Flat field correction systems and methods for infrared cameras

Patent metadata

Field	Value
Publication number	US-10986288-B2
Application number	US-202016735964-A
Country	US
Kind code	B2
Filing date	Jan 7, 2020
Priority date	Jul 27, 2017
Publication date	Apr 20, 2021
Grant date	Apr 20, 2021

Abstract

Various techniques are provided to perform flat field correction (FFC) for infrared cameras. In one example, a system includes a focal plane array (FPA) of an infrared camera configured to capture thermal image data in response to infrared radiation received by the FPA via an optical path of the infrared camera. The system further includes a memory configured to store a set of supplemental FFC values. The system further includes a processor configured to determine a scale factor based at least on a temperature and/or a rate of temperature change of an internal component of the infrared camera; generate a scaled set of supplemental FFC values based on the scale factor and set of supplemental FFC values; and apply the scaled set of supplemental FFC values to the thermal image data to adjust for non-uniformities associated with at least a portion of the first optical path.

First claim

We claim:

1. A system, comprising:
a focal plane array (FPA) of an infrared camera configured to capture thermal image data in response to infrared radiation received by the FPA via a first optical path of the infrared camera;
a memory configured to store a set of supplemental flat field correction (SFFC) values; and
a processor configured to:
determine a temperature of an internal component of the infrared camera;
determine a scale factor based at least on the temperature and/or a rate of temperature change of the internal component;
apply an edge-aware low pass filter to the set of SFFC values to obtain a filtered set of SFFC values;
generate a scaled set of SFFC values based at least on the scale factor and the filtered set of SFFC values; and
apply the scaled set of SFFC values to the thermal image data to adjust for non-uniformities associated with at least a portion of the first optical path.

2. The system of claim 1 , further comprising one or more temperature sensors, wherein the processor is further configured to:
receive temperature data associated with the internal component from the one or more temperature sensors; and
determine the temperature and/or the rate of temperature change of the internal component based at least on the received temperature data, wherein the internal component comprises the FPA, the processor, the memory, a power block, a motor, a shutter, a lens barrel, a lens, a mirror, or a window.

3. The system of claim 1 , wherein:
the processor is further configured to determine a temperature of one or more other internal components of the infrared camera; and
the processor is configured to determine the scale factor further based on the temperature and/or a rate of temperature change of the one or more other internal components.

4. The system of claim 1 , wherein the scale factor is further based on a time difference between a current time and a most recent turn-on time of the infrared camera.

5. The system of claim 1 , wherein:
the processor is further configured to apply a dampening factor to the scale factor to obtain a dampened scale factor, the scaled set of SFFC values being based at least on the dampened scale factor and the filtered set of SFFC values;
the scale factor is associated with a first-time instance; and
the dampening factor is based on the determined scale factor and one or more scale factors associated with a time instance earlier than the first-time instance.

6. The system of claim 1 , wherein the internal component comprises the FPA, wherein the processor is configured to:
determine a temperature of the FPA;
determine a rate of temperature change of the FPA; and
determine the scale factor based at least on the temperature and the rate of temperature change of the FPA.

7. The system of claim 6 , wherein the scale factor is further based on a time difference between a current time and a most recent turn-on time of the infrared camera, and wherein the processor is configured to determine the scale factor independent of the rate of temperature change of the FPA when the time difference is greater than a threshold time difference.

8. The system of claim 1 , wherein:
the memory is further configured to store the filtered set of SFFC values.

9. The system of claim 1 , further comprising a shutter located between the FPA and a lens and/or optics block of the infrared camera, wherein the processor is configured to:
calibrate the FPA to an external scene to determine a first set of FFC values associated with the first optical path from the external scene to the FPA;
calibrate the FPA to the shutter to determine a second set of FFC values associated with a second optical path from the shutter to the FPA;
use the first and second set of FFC values to determine the set of SFFC values; and
store the set of SFFC values in the memory.

10. The system of claim 1 , wherein the memory is configured to store a plurality of sets of SFFC values to adjust for non-uniformities associated with different optical configurations which may be selectively inserted into the first optical path and/or different configurations of the infrared camera.

11. A method, comprising:
capturing thermal image data at a focal plane array (FPA) of an infrared camera via an optical path of the infrared camera;
determining a temperature of an internal component of the infrared camera;
determining a first scale factor based at least on the temperature and/or a rate of temperature change of the internal component;
applying an edge-aware low pass filter to a set of supplemental flat field correction (SFFC) values to obtain a filtered set of SFFC values;
generating a first scaled set of SFFC values based at least on the first scale factor and the filtered set of SFFC values; and
applying the first scaled set of SFFC values to the thermal image data to adjust for non-uniformities associated with at least a portion of the optical path.

12. The method of claim 11 , further comprising:
applying a temporal dampening factor to the first scale factor to obtain a temporally-dampened scale factor, the first scaled set of SFFC values being based at least on the temporally-dampened scale factor and the filtered set of SFFC values;
the first scale factor is associated with a first-time instance; and
the temporal dampening factor is based on the determined first scale factor and one or more scale factors associated with a time instance earlier than the first-time instance.

13. The method of claim 11 , wherein the first scale factor is further based on a temperature and/or a rate of temperature change associated with one or more other internal components of the infrared camera, wherein the internal component comprises the FPA, and wherein the first scale factor is based at least on the temperature and the rate of temperature change of the FPA.

14. The method of claim 13 , wherein the temperature, rate of temperature change, and first scale factor are associated with a first-time instance, and wherein the first scale factor is further based on a time difference between the first-time instance and a most recent turn-on time of the infrared camera.

15. The method of claim 14 , further comprising:
determining a second scale factor independent of a rate of temperature change of the FPA, wherein the second scale factor is associated with a second-time instance subsequent to the first-time instance, and wherein a time difference between the second-time instance and the most recent turn-on time is greater than a threshold time difference;
generating a second scaled set of SFFC values based at least on the second scale factor and the second set of SFFC values; and
applying the second scaled set of SFFC values to second thermal image data to adjust for non-uniformities associated with at least a portion of the optical path.

16. A non-transitory machine-readable storage medium including machine-readable instructions which, when executed, cause one or more processors of a device to perform operations comprising:
determining a temperature of an internal component of an infrared camera, wherein the internal component comprises a focal plane array (FPA);
determining a scale factor based at least on the temperature and/or a rate of temperature change of the internal component, wherein the scale factor is based at least on the rate of temperature change of the FPA when a time difference between a current time and a most recent turn-on time of the infrared camera is not greater than a threshold time difference, and wherein the scale factor is independent of the rate of temperatur

Assignees

• Flir Systems

Inventors

• Kostrzewa Joseph
• Gardner Jason

Classifications

• H04N17/002 Primary

  for television cameras · CPC title

• H04N23/23

  from thermal infrared radiation · CPC title

• H04N5/33 Primary

  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) · CPC title