Patent ID: 7580550
Filing Date: 2009-08-25
Classification: G02B,G06K

Abstract:
1. An optical device for forming an image of fingerprints, comprising: an optical plate with: a first main face constituting a face for affixing a finger of which an image of the fingerprints is to be obtained, a first lateral face arranged as a convergent mirror, and a second lateral face, opposite the first lateral face and forming an exit face of the optical plate which defines an angle greater than 90° with said first main face, at least one light source for illuminating said first main face through the optical plate, a focusing objective located opposite said exit face, said focusing objective having an object focal point situated substantially in a focal plane of said convergent mirror, and a diaphragm provided with an aperture, said diaphragm being interposed between said exit face and said focusing objective and situated substantially in the vicinity to said focusing objective, wherein a plane defined by said first main face defines an angle between 2° and 25° with a plane perpendicular to said exit face and intersects said diaphragm under and in the vicinity to said aperture thereof, whereby the angle of incidence of the light rays on said first main face, inside the optical plate, is increased and the stray light transmitted from said exit face is substantially intercepted by said diaphragm under said aperture thereof, while the thickness of the optical plate can be reduced.