Systems and methods for illuminating a platen in a print scanner

• US 6,954,260 B2
• Filed: 01/17/2002
• Issued: 10/11/2005
• Est. Priority Date: 01/17/2002
• Status: Expired due to Fees

• Current Assignee: Cross Match Technologies Incorporated (Assa Abloy AB)
• Original Assignee: Cross Match Technologies Incorporated (Assa Abloy AB)
• Inventors: Francis, Trent G., McClurg, George W., Carver, John F., Arnold, Joseph F., Scott, Walter G., Irving, Richard D.
• Primary Examiner(s): Stafirn, Michael P.
• Assistant Examiner(s): VALENTIN, JUAN D
• Application Number:
  US10/050,046
• Publication Number:
  US 20030133103A1
• Time in Patent Office: 1,363 Days
• Field of Search: 356/71, 359/15, 359/566, 362/31, 362/552, 362/555, 362/558, 382/124
• US Class Current: 356/71
• CPC Class Codes: G06V 10/145 Illumination specially adapted for pattern recognition, e.g. using gratings
• CPC Class Codes: G06V 40/1324 by using geometrical optics, e.g. using prisms G06V40/1312 takes precedence

Abstract

Systems and methods for illuminating a platen are provided. A hybrid illumination system uses both diffusion and collimation to efficiently provide a flat, uniform illumination at a platen. One or more diffusers are disposed between the illumination source array and a collimating lens. An illumination system is provided which uses diffused light to illuminate a platen in a print scanner. The illumination system has an illumination source array and a light wedge. The light wedge reflects light internally which makes the illumination even more diffuse. An illumination source array has a plurality of sources that emit blue/green light. In one preferred example, the blue/green light is equal to or approximately equal to 510 nm. Sources are divided into at least a center region and a perimeter region. The density of sources provided in the perimeter region is greater than in the center region to correct for natural light falloff in the illumination system. Intensity control can be preformed individually or in groups.

Claims

1. An illumination system that provides illumination for a platen in a print scanner, comprising:

an illumination source array that emits light from a plurality of discrete light sources; and

a light wedge having one end surface that receives light emitted from said illumination source array and a reflective surface that reflects light out of said light wedge toward the platen, wherein said reflective surface is a diffuse, reflective surface including a roughened surface coated by a layer of reflective paint,

whereby uniform illumination is provided to the platen.

2. The illumination system of claim 1, wherein said illumination source array comprises a plurality of sources that emit blue/green light.

3. An illumination system that provides illumination for a platen in a print scanner, comprising:

an illumination source array that emits light from a plurality of discrete light sources, wherein said plurality of sources are divided into at least a center region and a perimeter region, wherein the density of sources provided in said perimeter region is greater than in said center region; and

a light wedge having one end surface that receives light emitted from said illumination source array and a reflective surface that reflects light out of said light wedge toward the platen,

whereby, uniform illumination is provided to the platen.

4. The illumination system of claim 3, wherein the intensity of each source can be independently controlled relative to other sources such that a flat, uniform illumination is provided to the platen.

5. An illumination system that provides illumination for a platen in a print scanner, comprising:

an illumination source array that emits light from a plurality of discrete light sources; and

a light wedge having one end surface that receives light emitted from said illumination source array and a reflective surface that reflects light out of said light wedge toward the platen,

wherein said plurality of sources is divided into at least three groups in at least three respective zones, whereby, the intensity of each group of sources can be independently controlled relative to other groups such that a flat, uniform illumination is provided to the platen.

6. A method for providing efficient, uniform illumination to a platen, comprising:

arranging a plurality of discrete light sources into at least a center region and a perimeter region, wherein the density of sources provided in said perimeter region is greater than in said center region;

emitting light from said plurality of discrete sources;

passing the emitted light through a light wedge to obtain diffuse light; and

illuminating the platen with the diffuse light such that an image of a print of a finger or palm placed on the platen can be obtained.

7. The method of claim 6, wherein said emitting step includes emitting blue/green light.

8. The method of claim 6, further comprising independently controlling the intensity of each source relative to other sources such that a flat, uniform illumination is provided to the platen.

9. A method for providing efficient, uniform illumination to a platen, comprising:

arranging a plurality of discrete light sources into at least three groups in at least three respective zones;

emitting light from said plurality of discrete sources;

passing the emitted light through a light wedge to obtain diffuse light;

independently controlling the intensity of each group of sources relative to other groups of sources such that a flat, uniform illumination is provided to the platen; and

illuminating the platen with the diffuse light such that an image of a print of a finger or palm placed on the platen can be obtained.

10. For use in a print scanner, an illumination method for improving a range of grey scale shading, comprising:

emitting light in a blue/green spectrum from a plurality of discrete sources, wherein said plurality of sources are divided into at least a center region and a perimeter region, wherein the density of sources provided in said perimeter region is greater than in said center region; and

illuminating a platen, having an object with a pattern of ridges and valleys thereon, with at least part of the emitted light in the blue/green spectrum.

11. The method of claim 10, wherein the blue/green spectrum comprises a single wavelength equal to or approximately equal to 510 nm or a narrowband of wavelengths that includes a wavelength of 510 nm.

12. The method of claim 10, wherein the intensity of each source can be independently controlled relative to other sources such that a flat, uniform illumination is provided to the platen.

13. The method of claim 10, wherein said plurality of sources is divided into at least three groups in at least three respective zones, whereby the intensity of each group of sources can be independently controlled relative to other groups such that a flat, uniform illumination is provided to the platen.