Contact image sensor using switchable Bragg gratings
First Claim
1. A contact image sensor comprising:
- a light source providing a collimated beam;
a platen;
a first array of switchable grating elements disposed in a layer for coupling light from said source towards said platen;
a plurality of detector elements spatially distributed in two dimensions;
a plurality of waveguiding cores disposed in a layer; and
a second array of switchable grating elements disposed in a layer for coupling light reflected from said platen into a TIR path to said detector elements via said plurality of waveguiding cores,wherein each waveguiding core transmits light to a unique detector element;
wherein the contact image sensor is configured to perform a sequence of switching steps, wherein in each step one grating element of said first array of switchable grating elements and one element of said second array of switchable grating elements are switched into their diffracting states with all other grating elements remaining in their non-diffracting states.
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Abstract
A contact image sensor comprises: a light source providing a collimated beam; a detector and a switchable grating array comprising first and second transparent substrates sandwiching an array of switchable grating elements with transparent electrodes applied to said substrates, said substrates together providing a total internal reflection light guide. A first transmission grating layer overlays said first substrate. A second transmission grating layer overlays said second substrate. A quarter wavelength retarder layer overlays said second transmission grating layer. A platen overlays said quarter wavelength retarder layer; a polarization-rotating reflecting layer overlaying said first transmission grating layer. An input coupler for directing light from said light source into said light guide and an output coupler for extracting light out of said light guide towards said detector are also provided.
800 Citations
20 Claims
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1. A contact image sensor comprising:
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a light source providing a collimated beam; a platen; a first array of switchable grating elements disposed in a layer for coupling light from said source towards said platen; a plurality of detector elements spatially distributed in two dimensions; a plurality of waveguiding cores disposed in a layer; and a second array of switchable grating elements disposed in a layer for coupling light reflected from said platen into a TIR path to said detector elements via said plurality of waveguiding cores, wherein each waveguiding core transmits light to a unique detector element; wherein the contact image sensor is configured to perform a sequence of switching steps, wherein in each step one grating element of said first array of switchable grating elements and one element of said second array of switchable grating elements are switched into their diffracting states with all other grating elements remaining in their non-diffracting states. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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20. A method of making a contact image measurement, comprising the steps of:
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a) providing an apparatus comprising;
a light source providing a collimated beam;
a platen;
a plurality of detector elements spatially distributed over two dimensions;
a plurality of waveguiding cores disposed in a layer;
a first array of switchable grating elements for coupling light from said source towards said platen; and
a second array of switchable grating elements for coupling light reflected from said platen into a TIR path to said detector elements;
each said waveguide core overlaying a unique detector element;b) coupling light from said source into a total internal reflection path in said first array of switchable grating elements; c) switching one grating element in each of said first and second arrays of switchable grating elements into their diffracting state with all other elements remaining in their non-diffracting states; d) diffracting said light towards said platen via said first array of switchable grating elements; e) transmitting light incident on a region of an external surface of said platen in contact with an external material and reflecting light not incident on said region from said external surface; f) coupling light reflected from said platen into said plurality of waveguiding cores via at least one element of said second array of switchable grating elements in said diffracting state; g) coupling said light out of said plurality of waveguide cores onto said detector elements; h) repeating steps c) to g) with different pairs of switchable grating elements being switched into their diffracting states.
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Specification