Sequenced Illumination

• US 20100128964A1
• Filed: 11/25/2008
• Published: 05/27/2010
• Est. Priority Date: 11/25/2008
• Status: Active Grant

• Current Assignee: Cash Processing Solutions, Inc. (De La Rue PLC)
• Original Assignee: Cash Processing Solutions, Inc. (De La Rue PLC)
• Inventors: Blair, Ronald Bruce
• Granted Patent: US 8,780,206 B2
• Time in Patent Office: Days
• US Class Current: 382/135
• CPC Class Codes: G06V 10/141 Control of illumination
• CPC Class Codes: G06V 10/143 Sensing or illuminating at different wavelengths
• CPC Class Codes: G07D 7/121 Apparatus characterised by sensor details
• CPC Class Codes: G07D 7/205 Matching spectral properties

Abstract

The present invention provides a method and system for imaging documents such as bank notes. The method comprises passing a document past an image sensor such as a line scan camera while sequentially illuminating the document using multi-mode illumination. Two or more light sources are used, each one producing a different mode of illumination. A lookup table divides documents into discrete successive sections (i.e. scan lines) and specifies a mode of illumination (e.g., color, azimuth, reflective, transmissive) for each section of a document during imaging. As the document passes the image sensor, the light sources are activated according to the sequence specified in the lookup table, producing an interleaved, multi-mode image of the document.

Claims

1. A system for imaging documents, comprising:

(a) an image sensor;

(b) at least two different light sources, wherein each light source produces a different mode of illumination;

(c) a lookup table that divides documents into discrete successive sections and specifies a mode of illumination for each section of a document during imaging; and

(d) means for synchronizing said light sources with said image sensor to sequentially illuminate a document passing in front of the image sensor according to said lookup table, producing an interleaved, multi-mode image of said document.

2. The system according to claim 1, wherein a mode of illumination is determined by at least one of the following parameters:

color;

angle of incidence to the document;

reflective versus transmissive illumination.

3. The system according to claim 2, wherein the color of illumination is at least one of the following alone or in combination:

red;

green;

blue;

white;

infrared;

ultraviolet.

4. The system according to claim 1, wherein the system comprises up to 16 different light sources, wherein each light source produces a different mode of illumination.

5. The system according to claim 1, wherein a different lookup table is used for each document type imaged by the system.

6. The system according to claim 1, wherein the image sensor is a line scan camera and wherein the discrete sections of the document defined in the lookup table correspond to scan lines.

7. A method for imaging documents, comprising the steps of:

(a) accessing a lookup table that divides documents into discrete successive sections and specifies a mode of illumination for each section of a document during imaging;

(b) passing a document past an image sensor; and

(c) sequentially illuminating said document as it passes said image sensor using multi-mode illumination according to said lookup table to produce an interleaved, multi-mode image of said document.

8. The method according to claim 7, wherein a mode of illumination is determined by at least one of the following parameters:

color;

angle of incidence to the document;

reflective versus transmissive illumination.

9. The method according to claim 8, wherein the color of illumination is at least one of the following alone or in combination:

red;

green;

blue;

white;

infrared;

ultraviolet.

10. The method according to claim 7, further comprising using up to 16 different light sources, wherein each light source produces a different mode of illumination

11. The method according to claim 7, further comprising accessing a different lookup table for each document type imaged.

12. The method according to claim 7, wherein the image sensor is a line scan camera and wherein the discrete sections of the document defined in the lookup table correspond to scan lines.