel is capable of propagating a light beam without crossing over into an adjacent waveguiding channel.
2. The apparatus of claim 1 , wherein said non-absorbing regions are portions of said substrate surface at which total internal refection can take place.
3. The apparatus of claim 1 further comprising a portion of the at least one non-absorbing region that is textured on the light reflecting surface to scatter light or coated to provide partial reflection of light.
4. The apparatus of claim 1 , further comprising a source of light optically coupled to said waveguide, wherein light from said source is transmitted through said waveguide onto said object.
5. The apparatus of claim 4 , wherein said light is collimated before being coupled into said waveguide.
6. The apparatus of claim 4 , wherein said source emits infrared or ultraviolet radiation.
7. The apparatus of claim 4 , wherein said light is polarized before being coupled into said waveguide.
8. The apparatus of claim 4 , further comprising at least one of a polarization selection layer, a polarization rotation layer, a switching grating, a platen for contact image formation, a transparent substrate, a layer of air, a layer of low index material, or a grating layer, which is disposed along a light path from said object to said detector.
9. The apparatus of claim 1 , wherein said first coupler includes a grating layer for coupling light reflected from said object into total internal reflection paths within said plurality of channels.
10. The apparatus of claim 9 , wherein said grating layer is one of a transmission grating or a reflection grating implemented as one of a forward mode switchable Bragg grating, a reverse mode switchable Bragg grating, a stack of thin switchable gratings or a surface relief grating.
11. The apparatus of claim 9 , wherein said grating layer at least partially overlaps said waveguiding volume.
12. The apparatus of claim 9 , wherein said grating layer is patterned into a multiplicity of elongate grating elements aligned orthogonal to a light propagation direction of said waveguiding volume.
13. The apparatus of claim 9 , wherein said optical substrate is divided into a pair of substrates sandwiching said grating, and transparent electrodes are applied to a surface of each substrate.
14. The apparatus of claim 9 , wherein said grating layer includes a plurality of grating elements switchable between a diffracting state and a non-diffracting state, wherein said grating elements are switched sequentially.
15. The apparatus of claim 9 , wherein said optical substrate is divided into a pair of substrates sandwiching said grating.
16. The apparatus of claim 1 , wherein said light absorbing regions and said non-absorbing regions form a grid of strips patterned such that multiple parallel waveguiding channels are formed.
17. The apparatus of claim 1 , wherein external faces of said waveguide abut air or a low refractive index material layer.
18. The apparatus of claim 1 , wherein said first coupler is one of: a grating or a prism, and said second coupler is one of: a grating or a prism.
19. The apparatus of claim 1 , wherein said substrate contains waveguiding cores, each said core overlapped by at least one non-absorbing region of said substrate surfaces.
20. The apparatus of claim 1 , wherein said detector comprises at least one photoconductive element optically coupled to a waveguiding channel.
21. The apparatus of claim 1 , wherein each light absorbing region is formed by a light absorbing coating disposed on the at least one of said surfaces.