Infrared sensor control architecture
View Patent ↗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.
1. An infrared imaging system comprising:
a focal plane array with a plurality of pixels;
a processor operable at least in part to calculate a bucket fill level for the focal plane array;
memory including a set of non-uniform correction tables, each table with:
correction factor values including a gain and an offset; and index values unique to the table including a temperature, an integration time and a bucket fill level;
means for determining the ambient temperature of a scene; and
a calibration paddle;
where:
a non-uniform correction table is selected from memory and the correction factor values applied to the plurality of pixels minimizes temporal and fixed noise levels; and
correction factor values are determined at least in part by:
selecting three parameters of an index including at least two parameters selected from the parameter group of integration time, bucket fill level, and paddle temperature;
selecting a first set of values for parameters of the index;
configuring the infrared imaging system with the first set of parameter values;
projecting a first calibration paddle image on the focal plane array and acquiring one or more images as a first set of images;
selecting a second set of values for parameters of the index;
configuring the infrared imaging system with the second set of parameter values;
projecting a second calibration paddle image on the focal plane array and acquiring one or more images as a second set of images; and
calculating gain and offset values for a pixel from a first linear equation derived from the first set of images and a second linear equation derived from the second set of images.
2. The infrared imaging system of claim 1 where selecting a non-uniform correction table includes:
selecting an integration time;
acquiring at least one image of a scene using the selected integration time;
determining the scene temperature;
calculating a bucket fill value for the at least one acquired image;
selecting a non-uniform correction table by correlating table index values to:
the scene temperature;
the calculated bucket fill value; and
the selected integration time; and
applying the correction factor values of the selected non-uniform correction table to the plurality of pixels.
3. The infrared imaging system of claim 1 where the correction factor values are determined at least in part by:
configuring the infrared imaging system to a selected integration time and bucket fill level;
acquiring at the focal plane array a first set of one or more images of a blackbody at a first temperature;
acquiring at the focal plane array a second set of one or more images of a blackbody at a second temperature; and
calculating gain and offset values for each pixel from two or more linear equations.
4. The infrared imaging system of claim 1 where the system is configured to operate at substantially one target bucket fill value.
5. The infrared imaging system of claim 4 where the bucket fill values of the correction table index are the target bucket fill value.
6. The infrared imaging system of claim 2 where calculating a bucket fill value for the at least one acquired image includes:
selecting one or more pixels from a feature sub-region of the at least one acquired image; and
calculating a bucket fill value for the selected pixels.
7. An infrared imaging system comprising:
a focal plane array with a plurality of pixels;
a processor operable at least in part to calculate a bucket fill level for the focal plane array;
memory including a set of non-uniform correction tables, each table with:
correction factor values including a gain and an offset; and
index values unique to the table including a temperature, an integration time and a bucket fill level; and
means for determining the ambient temperature of a scene;
where:
a non-uniform correction table is selected from memory and the correction factor values applied to the plurality of pixels minimizes temporal and fixed noise levels; and
the system is configured to operate at substantially one target bucket fill value.
8. The infrared imaging system of claim 7 where the bucket fill values of the correction table index are the target bucket fill value.
9. An infrared imaging system comprising:
a focal plane array with a plurality of pixels;
a processor operable at least in part to calculate a bucket fill level for the focal plane array;
memory including a set of non-uniform correction tables, each table with:
correction factor values including a gain and an offset; and
index values unique to the table including a temperature, an integration time and a bucket fill level; and
means for determining the ambient temperature of a scene;
where:
a non-uniform correction table is selected from memory and the correction factor values applied to the plurality of pixels minimizes temporal and fixed noise levels;
selecting a non-uniform correction table includes:
selecting an integration time;
acquiring at least one image of a scene using the selected integration time; determining the scene temperature;
calculating a bucket fill value for the at least one acquired image;
selecting a non-uniform correction table by correlating table index values to:
the scene temperature;
the calculated bucket fill value; and
the selected integration time; and
applying the correction factor values of the selected non-uniform correction table to the plurality of pixels;
calculating a bucket fill value for the at least one acquired image includes:
selecting one or more pixels from a feature sub-region of the at least one acquire image; and
calculating a bucket fill value for the selected pixels.