Patent ID: 6643390
Filing Date: 2003-11-04
Classification: G06K

Abstract:
A biometric fingerprint imaging apparatus comprising:a housing; a platen having a finger receiving surface, mounted in said housing; a light source mounted in said housing providing radiation which is reflected from said finger receiving surface along an optical axis; an image sensor having a plurality of pixels, said image sensor disposed to receive radiation along said optical axis; an optical subsystem which images a square area on said platen finger receiving surface onto a rectangular area on said image sensor to minimize anamorphic, non symmetric distortion, said optical subsystem comprising; a first lens disposed between said finger receiving surface and said image sensor along said optical axis; a second lens disposed between said first lens and said image sensor along said optical axis such that the first lens and second lens form an afocal optical combination; and an aperture stop disposed between said first lens and said second lens to block radiation which does not contribute to an image focused on said plurality of pixels; said apparatus further including an independently controllable bright field light source and a third lens such that sequentially a dark field image and bright field image can be imaged on said sensor.