Anomalous pixel detection

• US 9,756,264 B2
• Filed: 06/25/2015
• Issued: 09/05/2017
• Est. Priority Date: 03/02/2009
• Status: Active Grant

• Current Assignee: Teledyne FLIR LLC (Teledyne Technologies Incorporated)
• Original Assignee: FLIR Systems, Inc. (Teledyne Technologies Incorporated)
• Inventors: Hoelter, Theodore R., Hgasten, Nicholas, Ingerhed, Malin, Nussmeier, Mark, Kurth, Eric A., Strandemar, Katrin, Boulanger, Pierre, Sharp, Barbara
• Primary Examiner(s): Patel, Kanjibhai
• Application Number:
  US14/750,781
• Publication Number:
  US 20150312489A1
• Time in Patent Office: 803 Days
• Field of Search: 382264, 382274-275
• CPC Class Codes: G06T 2207/10048 Infrared image
• CPC Class Codes: G06T 5/20 using local operators
• CPC Class Codes: G06T 5/70 Denoising; Smoothing
• CPC Class Codes: H04N 23/55 Optical parts specially adapted for electronic image sensors; Mounting thereof
• CPC Class Codes: H04N 23/57 Mechanical or electrical details of cameras or camera modules specially adapted for being embedded in other devices
• CPC Class Codes: H04N 23/673 based on contrast or high frequency components of image signals, e.g. hill climbing method
• 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 25/683 by defect estimation performed on the scene signal, e.g. real time or on the fly detection
• 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

Various techniques are provided to identify anomalous pixels in images captured by imaging devices. In one example, an infrared image frame is received. The infrared image frame is captured by a plurality of infrared sensors based on infrared radiation passed through an optical element. A pixel of the infrared image frame is selected. A plurality of neighborhood pixels of the infrared image frame are selected. Values of the selected pixel and the neighborhood pixels are processed to determine whether the value of the selected pixel exhibits a disparity in relation to the neighborhood pixels that exceeds a maximum disparity associated with a configuration of the optical element and the infrared sensors. The selected pixel is selectively designated as an anomalous pixel based on the processing.

Claims

1. A method comprising:

receiving an infrared image frame captured by a plurality of infrared sensors based on infrared radiation passed through an optical element configured to exhibit an Airy disk diffraction pattern in response to a point source, wherein a width between minima of the Airy disk is greater than a width of at least two adjacent ones of the infrared sensors;

selecting a first pixel of the infrared image frame;

selecting a second pixel of the infrared image frame adjacent to the first pixel;

processing values of the selected first pixel and the selected second pixel to determine whether a ratio of the values of the selected first and second pixels exceeds a maximum ratio associated with the configuration of the optical element and the infrared sensors; and

selectively designating the selected first pixel as an anomalous pixel based on the processing.

2. The method of claim 1, further comprising selecting a plurality of neighborhood pixels of the infrared image frame, wherein the processing further comprises determining whether the value of the selected first pixel exceeds a threshold value comprising a percentage of a sum of the values of the selected first pixel and the neighborhood pixels.

3. The method of claim 1, further comprising selecting a plurality of neighborhood pixels of the infrared image frame, wherein the processing further comprises determining whether an absolute difference between the value of the selected first pixel and an average of the values of the neighborhood pixels exceeds a threshold value.

4. The method of claim 1, further comprising high pass filtering the infrared image frame prior to the processing.

5. The method of claim 1, wherein the selected first pixel is not designated as an anomalous pixel if the value of the selected first pixel is less than a background noise threshold.

6. The method of claim 1, further comprising, if the selected first pixel is designated as an anomalous pixel, identifying the selected first pixel in a bad pixel map.

7. The method of claim 1, wherein the infrared image frame is a first infrared image frame, wherein the selected first pixel is designated as an anomalous pixel during a first iteration of the method, the method further comprising:

performing a second iteration of the method using a second infrared image frame; and

designating the selected first pixel as a non-anomalous pixel based on the second iteration of the processing.

8. The method of claim 1, further comprising, if the selected first pixel is designated as an anomalous pixel, correcting the value of the selected first pixel.

9. The method of claim 8, wherein the correcting comprises determining a non-uniformity correction (NUC) term associated with the selected first pixel.

10. The method of claim 9, wherein the infrared image frame is an intentionally blurred image frame.

11. The method of claim 1, further comprising processing the infrared image frame to determine a plurality of column correction terms to reduce noise introduced by an infrared imaging device, wherein each column correction term is associated with a corresponding column of the infrared image frame and is determined based on relative relationships between pixels of the corresponding column and pixels of a neighborhood of columns.

12. The method of claim 1, wherein the infrared image frame is a thermal image frame.

13. The method of claim 1, further comprising:

passing the infrared radiation through the optical element; and

capturing the infrared image frame using the infrared sensors.

14. A system comprising:

a memory adapted to receive an infrared image frame captured by a plurality of infrared sensors based on infrared radiation passed through an optical element configured to exhibit an Airy disk diffraction pattern in response to a point source, wherein a width between minima of the Airy disk is greater than a width of at least two adjacent ones of the infrared sensors; and

a processor adapted to execute instructions to;

select a first pixel of the infrared image frame,

select a second pixel of the infrared image frame adjacent to the first pixel,

process values of the selected first pixel and the selected second pixel to determine whether a ratio of the values of the selected first and second pixels exceeds a maximum ratio associated with the configuration of the optical element and the infrared sensors, and

selectively designate the selected first pixel as an anomalous pixel based on the process.

15. The system of claim 14, further comprising a plurality of neighborhood pixels, wherein the instructions to process the values of the selected first pixel and the neighborhood pixels are adapted to cause the processor to determine whether the value of the selected first pixel exceeds a threshold value comprising a percentage of a sum of the values of the selected first pixel and the neighborhood pixels.

16. The system of claim 14, further comprising a plurality of neighborhood pixels, wherein the instructions to process the values of the selected first pixel and the neighborhood pixels are adapted to cause the processor to determine whether an absolute difference between the value of the selected first pixel and an average of the values of the neighborhood pixels exceeds a threshold value.

17. The system of claim 14, wherein the processor is adapted to execute instructions to high pass filter the infrared image frame prior to the process.

18. The system of claim 14, wherein the selected first pixel is not designated as an anomalous pixel if the value of the selected first pixel is less than a background noise threshold.

19. The system of claim 14, wherein the processor is adapted to execute instructions to, if the selected first pixel is designated as an anomalous pixel, identify the selected first pixel in a bad pixel map.

20. The system of claim 14, wherein the infrared image frame is a first infrared image frame, wherein the selected first pixel is designated as an anomalous pixel during a first execution of the instructions, wherein the processor is adapted to:

perform a second execution of the instructions using a second infrared image frame; and

execute additional instructions to designate the selected first pixel as a non-anomalous pixel based on the second execution of the process.

21. The system of claim 14, wherein the processor is adapted to execute additional instructions to, if the selected first pixel is designated as an anomalous pixel, correct the value of the selected first pixel.

22. The system of claim 21, wherein the instructions to correct the value of the selected first pixel are adapted to cause the processor to determine a non-uniformity correction (NUC) term associated with the selected first pixel.

23. The system of claim 22, wherein the infrared image frame is an intentionally blurred image frame.

24. The system of claim 14, wherein the processor is adapted to execute additional instructions to process the infrared image frame to determine a plurality of column correction terms to reduce noise introduced by an infrared imaging device, wherein each column correction term is associated with a corresponding column of the infrared image frame and is determined based on relative relationships between pixels of the corresponding column and pixels of a neighborhood of columns.

25. The system of claim 14, wherein the infrared image frame is a thermal image frame.

26. The system of claim 14, further comprising:

the optical element; and

the infrared sensors.

27. The system of claim 26, wherein the infrared sensors are microbolometers adapted to receive a bias voltage selected from a range of approximately 0.2 to approximately 0.7 volts.