Method of shutterless non-uniformity correction for infrared imagers

• US 10,057,512 B2
• Filed: 11/16/2016
• Issued: 08/21/2018
• Est. Priority Date: 03/15/2013
• Status: Active Grant

• Current Assignee: DRS Network & Imaging Systems, LLC (Leonardo S.p.A.)
• Original Assignee: DRS Network & Imaging Systems, LLC (Leonardo S.p.A.)
• Inventors: Bailey, John R., Allred, Rustin W.
• Primary Examiner(s): Alavi, Amir
• Application Number:
  US15/353,655
• Publication Number:
  US 20170163908A1
• Time in Patent Office: 643 Days
• CPC Class Codes: G06T 2207/10048 Infrared image
• CPC Class Codes: G06T 5/00 Image enhancement or restoration
• CPC Class Codes: G06T 5/77 Retouching; Inpainting; Scratch removal
• CPC Class Codes: G06T 7/13 Edge detection
• CPC Class Codes: G06T 7/20 Analysis of motion motion estimation for coding, decoding, compressing or decompressing digital video signals H04N19/43, H04N19/51
• CPC Class Codes: H04N 5/33 Transforming infrared radiation cameras or camera modules for generating image signals from infrared radiation H04N23/20; circuitry of SSIS for transforming infrared radiation into image signals H04N25/20

Abstract

A method of correcting an infrared image including a plurality of pixels arranged in an input image array, a first pixel in the plurality of pixels having a first pixel value and one or more neighbor pixel with one or more neighbor pixel values. The first pixel and the one or more neighbor pixels are associated with an object in the image. The method includes providing a correction array having a plurality of correction pixel values, generating a corrected image array by adding the first pixel value to a correction pixel value in the correction array, and detecting edges in the corrected image array. The method also includes masking the detected edges in the corrected image array, updating the correction array, for each correction pixel value in the correction array and providing an output image array based on the correction array and the input image array.

Claims

1. A method of correcting an infrared image, the method comprising:

providing a processor;

receiving the infrared image from a camera, the infrared image comprising a plurality of pixels arranged in an input image array, a first pixel in the plurality of pixels having a first pixel value and one or more neighbor pixels with one or more neighbor pixel values, wherein the first pixel and the one or more neighbor pixels are associated with an object in the image, the one of more neighbor pixels being adjacent to the first pixel in the input image array;

processing the infrared image to generate a processed image;

providing a correction array having a plurality of correction pixel values;

providing a corrected image based on the correction array and the processed image;

determining, by the processor, that the camera is moving;

detecting edges in the corrected image; and

updating the correction array for each correction pixel value in the correction array; and

providing an output image based on the updated correction array and the processed image; and

determining, by the processor, that the camera is not moving;

providing the corrected image as the output image,

wherein the processed image is a product of the received infrared image with a gain factor and a sum of the product and an offset table, and

wherein the corrected image is the processed image summed with a correction array updated in a previous frame.

2. The method of claim 1, wherein updating the correction array comprises:

determining that a first pixel value of the corrected image is not an edge;

for each of the one or more neighbor pixel values of the correction array, determining that the neighbor pixel value is not an edge;

computing a difference between a previous first pixel value of the corrected image and the one or more previous neighbor pixel values of the correction array; and

updating the correction array based on a fraction of the difference.

3. The method of claim 2, wherein the fraction of the difference is computed by dividing the difference by a predetermined value.

4. The method of claim 2, wherein updating the correction array comprises:

updating a current first correction value of the first pixel by subtracting the fraction of the difference from a previous first correction value of the first pixel; and

updating one or more current correction pixel values by adding the fraction of the difference to respective one or more previous correction pixel values for the one or more neighbor pixels.

5. The method of claim 1, wherein the processed image is generated by multiplying the received infrared image by a gain factor to obtain a product and adding an offset array to the product.

6. A method of correcting an infrared image, the method comprising:

providing a processor;

receiving the infrared image from a camera, the infrared image comprising a plurality of pixels arranged in an input image array, a first pixel in the plurality of pixels having a first pixel value and one or more neighbor pixels with one or more neighbor pixel values, wherein the first pixel and the one or more neighbor pixels are associated with an object in the image, the one of more neighbor pixels being adjacent to the first pixel in the input image array;

processing the infrared image to generate a processed image;

providing a correction array having a plurality of correction pixel values;

providing a corrected image based on the correction array and the processed image;

determining that the camera is moving;

updating, by the processor, the correction array for each correction pixel value in the correction array; and

providing an output image based on the updated correction array and the processed image; and

determining that the camera is not moving;

providing the corrected image as the output image.

7. The method of claim 6, wherein updating the correction array comprises:

determining correction pixel values for the one or more neighbor pixels; and

computing a difference between a first correction value of the first pixel value and one or more correction pixel values for the one or more neighbor pixels.

8. The method of claim 7, wherein computing the difference comprises computing a difference between the first correction value and each of the correction pixel values for the one or more neighbor pixels.

9. The method of claim 8, wherein updating the correction array comprises determining that an absolute value of the difference of the difference is within a range.

10. The method of claim 9, wherein updating the correction array comprises determining that an absolute value of the difference is within a range;

if the absolute value of the difference is within the range;

updating a current first correction value of the first pixel by subtracting a fraction of the difference from the previous first correction value of the first pixel; and

updating one or more current correction pixel values for the one or more neighbor pixels by adding the fraction of the difference to the one or more respective previous correction pixel values for the one or more neighbor pixels.

11. The method of claim 10, wherein the fraction of the difference is computed by dividing the difference by a denominator, wherein the denominator is a predetermined value.

12. A method of correcting an infrared image, the method comprising:

providing a processor;

receiving the infrared image from a camera, the infrared image comprising a plurality of pixels arranged in an input image array, a first pixel in the plurality of pixels having a first pixel value and one or more neighbor pixels with one or more neighbor pixel values, wherein the first pixel and the one or more neighbor pixels are associated with an object in the image, the one of more neighbor pixels being adjacent to the first pixel in the input image array;

processing the infrared image to generate a processed image;

providing a correction array having a plurality of correction pixel values;

providing a corrected image based on the correction array and the processed image;

determining, by the processor, that the camera is moving;

detecting edges in the corrected image; and

updating the correction array for each correction pixel value in the correction array; and

providing an output image based on the updated correction array and the processed image; and

determining, by the processor, that the camera is not moving;

for each pixel of the processed image, computing a difference between a previous first correction value of the first pixel and one or more previous correction pixel values for the one or more neighbor pixels;

determining that an absolute value of the difference is within a range;

if the absolute value of the difference is within the range;

updating a current first correction value of the first pixel by subtracting a fraction of the difference from the previous first correction value of the first pixel; and

updating one or more current correction pixel values for the one or more neighbor pixels by adding the fraction of the difference to the one or more respective previous correction pixel values for the one or more neighbor pixels; and

providing the output image based on the updated correction array and the processed image.

13. The method of claim 12, wherein updating the correction array when the camera is determined to be moving comprises:

updating a current first correction value of the first pixel by subtracting the fraction of the difference from a previous first correction value of the first pixel; and

updating one or more current correction pixel values by adding the fraction of the difference to respective one or more previous correction pixel values for the one or more neighbor pixels.

14. The method of claim 13, wherein the output image array is a sum of the processed image and the updated correction array.

15. The method of claim 14, wherein the processed image is generated by multiplying the received infrared image by a gain factor to obtain a product and adding an offset array to the product.

16. A method of correcting an infrared image, the method comprising:

providing a processor;

receiving the infrared image from a camera, the infrared image comprising a plurality of pixels arranged in an input image array, a first pixel in the plurality of pixels having a first pixel value and one or more neighbor pixels with one or more neighbor pixel values, wherein the first pixel and the one or more neighbor pixels are associated with an object in the image, the one of more neighbor pixels being adjacent to the first pixel in the input image array;

processing, by the processor, the infrared image to generate a processed image;

determining that the camera is moving;

updating the correction array, wherein updating the correction array comprises;

for each pixel of the corrected image, computing a difference between a previous first correction value of the first pixel and one or more previous correction pixel values for the one or more neighbor pixels;

determining that an absolute value of the difference is within a first range defined by a first lower threshold and a first upper threshold;

if the absolute value of the difference is within the first range;

updating a current first correction value of the first pixel by subtracting a fraction of the difference from the previous first correction value of the first pixel; and

updating one or more current correction pixel values for the one or more neighbor pixels by adding the fraction of the difference to the one or more respective previous correction pixel values for the one or more neighbor pixels; and

providing an output image based on the processed image and the updated correction array; and

determining that the camera is not moving;

updating the correction array, wherein updating the correction array comprises;

for each pixel of the corrected image, computing a difference between a previous first correction value of the first pixel and one or more previous correction pixel values for the one or more neighbor pixels;

determining that an absolute value of the difference is within a second range defined by a second lower threshold that is higher than the first lower threshold and a second upper threshold that is lower than the first upper threshold;

if the absolute value of the difference is within the second range;

updating a current first correction value of the first pixel by subtracting a fraction of the difference from the previous first correction value of the first pixel; and

updating one or more current correction pixel values for the one or more neighbor pixels by adding the fraction of the difference to the one or more respective previous correction pixel values for the one or more neighbor pixels; and

providing the output image based on the processed image and the updated correction array.

17. The method of claim 16, wherein the processes image is a product of the received infrared image with a gain factor and a sum of the product and an offset table.

18. The method of claim 16, wherein determining that the camera is moving comprises using a motion sensor in the camera.

19. The method of claim 16, wherein determining that the camera is moving comprises using image processing-based techniques.