Compact optical fingerprint sensor and method

• US 6,750,955 B1
• Filed: 03/14/2002
• Issued: 06/15/2004
• Est. Priority Date: 03/14/2002
• Status: Expired due to Term

• Current Assignee: LF Capital Partners, LLC
• Original Assignee: I.C. Media Corporation
• Inventors: Feng, Chen
• Primary Examiner(s): Font, Frank G.
• Assistant Examiner(s): Punnoose, Roy M.
• Application Number:
  US10/100,689
• Time in Patent Office: 824 Days
• Field of Search: 356/71, 382/116, 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

Abstract

For use in capturing a fingerprint image, an optical fingerprint sensor. In one embodiment of the present invention, the optical fingerprint sensor includes: (1) a light source on a PCB assembly, (2) a diffuser that receives light from the light source, (3) a right angle prism that receives light from the diffuser, (4) a collimating lens that receives light from the prism, (5) a first mirror that receives light from the collimating lens, (6) a second mirror that receives light from the first mirror, (7) a third mirror that receives light from the second mirror, (8) an imaging lens that receives light from the third mirror, and (9) an image sensor on the same PCB assembly as the light source that receives light from the imaging lens.

Claims

1. An optical fingerprint sensor, comprising:

a diffuser for receiving the plurality of light rays and collimating the plurality of light rays to the prism;

a prism for receiving a plurality of light rays, the prism reflecting the light rays when a finger surface is in contact with the upper surface of the prism;

a first mirror for receiving the light rays and for reflecting the plurality of light rays from the prism;

a collimating lens, coupled between the prism and the first mirror, for receiving the plurality of light rays from the prism and for focusing the plurality of light rays to the first mirror;

a second mirror for receiving the plurality of light rays from the first mirror and for reflecting the plurality of light rays; and

an imaging lens for receiving the plurality of light rays from the second mirror and focusing the plurality of light rays onto a sensor.

2. The optical fingerprint sensor of claim 1, further comprising a third mirror, coupled between the second mirror and the imaging lens, for receiving the plurality of light rays form the second mirror and for reflecting the plurality of light rays to the imaging lens.

3. A method for imaging a fingerprint, comprising:

receiving a plurality of light rays by a diffuser;

reflecting the plurality of light rays at a top surface of a prism, comprising;

if a finger surface is present at the top surface of the prism, absorbing the plurality of light rays by the finger that impinges the top surface of the prism; and

if a finger surface is not present at the top surface of the prism, reflecting the plurality of light rays by the prism;

collimating the plurality of light rays by a single lens;

folding the plurality of light rays through one or more mirrors.

4. The method for imaging a fingerprint of claim 3, prior to the receiving step, further comprising emitting a plurality of light rays from a light source.

5. The method for imaging a fingerprint of claim 4 after the folding step, further comprising focusing the plurality of light rays through an imaging lens.

6. The method for imaging a fingerprint of claim 5 after the focusing step, further comprising detecting the plurality of light rays by a sensor.

7. An optical fingerprint sensor, comprising:

a diffuser for receiving and collimating light rays;

a prism for receiving the light rays from the diffuser, the prism reflecting the light rays when a finger surface is in contact with the upper surface of the prism;

a collimating lens for receiving the light rays from the prism and for focusing the light rays;

a first mirror for receiving the light rays from the prism and for reflecting the light rays;

a second mirror for receiving the light rays from the first mirror and for reflecting the light rays;

a third mirror for receiving the light rays form the second mirror and for reflecting the light rays; and

an imaging lens for receiving the light rays from the third mirror and focusing the light rays onto a sensor.