Coherent optical processor apparatus with improved fourier transform plane spatial filter

• US 3,891,968 A
• Filed: 04/04/1974
• Issued: 06/24/1975
• Est. Priority Date: 04/04/1974
• Status: Expired due to Term

• Current Assignee: Donald H. Mcmahon
• Original Assignee: Donald H. Mcmahon
• Inventors: McMahon, Donald H.
• Primary Examiner(s): Boudreau, Leo H.
• Application Number:
  US05/457,750
• Time in Patent Office: 446 Days
• Field of Search: 340/146.3E,146.3P 350/162SF 356/71 250/237R,236,233,550 178/7.6
• US Class Current: 382/124
• CPC Class Codes: A61B 5/1172 using fingerprinting
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives
• CPC Class Codes: A61B 5/7257 using Fourier transforms
• CPC Class Codes: G06V 10/88 Image or video recognition using optical means, e.g. reference filters, holographic masks, frequency domain filters or spatial domain filters
• CPC Class Codes: G06V 40/1365 Matching; Classification
• CPC Class Codes: G07C 9/37 using biometric data, e.g. fingerprints, iris scans or voice recognition

Abstract

A line pattern or fingerprint ridge pattern identification apparatus employs coherent optical processing techniques wherein the line or ridge orientations and spacings in a plurality of preselected finite areas of the fingerprint are inspected by means of a rotating spatial filterdisposed in the Fourier transform plane of the optical processor for cyclically selecting distinct components of the Fourier transform for transmission to the image plane of the processor in which is disposed a plurality of photodetectors each corresponding to a discrete sampled area of the print. The time delays between a reference orientation of the spatial filter and the blocking and unblocking of light transmitted therethrough toward each photodetector are noted. These values are processed to provide proportional representations thereof for storage and for subsequent comparison with similarly obtained signals representative of ridge line orientation and separation of a fingerprint presented for identification.

Claims

1. 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.

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

3. 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.

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

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

6. 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.

7. 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.

8. 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.

9. 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.

10. 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.

11. 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.

12. 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.

13. 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.

14. 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.