Micromirror optical imager

• US 6,700,606 B1
• Filed: 06/09/1999
• Issued: 03/02/2004
• Est. Priority Date: 06/09/1999
• Status: Expired due to Term

• Current Assignee: Activcard Ireland, Limited (Assa Abloy AB)
• Original Assignee: Activcard Ireland, Limited (Assa Abloy AB)
• Inventors: Borza, Stephen J.
• Primary Examiner(s): Le, Vu
• Assistant Examiner(s): MISLEH, JUSTIN P
• Application Number:
  US09/328,345
• Time in Patent Office: 1,728 Days
• Field of Search: 348/218.1, 348/344, 348/335, 348/340, 382/124, 382/126, 382/127, 382/125, 359/223, 359/224, 359/212, 359/95
• US Class Current: 348/218.1
• CPC Class Codes: G06V 40/13 Sensors therefor
• CPC Class Codes: H04N 23/58 Means for changing the camera field of view without moving the camera body, e.g. nutating or panning of optics or image sensors

Abstract

An optical imaging device such as a fingerprint imager is disclosed that has an array of micromirrors that allows sequential scanning of areas of a platen in steps. The scanned areas of the platen are transmitted to an image sensor and a composite image constructed from the scanned areas. By transmitting scanned areas of the platen in sections, the image sensor area required is reduced in contrast to prior art optical images that scan the whole platen in a single step.

Claims

1. An optical imager comprising:

a light source for emitting light;

a platen for reflecting a portion of light emitted by the light source and incident thereon;

an image sensor for sensing light incident thereon; and

,

a micromirror device operable from a first reflecting position for reflecting a first portion of light reflected from a first location on the platen along a first optical path from the platen to the image sensor to a second other reflecting position for reflecting a second portion of light reflected from a second other location on the platen along a second optical path from the platen to the image sensor.

2. An optical imager according to claim 1, comprising:

a controller for moving the micromirror device between the first reflecting position and the second reflecting position.

3. An optical imager according to claim 2,

wherein the micromirror device comprises an array of micromirrors.

4. An optical imager according to claim 3,

wherein within each of the first optical path and the second optical path is disposed a lens for focusing light onto the imager.

5. An optical imager according to claim 4,

wherein the image sensor comprises a charge coupled device.

6. An optical imager according to claim 1,

wherein the micromirror device is operable in a third other reflecting position.

7. An optical imager according to claim 1,

wherein the micromirror device comprises a multi-stable Digital Micromirror Device.

8. An optical imager according to claim 1, comprising:

a processor for combining captured image data to form a composite image therefrom.

9. A method of capturing an image comprising the steps of:

positioning an array of micromirrors in a first reflective position;

acquiring a first image of light reflected from the array of micromirrors to form an image of a first area;

positioning the micromirrors in a second other reflective position;

acquiring a second image of light reflected from the array of micromirrors to form an image of a second area; and

,

combining the first image and the second image to form a composite image of an area larger than the first area and larger than the second area.

10. A method of capturing an image according to claim 9, comprising the steps of:

positioning an array of micromirrors in a third reflective position; and

,

acquiring a third image of light reflected from the array of micromirrors to form an image of a third area,

wherein during the step of combining, the third image is combined with the first and second images.

11. A method of capturing an image according to claim 9, comprising the step of:

correlating portions of the first image and the second image to determine a portion common to the first image and the second image, the determination used in combining the images to form a composite image.

12. A method of imaging a fingerprint according to claim 9, comprising the steps of:

determining if the first image includes biometric information and providing a result based on the determination; and

,

when the result is indicative of a presence of biometric information performing the step of positioning the micromirrors in the second other reflective position.

13. A method of capturing an image comprising the steps of:

positioning an array of micromirrors in a first reflective position;

acquiring a first image of light reflected from the array of micromirrors to form an image of a first area;

moving the micromirrors to a second other reflective position;

during motion of the micromirrors at intervals acquiring a plurality of images of light reflected from the array of micromirrors to form an image of a other areas; and

,

combining the first image and the plurality of images to form a composite image.

14. A method of capturing an image as defined in claim 13,

wherein the step of combining images is performed in dependence upon a known image capture rate relative to a rate of motion of the micromirrors.

15. A method of capturing an image as defined in claim 13,

wherein the step of combining images is performed in dependence upon a sensed micromirror position associated with some captured images from the plurality of captured images.

16. A method of capturing an image as defined in claim 13 comprising the step of:

when the micromirrors are in the second other reflective position, capturing a second other image of light reflected from the array of micromirrors to form an image of a second area;

wherein the step of combining images combines images including the second other image.

17. A method of capturing an image as defined in claim 13,

wherein the step of combining images is performed in dependence upon known information relating to micromirror motion and image analysis to determine portions of images that overlap.