Dynamic image adaptation method for adjusting the quality of digital prints

• US 7,164,440 B2
• Filed: 02/28/2003
• Issued: 01/16/2007
• Est. Priority Date: 02/28/2003
• Status: Active Grant

• Current Assignee: HID Global Corporation (Assa Abloy AB)
• Original Assignee: Cross Match Technologies Incorporated (Assa Abloy AB)
• Inventors: Cannon, Greg L
• Primary Examiner(s): Srivastava; Vivek
• Assistant Examiner(s): Hannett; James M.
• Application Number:
  US10/375,088
• Publication Number:
  US 20040170303A1
• Time in Patent Office: 1,418 Days
• Field of Search: 348/222.1, 348/229.1, 348370-371, 348/350, 382/115, 382124-127, 382168-172, 382/256, 382/291, 382/312
• US Class Current: 348/229.1
• CPC Class Codes: G06V 10/993 Evaluation of the quality of the acquired pattern
• CPC Class Codes: G06V 40/13 Sensors therefor
• CPC Class Codes: G06V 40/1347 Preprocessing; Feature extraction
• CPC Class Codes: H04N 1/00002 Diagnosis, testing or measuring; Detecting, analysing or monitoring not otherwise provided for error detection, error correction or monitoring in digital computers or digital computer components G06F11/00
• CPC Class Codes: H04N 1/00037 Detecting, i.e. determining the occurrence of a predetermined state H04N1/00031 takes precedence
• CPC Class Codes: H04N 1/0005 in service, i.e. during normal operation
• CPC Class Codes: H04N 1/00063 using at least a part of the apparatus itself, e.g. self-testing
• CPC Class Codes: H04N 1/00084 Recovery or repair, e.g. self-repair
• CPC Class Codes: H04N 1/40056 Circuits for driving or energising particular reading heads or original illumination means H04N1/401, H04N1/407 take precedence

Abstract

A dynamic image adaptation system and method for adjusting the quality of digital prints. The system includes an illumination source that illuminates an imaging surface of a live scanner optical system, the live scanner optical system scanning a biometric object placed on the imaging surface, a camera for capturing the print image of the biometric object placed on the imaging surface, a memory that stores data generated in the system, and a controller that adaptively controls at least one of the illumination source or the camera to obtain the print image with the predetermined quality. The controller adaptively controls the camera and the illumination source by adjusting one or more of contrast, gain, and integration time for the camera, and illumination for the illumination source.

Claims

1. A method for adaptive control of a system used to produce a biometric print image, comprising:

detecting an image;

identifying a biometric print image region in the image;

generating a measured histogram of the biometric print image region;

generating a desired histogram based on the measured histogram;

comparing values for starting and ending points of the measured and desired histograms to determine a difference between the starting and ending point values of the measured and desired histograms;

using the determined difference of the starting point values to adaptively control gain adjustment, illumination, and integration time; and

using the determined difference of the ending point values to adaptively control contrast, such that a predetermined quality of the biometric print image is produced.

2. The method of claim 1, further comprising the step of adaptively controlling at least one of a camera, based on the adaptive control of the contrast, the gain adjustment, or the integration time, and an illumination source, based on the adaptive control of the illumination, which form a portion of the system.

3. The method of claim 1, wherein said identifying a biometric print image region step comprises evaluating groups of pixels in the image to determine a standard deviation between the pixels in each of the groups to identify a grouping with a largest standard deviation, wherein the grouping with the largest standard deviation is masked as the biometric print image region.

4. The method of claim 1, wherein said identifying a biometric print image region step comprises the step of determining a gray area within the image in a shape of one of a square.

5. The method of claim 1, wherein said identifying a biometric print image region step comprises the step of determining a gray area within the image in a shape of one of a square or a rectangle.

6. The method of claim 1, further comprising:

determining an energy value of the measured histogram;

determining an energy value of the desired histogram;

determining an adaptive control energy based on the energy of the measured histogram and the energy of the desired histogram;

using the adaptive control energy to generate and to determine a threshold for a respective control parameter value for each of the contrast, gain adjustment,

illumination, and integration time; and

adjusting one or more of the respective control parameter values until a respective one of the thresholds is reached or the adaptive control energy is reached to adaptively control the system, such that the predetermined quality of the biometric print image is produced.

7. The method of claim 6, wherein the threshold is one of a maximum or minimum threshold based on whether the energy value of the measured histogram is above or below the energy value of the desired histogram.

8. The method of claim 6, further comprising:

determining whether one or more of the respective control parameter values cannot be adjusted, based on the generated desired histogram, such that only other ones of the respective control parameter values are adjusted.

9. The method of claim 6, wherein each of the respective control parameter values is adjusted, such that once a respective one of the upper thresholds is reached a next one of the respective control parameter values is adjusted until all the respective control parameter values have been adjusted or the adaptive control energy is reached.

10. The method of claim 6, wherein said determining the adaptive control energy step comprises determining a difference between the energy value of the measured histogram and the energy value of the desired histogram.

11. The method of claim 6, wherein said determining the energy value of the desired histogram comprises the step of using an integral function.

12. The method of claim 6, wherein said determining the energy value of the measured histogram comprises the step of using an integral function.

13. A system using adaptive control to produce a print image of a predetermined quality, the system comprising:

an illumination source that illuminates an imaging surface of a live scanner optical system, the live scanner optical system scanning a biometric object placed on the imaging surface;

a camera that captures the print image of the biometric object placed on the imaging surface;

a memory that stores data relating to the captured print image; and

a controller that is configured to;

(a) generate a measured histogram and a desired histogram based on the data relating to the captured print image, (b) compare values for starting and ending points of the measured and desired histograms to determine a difference between the starting and ending point values of the measured and desired histograms, (c) use the determined difference of the starting point values to adaptively control gain adjustment and integration time of a camera and to adaptively control illumination of the illumination source, and (d) use the determined difference of the ending point values to adaptively control contrast of the camera to obtain the print image with the predetermined quality.

14. The system of claim 13, wherein:

the illumination source comprises one or more light emitting diodes (LEDs); and

the controller adaptively controls an intensity of each of the LEDs.

15. The system of claim 13, wherein the controller is configured to:

(a) determine an adaptive control energy;

(b) generate and determine a threshold for a respective control parameter value for each of the contrast, gain adjustment, illumination, and integration time; and

(c) adjust one or more of the respective control parameter values until a respective one of the thresholds is reached or the adaptive control energy is reached to adaptively control at least one of the illumination source or the camera to obtain the print image with the predetermined quality.

16. The system of claim 15, wherein:

the adaptive control energy is based on a difference between an energy of a measured histogram and an energy of a generated desired histogram; and

the threshold is one of a maximum or minimum threshold based on whether the energy value of the measured histogram is above or below the energy value of the desired histogram.

17. The system of claim 15, wherein:

the adaptive control energy is based on a difference between an energy of a measured histogram and an energy of a generated desired histogram; and

the controller determines whether one or more of the respective control parameter values cannot be adjusted based on the generated desired histogram, such that only other ones of the respective control parameter values are adjusted.

18. The system of claim 15, wherein each of the respective control parameter values is adjusted, such that once a respective one of the upper thresholds is reached a next one of the respective control parameter values is adjusted until all the respective control parameter values have been adjusted or the adaptive control energy is reached.