INFRARED SENSOR CONTROL ARCHITECTURE

• US 20130307991A1
• Filed: 06/06/2013
• Published: 11/21/2013
• Est. Priority Date: 11/06/2009
• Status: Active Grant

• Current Assignee: Sightline Applications, LLC
• Original Assignee: Jordan Holt, Steven Olsen
• Inventors: Holt, Jordan, Olsen, Steven
• Granted Patent: US 9,332,197 B2
• Time in Patent Office: Days
• US Class Current: 348/164
• CPC Class Codes: H01L 27/14649 Infrared imagers
• CPC Class Codes: H04N 23/20 for generating image signals from infrared radiation only
• CPC Class Codes: H04N 25/673 by using reference sources
• 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 system and method for optimizing fixed and temporal noise in an infrared imaging system. The system may use correction tables with correction factors, each correction factor indexed to a plurality of system parameters.

Claims

1. A method for operating an infrared imaging system with an array of pixels comprising:

developing correction tables for the array of pixels including;

correction factors with offset and gain values for each pixel; and

an index of unique values for each correction table with;

an integration time value;

a bucket fill value; and

a temperature value;

acquiring at least one calibrating scene image with a selected integration time;

determining bucket fill level of the at least one calibrating scene image;

determining a scene temperature of the at least one calibrating scene image;

selecting a correction table by indexing the selected integration time, determined temperature and determined bucket fill level to correction table index values;

applying the correction factors of the selected correction table to the array of pixels; and

capturing a second image.

2. The method for operating an infrared imaging system of claim 1 where developing a correction table includes defining values for bucket fill levels, temperature and integration time to be incorporated in indexes.

3. The method for operating an infrared imaging system of claim 2 where developing a correction table includes configuring the imaging system to each unique set of index values and capturing an image.

4. The method for operating an infrared imaging system of claim 1 where capturing a second image includes operating the imaging system to maintain a target bucket fill level.

5. The method for operating an infrared imaging system of claim 4 where developing correction tables includes substantially limiting the bucket fill value of the index to the target bucket fill level.

6. The method for operating an infrared imaging system of claim 4 where operating the imaging system to maintain a target bucket fill level includes iteratively:

capturing one or more images;

determining the difference between the target till bucket level and the calculated bucket fill;

calculating the bucket fill for each of the one or more images; and

selecting an integration time based on the calculated bucket fill.

7. The method for operating an infrared imaging system of claim 1 where capturing a second image includes applying a histogram equalization algorithm to the captured image.

8. A method for minimizing a noise equivalent temperature difference value of a focal plane array with pixels in an infrared imaging system comprising:

defining a group of bucket fill levels;

defining a group of integration times;

defining a group of temperatures;

creating pixel data by

creating an index by selecting one value for each of bucket fill level, integration time and temperature from each defined group;

setting a substantially blackbody to the selected temperature value of the index;

setting the integration time of the imaging system to the selected integration time value of the index;

setting the bucket fill level of the imaging system to the selected bucket fill level value of the index;

with the blackbody image focused on the focal plane array, capturing one or more data images; and

saving to memory the pixel data of the data image indexed to the selected index values;

repeating the creating step for each unique set of index values;

for each pixel calculating correction factors by solving;

a first linear equation of pixel data of a first index; and

a second linear equation of pixel data of a second index;

storing the calculated correction factor in memory with the first index as a correction factor index;

acquiring an image of a scene at a selected integration time;

determining scene temperature;

calculating a bucket fill level from one or more pixels selected from the acquired image;

selecting correction factors from memory by correlating correction factor index values to calculated bucket fill level, integration time and scene temperature; and

applying the selected correction factors to pixels of the focal plane array.

9. The method for minimizing the noise equivalent temperature difference of a focal plane array of claim 8 where the group of bucket fill levels has one value.

10. The method for minimizing the noise equivalent temperature difference of a focal plane array of claim 8 where the infrared imaging system is configured to acquire images at one target bucket fill value.

11. The method for minimizing the noise equivalent temperature difference of a focal plane array of claim 10 where configuring the imaging system to operate at one bucket fill value includes iteratively acquiring a scene image, calculating the bucket fill level of the acquired scene image, resetting integration time and acquiring a scene image.

12. The method for minimizing the noise equivalent temperature difference of a focal plane array of claim 8 where a histogram equalization algorithm is applied to the acquired image.

13. The method for minimizing the noise equivalent temperature difference of a focal plane array of claim 8 where the one or more pixels selected from the acquired image are selected from a feature sub-region of the acquired image.