Optical imaging device

• US 5,920,384 A
• Filed: 12/09/1997
• Issued: 07/06/1999
• Est. Priority Date: 12/09/1997
• Status: Expired due to Term

• Current Assignee: Activcard Ireland, Limited (Assa Abloy AB)
• Original Assignee: DEW Engineering and Development Limited (Trelleborg AB)
• Inventors: Borza, Stephen J.
• Primary Examiner(s): Rosenberger, Richard A.
• Application Number:
  US08/986,939
• Time in Patent Office: 574 Days
• Field of Search: 356/71, 382/124, 382/126, 382/127
• US Class Current: 356/71
• CPC Class Codes: G06V 40/1324 by using geometrical optics, e.g. using prisms G06V40/1312 takes precedence
• CPC Class Codes: G07C 9/37 using biometric data, e.g. fingerprints, iris scans or voice recognition

Abstract

An optical imaging device such as a fingerprint imager has a platen formed of a plurality of parallel prisms and a light source for illuminating a portion of the platen. An optical sensor is disposed so as to receive light from the light source reflected off a surface of the platen and directed toward the optical sensor. The platen is mounted moveable relative to the sensor so as to allow scanning of a fingertip in contact with the platen during relative motion of the platen and the sensor. Preferably, the platen is formed of a microprism structure.

Claims

1. A biometric imaging device comprising:

an optical sensor for detecting incident light and for providing a second signal in dependence upon incident light, the optical sensor having an optical sensor rate for capturing a predetermined area;

a light source for providing light to the optical sensor along an optical path;

a platen comprising a plurality of prisms, the platen disposed within the optical path for reflecting a portion of light incident thereon along the optical path toward the optical sensor;

wherein at least one of the optical path and the platen is moveable relative to the other to provide relative movement independent of the optical sensor rate; and

,

a motion sensor for sensing relative motion between the platen and the optical path and for providing a first signal in dependence thereon.

2. A biometric imaging device according to claim 1 comprising a processor for receiving the first signal and the second signal and for providing a third signal based on the first signal and the second signal the third signal comprising image data and a relative location for the image data.

3. A biometric imaging device according to claim 1 comprising a processor for receiving the second signal and for determining a substantial likelihood of a presence of a fingertip on the platen.

4. A biometric imaging device according to claim 1 wherein the optical sensor comprises a linear array of optical sensors for capturing a scan line;

wherein the platen comprises a microprism structure; and

comprising a processor for determining a location of a captured scan line and for performing one of providing the scan line with further data indicative of the location and storing the scan line at a memory address based on the location.

5. A biometric imaging device comprising:

i) a moveable platen having a first surface for accepting a biometric information source on one side thereof and a plurality of substantially parallel prisms having a face parallel to the first surface and illumination and viewing faces on a second side of the platen;

ii) a motion sensor for sensing movement of the movable platen and for providing a first signal in dependence thereon;

iii) a source of light for directing light through an illumination face of a prism from the plurality of prisms and for illuminating a portion of the first surface; and

,

iv) an image sensor for receiving light reflected from the first surface through a viewing face of a prism from the plurality of prisms and for providing a second signal in dependence upon received light, the image sensor having a sensor rate for capturing a predetermined area and the movable platen being capable of motion at a speed independent of the sensor rate for capturing a predetermined area.

6. A biometric imaging device as defined in claim 5 wherein the first face of the prisms are substantially the platen surface.

7. A biometric device as defined in claim 5 wherein the illumination faces are substantially parallel one to the others and viewing faces are substantially parallel one to the others.

8. A biometric imaging device as defined in claim 5 wherein the platen comprises a microprism structure.

9. A biometric imaging device as defined in claim 5 comprising a processor for receiving the first signal and the second signal and for providing a third signal based on the first and second signals the third signal comprising image data and a relative location for the image data.

10. A biometric imaging device as defined in claim 5 comprising a second optical path and a further image sensor disposed to receive light reflected off the platen along the second optical path.

11. A method of capturing biometric information comprising the steps of:

a) providing a biometric information source;

b) capturing a scan line across the biometric information source with an image sensor;

c) measuring a scan line location using a motion sensor;

d) storing the captured scan line in memory;

e) moving the biometric information source relative to the image sensor;

f) detecting the relative motion and determining a distance therefrom;

g) capturing another scan line across the biometric information source with the image sensor;

h) storing in a non-sequential fashion the captured other scan line in memory in dependence upon the detected relative motion; and

,

i) repeating the steps (e), (f), (g), and (h) a plurality of times.

12. A method of capturing biometric information according to claim 11 wherein the steps (e), (f), (g), and (h) are repeated until substantially an entire image of the biometric information source is captured and stored.

13. A method of capturing biometric information according to claim 11 further comprising the step of analysing the scan line to determine a presence of biometric information within the scan line.

14. A method of capturing biometric information according to claim 11 wherein the step of e) moving the biometric information source relative to the image sensor is performed by moving the platen and the biometric information source disposed upon the platen.

15. A method of capturing biometric information according to claim 11 wherein the step of (h) storing the captured other scan line in memory in dependence upon the detected relative motion is performed by storing a scan line at a memory address based on the detected relative motion and an image resolution.

16. A method of capturing biometric information according to claim 11 comprising the step of maintaining information relating to one of locations of scan lines that are captured and stored in a present image and locations of scan lines that are not captured and stored in a present image.

17. A fingerprint imaging device comprising:

a linear photodetector array for detecting incident light and for providing a second signal in dependence upon incident light;

a light source for providing light to the linear photodetector array along an optical path;

a microprism structure disposed with a substantially flat side thereof for receiving a fingertip and with a portion of the other side thereof within the optical path for receiving light from the light source and for reflecting a portion of light incident thereon along the optical path toward the optical photodetector array, the microprism structure moveably mounted to permit movement along a direction substantially parallel to the substantially flat side thereof;

a motion sensor for sensing relative motion between the platen and the optical path and for providing a first signal in dependence thereon; and

,

a processor for storing image information in a non-sequential fashion based on the first and second signals;

whereby an entire image of a fingerprint is captured by detecting incident light at each of a plurality of different relative locations and by storing information relating to the detected incident light at each different location.