Method and apparatus for compensating pixel values in an imaging system

• US 8,587,697 B2
• Filed: 05/17/2010
• Issued: 11/19/2013
• Est. Priority Date: 03/28/1997
• Status: Expired due to Fees

• 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.
• Primary Examiner(s): HO, TUAN V
• Application Number:
  US12/781,595
• Publication Number:
  US 20100289919A1
• Time in Patent Office: 1,282 Days
• Field of Search: 348/241, 348/362, 348/222.1, 348/370, 348/371, 382/261, 358/406
• US Class Current: 348/241
• 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 25/677 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. After first and second average white values are determined for each pixel additive and multiplicative term correction values for each pixel are then determined by solving for a system of equations relating the first and second average white values and first and second scene radiances. Correction values can be utilized to correct pixel values of a frame of image data, and a decoding algorithm for attempting to decode a frame of image data including corrected pixel values can be activated.

Claims

1. A method for operating an imaging system, said imaging system having an image sensor including a two dimensional pixel array, said method comprising the steps of:

determining a plurality of first correction values, wherein said determining a plurality of first correction values includes determining a correction value for use in correcting pixel values corresponding to each of a plurality of pixels of said two dimensional pixel array;

determining a plurality of second correction values, wherein said determining a plurality of second correction values includes determining a correction value for use in correcting pixel values corresponding to each of said plurality of pixels of said two dimensional pixel array;

storing said first correction values and said second correction values in a memory location;

in a run mode of operation with a first operating application active, capturing a frame of image data into a memory location and correcting a plurality of pixel values of said frame using said first correction values; and

in a run mode of operation with a second operating application active, capturing a frame of image data into a memory location and correcting a plurality of values of the frame using said second correction values.

2. The method of claim 1, wherein said storing step with the first operating application active includes the step of storing a pixel correction value for substantially each pixel of said pixel array.

3. The method of claim 1, wherein said storing step with the first operating application active includes the step of storing column correction value for substantially each column of said pixel array.

4. The method of claim 1, wherein said imaging system with the first operating application active executes said correcting step subsequent to said capturing step, by storing, in said capturing step, an uncorrected frame of image data corresponding to a scene in said second memory location, and by executing said correcting step by correcting said at least one pixel value using said correction value while reading said uncorrected frame of image data from said second memory location.

5. The method of claim 1, wherein said imaging system with the first operating application active executes said correcting step substantially contemporaneously with said capturing step, by correcting said at least one pixel value using said correction value while storing said frame of image data into second memory location.

6. The method of claim 1, wherein said determining step with the first operating application active comprises an exposing step including the step of exposing said pixel array to at least two scenes having different radiances and wherein said storing step includes the step of storing a correction valued having both a multiplication component and an additive component.

7. The method of claim 1, wherein said pixel array is a monochrome pixel array.

8. The method of claim 1, wherein the first correction values are determined using a constant reference value, and wherein the second correction values are determined without using a constant reference value.

9. The method of claim 1, wherein the first operating application is a bar code decoding application and the second operating application is a video display application.

10. The method of claim 1, wherein the first correction values are for use in correcting fixed portion noise.

11. The method of claim 1, wherein the first and second correction values are for use in correcting fixed pattern noise.

12. A method for operating an imaging system, said imaging system having an image sensor including a two dimensional pixel array, said method comprising the steps of:

providing an illumination apparatus for artificial illumination of a target scene, wherein the illumination apparatus provides non-uniform illumination to a target scene;

in a run mode of operation, capturing a frame of image data into a memory location and correcting a plurality of pixel values of said frame using correction values to correct for said non-uniform illumination;

executing a decoding algorithm for attempting to decode for decodable indicia, wherein said executing step includes the step of utilizing said frame of image data having said plurality of pixel values that have been corrected utilizing said correction values.

13. The method of claim 12, wherein the method includes providing the imaging system to operate in accordance with a bar code decoding operating application.

14. The method of claim 12, wherein the method includes providing the imaging system to operate in accordance with a video display operating application.

15. The method of claim 12, wherein the method includes providing the imaging system to operate in accordance with a bar code decoding operating application, and wherein the method includes providing the imaging system to operate in accordance with a video display operating application.

16. The method of claim 12, wherein the illumination apparatus provides non-uniform illumination according to a fixed pattern.

17. The method of claim 12, wherein the illumination apparatus comprises a bank of illuminators.