METHOD AND APPARATUS FOR COMPENSATING FOR FIXED PATTERN NOISE IN AN IMAGING SYSTEM

• US 20140063289A1
• Filed: 11/18/2013
• Published: 03/06/2014
• Est. Priority Date: 03/28/1997
• Status: Active Grant

• Current Assignee: Hand Held Products Incorporated (Honeywell International Inc.)
• Original Assignee: Hand Held Products Incorporated (Honeywell International Inc.)
• Inventors: Hussey, Robert M., Havens, William H.
• Granted Patent: US 9,148,551 B2
• Time in Patent Office: Days
• US Class Current: 348/231.3
• CPC Class Codes: H04N 25/60 Noise processing, e.g. detecting, correcting, reducing or removing noise
• CPC Class Codes: H04N 25/63 applied to dark current
• CPC Class Codes: H04N 25/671 for non-uniformity detection or correction
• CPC Class Codes: H04N 25/674 based on the scene itself, e.g. defocusing
• CPC Class Codes: H04N 25/677 for reducing the column or line fixed pattern noise
• CPC Class Codes: H04N 5/76 Television signal recording

Abstract

The invention relates to a method and apparatus for configuring an imaging system to compensate for fixed pattern noise, variations in pixel values captured from an image sensor that vary according to a fixed pattern. In a method for configuring an imaging system for compensating an additive term component of fixed pattern noise, a pixel array is exposed to a scene of known radiance and an average white value is determined for each pixel of an array. Each average white value is compared to a predetermined reference value to determine a correction value for each pixel. In a method for configuring an imaging system for compensating both an additive and multiplicative component of fixed pattern noise, a pixel array is exposed to a first scene having a first known radiance, and frames of the scene are captured, and then the array is exposed to a second scene having a second known radiance and frames of the second scene are captured.

Claims

1. A method for configuring an imaging system, comprising:

exposing a two dimensional pixel array within the imaging system to a scene having a known radiance;

capturing a predetermined number of image signal frames of the known radiance scene;

discarding a predetermined number of pixel values in at least one column of the two dimensional pixel array when each frame is captured based on gray scale values of the pixel values;

thereafter, finding a column white value for each column of the two dimensional pixel array when each frame is captured;

averaging the column white values to determine an average column white value for each column of the two dimensional pixel array;

comparing each average column white value to a predetermined reference value for each column, and therefrom determining a correction value for each column of the two dimensional pixel array; and

storing each correction value in a storage location for retrieval by the imaging system.

2. The method of claim 1, wherein:

the step of discarding a predetermined number of pixel values in at least one column of the two dimensional pixel array comprises discarding a predetermined number of highest gray scale valued pixel values in a column; and

the step of finding a column white value for each column comprises identifying the highest gray scale value present out of the remaining pixel values of the column.

3. The method of claim 1, wherein:

the step of discarding a predetermined number of pixel values in at least one column of the two dimensional pixel array comprises discarding a predetermined number of highest gray scale valued pixel values in a column; and

the step of finding a column white value for each column comprises averaging the gray scale values of the remaining pixel values.

4. The method of claim 1, wherein the predetermined reference value of each column is a constant value in the range of column white values for the two dimensional pixel array.

5. The method of claim 1, comprising determining the predetermined reference value for a given column based on an average column white value associated with at least one column positionally related to the given column.

6. The method of claim 1, comprising determining the predetermined reference value for a given column based on an average column white value associated with the given column and an average column white value associated with at least one column positionally related to the given column.

7. A method for operating an imaging system, comprising:

determining a correction value for each of a plurality of pixels of a two dimensional pixel array within the imaging system to obtain a plurality of correction values;

capturing a frame of image data;

correcting a plurality of pixel values in the captured frame of image data using the plurality of correction values to obtain a corrected frame of image data; and

attempting to decode indicia in the corrected frame of image data.

8. The method of claim 7, comprising storing a correction value for substantially all of the pixels in the two dimensional pixel array.

9. The method of claim 7, comprising storing a correction value for substantially all of the columns in the two dimensional pixel array.

10. The method of claim 7, comprising:

storing the captured frame of image data in a memory location; and

reading the captured frame of image data from the memory location while performing the step of correcting a plurality of pixel values in the captured frame of image data.

11. The method of claim 7, wherein the steps of capturing a frame of image data and correcting a plurality of pixel values in the captured frame of image data are performed substantially contemporaneously.

12. The method of claim 7, wherein the steps of capturing a frame of image data and correcting a plurality of pixel values in the captured frame of image data are performed substantially contemporaneously and the corrected frame of image data is stored in a memory location.

13. The method of claim 7, wherein:

the step of determining a correction value comprises exposing the plurality of pixels to at least two scenes having different radiances; and

the plurality of correction values have a multiplication component and an additive component.

14. The method of claim 7, wherein the two dimensional pixel array is a monochrome pixel array.

15. A method for operating an imaging system, comprising:

exposing a two dimensional pixel array within the imaging system to a scene having a known radiance;

capturing a predetermined number of image signal frames of the known radiance scene;

discarding a predetermined number of pixel values in at least one column of the two dimensional pixel array when each frame is captured based on gray scale values of the pixel values;

thereafter, finding a column white value for each column of the two dimensional pixel array when each frame is captured;

averaging the column white values to determine an average column white value for each column of the two dimensional pixel array;

comparing each average column white value to a predetermined reference value for each column, and therefrom determining a correction value for each column of the two dimensional pixel array;

capturing a frame of image data;

correcting a plurality of pixel values in the captured frame of image data using the determined correction values to obtain a corrected frame of image data; and

attempting to decode indicia in the corrected frame of image data.

16. The method of claim 15, comprising storing a correction value for substantially all of the pixels in the two dimensional pixel array.

17. The method of claim 15, comprising storing a correction value for substantially all of the columns in the two dimensional pixel array.

18. The method of claim 15, comprising:

storing the captured frame of image data in a memory location; and

reading the captured frame of image data from the memory location while performing the step of correcting a plurality of pixel values in the captured frame of image data.

19. The method of claim 15, wherein the steps of capturing a frame of image data and correcting a plurality of pixel values in the captured frame of image data are performed substantially contemporaneously.

20. The method of claim 15, wherein the steps of capturing a frame of image data and correcting a plurality of pixel values in the captured frame of image data are performed substantially contemporaneously and the corrected frame of image data is stored in a memory location.