Thermal image frame capture using de-aligned sensor array

• US 9,843,742 B2
• Filed: 05/14/2013
• Issued: 12/12/2017
• 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: Garrow, Stanley H., Hgasten, Nicholas, Hoelter, Theodore R., Strandemar, Katrin, Boulanger, Pierre, Sharp, Barbara, Kurth, Eric A., Ingerhed, Malin
• Primary Examiner(s): Kelley, Christopher S
• Assistant Examiner(s): WALSH, KATHLEEN M.
• Application Number:
  US13/893,809
• Publication Number:
  US 20130250125A1
• Time in Patent Office: 1,673 Days
• Field of Search: 348164, 3482084, 348260-283, 382295-297
• 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 5/33 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 capture one or more thermal image frames using an infrared sensor array that is fixably positioned to substantially de-align rows and columns of infrared sensors. In one example, an infrared imaging system includes an infrared sensor array comprising a plurality of infrared sensors arranged in rows and columns and adapted to capture a thermal image frame of a scene exhibiting at least one substantially horizontal or substantially vertical feature. The infrared imaging system also includes a housing. The infrared sensor array is fixably positioned within the housing to substantially de-align the rows and columns from the feature while the thermal image frame is captured.

Claims

1. An infrared imaging system comprising:

an infrared sensor array comprising a plurality of infrared sensors arranged in rows and columns and adapted to capture a thermal image frame of a scene exhibiting at least one horizontal or vertical feature;

a housing;

wherein the infrared sensor array is permanently positioned within the housing during manufacture to intentionally de-align the rows and columns from the at least one horizontal or vertical feature while the thermal image frame is captured to distribute the at least one feature across a plurality of the de-aligned rows and columns;

a processing device adapted to perform a row and column noise reduction process on the captured thermal image frame to determine and apply row and column fixed pattern noise offset terms to provide a processed thermal image frame, wherein the distribution of the feature across the de-aligned rows and columns causes the processed thermal image frame to exhibit reduced row and column noise artifacts resulting from the row and column noise reduction process; and

wherein the permanent position of the infrared sensor array relative to and within the housing is configured to passively de-align the rows and columns while the infrared imaging system is capturing the thermal image frame, and

wherein the infrared imaging system is adapted to be operated to capture the thermal image frame without rotating the infrared sensor array from the permanent position.

2. The infrared imaging system of claim 1, wherein:

the housing comprises a surface parallel to the at least one feature; and

the infrared sensor array is permanently positioned within the housing to intentionally de-align the rows and columns from the surface while the thermal image frame is captured.

3. The infrared imaging system of claim 2, wherein the surface is a planar external surface of the housing.

4. The infrared imaging system of claim 1, wherein the infrared sensor array is rotationally offset relative to the housing.

5. The infrared imaging system of claim 1, wherein the infrared sensor array is rotationally offset about an optical axis of the infrared imaging system.

6. The infrared imaging system of claim 1, wherein:

the captured thermal image frame comprises rows and columns of pixels intentionally de-aligned from the at least one feature; and

the processing device, for the row and column noise reduction process, is adapted to;

calculate, for each pixel, a difference between a center pixel and a plurality of neighboring pixels to determine column neighbor differences,

generate, for each column of pixels, a histogram of the column neighbor differences,

use the column neighbor differences to determine column noise offset terms for corresponding columns of pixels, and

apply column noise filter correction to the captured image based on the column noise offset terms, wherein the column noise offset term is applied to at least a majority of the pixels in each corresponding column.

7. The infrared imaging system of claim 1, wherein the thermal image frame is an unblurred thermal image frame, wherein the processing device, for the row and column noise reduction process, is adapted to:

receive an intentionally blurred thermal image frame;

process the blurred thermal image frame to determine a plurality of non-uniformity correction (NUC) terms; and

apply the NUC terms to the unblurred thermal image frame.

8. A method of operating the infrared imaging system of claim 1, the method comprising:

capturing the thermal image frame while the rows and columns are intentionally de-aligned from the at least one feature.

9. An infrared imaging system comprising:

an infrared sensor array comprising a plurality of infrared sensors arranged in rows and columns and adapted to capture a thermal image frame of a scene exhibiting at least one horizontal or vertical feature;

a housing comprising a surface parallel to the at least one feature;

wherein the infrared sensor array is permanently positioned within the housing during manufacture to intentionally de-align the rows and columns from the surface while the thermal image frame is captured to distribute the at least one feature across a plurality of the de-aligned rows and columns;

a processing device adapted to perform a row and column noise reduction process on the captured thimble image frame to determine and apply row and column fixed pattern noise offset terms to provide a processed thermal image frame, wherein the distribution of the feature across the de-aligned rows and columns causes the processed thermal image frame to exhibit reduced row and column noise artifacts resulting from the row and column noise reduction process; and

wherein the permanent position of the infrared sensor array relative to and within the housing is configured to passively de-align the rows and columns while the infrared imaging system is capturing the thermal image frame, and

wherein the infrared imaging system is adapted to be operated to capture the thermal image frame without rotating the infrared sensor array from the permanent position.

10. The infrared imaging system of claim 9, wherein the surface is a planar external surface of the housing.

11. The infrared imaging system of claim 9, wherein the infrared sensor array is permanently positioned within the housing to intentionally de-align the rows and columns from the at least one feature while the thermal image frame is captured.

12. The infrared imaging system of claim 9, wherein the infrared sensor array is rotationally offset relative to the housing.

13. The infrared imaging system of claim 9, wherein the infrared sensor array is rotationally offset about an optical axis of the infrared imaging system.

14. The infrared imaging system of claim 9, wherein:

the captured thermal image frame comprises rows and columns of pixels intentionally de-aligned from the at least one feature; and

the processing device, for the row and column noise reduction process, is adapted to;

calculate, for each pixel, a difference between a center pixel and a plurality of neighboring pixels to determine column neighbor differences,

generate, for each column of pixels, a histogram of the column neighbor differences,

use the column neighbor differences to determine column noise offset terms for corresponding columns of pixels, and

apply column noise filter correction to the captured image based on the column noise offset terms, wherein the column noise offset term is applied to at least a majority of the pixels in each corresponding column.

15. The infrared imaging system of claim 9, wherein the thermal image frame is an unblurred thermal image frame, the processing device, for the row and column noise reduction process, is adapted to:

receive an intentionally blurred thermal image frame;

process the blurred thermal image frame to determine a plurality of non-uniformity correction (NUC) terms; and

apply the NUC terms to the unblurred thermal image frame.

16. A method of operating the infrared imaging system of claim 9, the method comprising:

capturing the thermal image frame while the rows and columns are intentionally de-aligned from the at least one feature.

17. A method comprising:

capturing a thermal image frame of a scene exhibiting at least one substantially horizontal or vertical feature;

wherein the capturing is performed by an infrared sensor array comprising a plurality of infrared sensors arranged in rows and columns;

wherein the infrared sensor array is permanently positioned within a housing of an infrared imaging system, the infrared sensory array being permanently positioned within the housing during manufacture to intentionally de-align the rows and columns from the at least one substantially horizontal or vertical feature while the thermal image frame is captured;

performing row and column noise reduction process on the captured thermal image frame to determine and apply row and column fixed pattern noise offset terms to provide a processed thermal image frame;

wherein a distribution of the feature across the de-aligned rows and columns causes the processed thermal image frame to exhibit reduced row and column noise artifacts resulting from the row and column noise reduction process; and

wherein the permanent position of the infrared sensor array relative to and within the housing is configured to passively de-align the rows and columns while the infrared imaging system is capturing the thermal image frame, and

wherein the infrared imaging system is adapted to be operated to capture the thermal image frame without rotating the infrared sensor array from the permanent position.

18. The method of claim 17, further comprising:

providing the infrared sensor array;

providing the housing; and

permanently positioning the infrared sensor array within the housing to intentionally de-align the rows and columns.

19. The method of claim 17, wherein:

the housing comprises a surface parallel to the at least one feature; and

the infrared sensor array is fixably and securely positioned within the housing to intentionally de-align the rows and columns from the surface while the thermal image frame is captured.

20. The method of claim 19, wherein the surface is a planar external surface of the housing.

21. The method of claim 17, wherein the infrared sensor array is rotationally offset relative to the housing.

22. The method of claim 17, wherein the infrared sensor array is rotationally offset about an optical axis of the infrared imaging system.

23. The method of claim 17, wherein:

the captured thermal image frame comprises rows and columns of pixels intentionally de-aligned from the at least one feature; and

the method further comprises;

calculating, for each pixel, a difference between a center pixel and a plurality of neighboring pixels to determine column neighbor differences,

generating, for each column of pixels, a histogram of the column neighbor differences,

using the column neighbor differences to determine column noise offset terms for corresponding columns of pixels, and

applying column noise filter correction to the captured image based on the column noise offset terms, wherein the column noise offset term is applied to at least a majority of the pixels in each corresponding column.

24. The method of claim 17, wherein:

the thermal image frame is an unblurred thermal image frame; and

the method further comprises;

receiving an intentionally blurred thermal image frame,

processing the blurred thermal image frame to determine a plurality of non-uniformity correction (NUC) terms, and

applying the NUC terms to the unblurred thermal image frame.

25. An infrared imaging system adapted to be operated in accordance with the method of claim 17.