Coherent optical processor apparatus with improved fourier transform plane spatial filter

Claim 2

An optical processor fingerprint inspection apparatus comprising: optical means for generating a diffraction pattern of the fingerprint to be identified in the Fourier transform plane of said inspection apparatus, opaque Mask means having at least one internal asymmetric transparent portion disposed fully within said mask means in said Fourier transform plane, said internal asymmetric transparent portion having a radially disposed internal boundary edge cooperating with a curvate internal boundary edge for the cyclic control of the passage of light therethrough, means for cyclically rotating said internal asymmetric transparent portion about the major axis of said optical means through said diffraction pattern, means responsive to radiant energy transmitted cyclically through said transparent portion between said radial and curvate internal boundary edges during passage thereof through said diffraction pattern for sensing the amplitude of ridge line separation of said fingerprint.

Claim 3

Apparatus as described in claim 1 wherein said radially disposed internal boundary edge is substantially straight.

Claim 4

Apparatus as described in claim 2 wherein the locus of said curvate internal boundary edge is substantially a monotonic function of its radial position versus angle of rotation of said internal asymmetric transparent portion.

Claim 5

Apparatus as described in claim 2 wherein said curvate internal boundary edge is substantially a sector of a spiral.

Claim 6

Apparatus as described in claim 2 wherein said curvate internal boundary edge is substantially a sector of a circle.

Claim 7

Apparatus as described in claim 2 wherein said optical means comprises: means for illuminating a fingerprint to be inspected with a coherent optical beam to produce a spatially modulated beam representative of said fingerprint, and means for focussing said modulated beam to produce said diffraction pattern at said Fourier transform plane.

Claim 8

Apparatus as described in claim 6 further including means oriented for receiving light transmitted through said opaque mask means internal asymmetric transparent portion for forming an image in the plane of said means for sensing radiant energy.

Claim 9

Apparatus as described in claim 7 further including a plurality of light detectors positioned in said image plane each at a discrete location and corresponding to a respective finite sample area of the fingerprint to be inspected.

Claim 10

Apparatus as described in claim 8 wherein said opaque mask means is disposed in said Fourier transform plane for scanning said diffraction pattern to control the transmission of light to said respective light detectors sequentially in accordance with the orientation and separation of the ridge lines of the related sample areas.

Claim 11

Apparatus as described in claim 9 further including means for differentiating the outputs of said respective light detectors for generating sequential signals of first and second polarities.

Claim 12

An optical processor fingerprint inspection apparatus comprising: optical means for generating a diffraction pattern of the fingerprint to be identified in the Fourier transform plane of said inspection apparatus and including: means for illuminating a fingerprint to be inspected with a coherent optical beam to produce a spatially modulated beam representative of said fingerprint, and means for focussing said modulated beam to produce said diffraction pattern at said Fourier transform plane, opaque mask means having at least one transparent portion and disposed in said Fourier transform plane, said transparent portion having a radially disposed staight boundary edge cooperating with a curvate boundary edge, means for rotating said transparent portion about the major axis of said optical means, means oriented for receiving light transmitted through said opaque mask means transparent portion for forming an image in the plane of means for sensing radiant energy, means responsive to said means for sensing radiant energy transmitted through said transparent portion for sensing the amplitude of ridge line separation of said fingerprint including: a plurality of light detectors positioned in said image plane at a discRete location and corresponding to a respective finite sample area of the fingerprint to be inspected, said opaque mask means being disposed in said Fourier transform plane for scanning said diffraction pattern to control the transmisson of light to said respective light detectors sequentially in accordance with the orientation and separation of the ridge lines of the related sample areas, means for differentiating the outputs of said respective light detectors for generating sequential signals of first and second polarities, and means for determining a first time interval between a predetermined time reference and the instant of said first polarity signal.

Claim 13

An optical processor fingerprint inspection apparatus comprising: optical means for generating a diffraction pattern of the fingerprint to be identified in the Fourier transform plane of said inspection apparatus and including: means for illuminating a fingerprint to be inspected with a coherent optical beam to produce a spatially modulated beam representative of said fingerprint, and means for focussing said modulated beam to produce said diffraction pattern at said Fourier transform plane, opaque mask means having at least one transparent portion and disposed in said Fourier transform plane, said transparent portion having a radially disposed staight boundary edge cooperating with a curvate boundary edge, means for rotating said transparent portion about the major axis of said optical means, means oriented for receiving light transmitted through said opaque mask means transparent portion for forming an image in the plane of means for sensing radiant energy, means responsive to said means for sensing radiant energy transmitted through said transparent portion for sensing the amplitude of ridge line separation of said fingerprint including: a plurality of light detectors positioned in said image plane at a discRete location and corresponding to a respective finite sample area of the fingerprint to be inspected, said opaque mask means being disposed in said Fourier transform plane for scanning said diffraction pattern to control the transmisson of light to said respective light detectors sequentially in accordance with the orientation and separation of the ridge lines of the related sample areas, means for differentiating the outputs of said respective light detectors for generating sequential signals of first and second polarities, and means for determining a first time interval between a predetermined time reference and the instant of said first polarity signal.

Claim 14

Apparatus as described in claim 11 further including means for determining a second time interval between said predetermined time reference and the instant of said second polarity signal.

Claim 15

Apparatus as described in claim 12 further including subtractive means for determining a third time interval representative of the difference between said first and second time intervals.

Claim 16

Apparatus as described in claim 11 wherein said time interval determining means includes: a counter, means for resetting said counter at a predetermined scanning position of said internal asymmetric transparent portion, means for generating time pulses for application to said counter for generating timing counts, and means for storing said timing count when corresponding to the interval between the instant of reset and the instant of generation of at least one of said first and second polarity signals.