Dither image scanner with compensation for individual detector response and gain correction

A method for dither scanning a scene using an array of detectors in order to compensate for gain and offset errors in the detector array, comprising the steps of:

• sensing images in a scene using the detector array and generating output signals from the detectors corresponding to portions of the scene observed;
• dithering the detector array according to a dither pattern, the dither pattern allowing for detector overlap and common scan paths among individual detectors in the detector array;
• correcting gain and offset errors resulting from variations in gain and offset from detector to detector in the detector array based on signals resulting from the detector overlap and the common scan paths provided by the dither pattern;
• correcting global gain errors common to all the individual detectors in the detector array;
• and
• correcting global offset errors common to all the individual detectors in the detector array.

A dither scan detector compensation apparatus for compensating for variations in gain and offset from detector to detector in a detector array, comprising:

• a detector array having a plurality of individual detectors that sense images in a scene and generate output signals corresponding to portions of the scene observed by the detector array;
• a dithering apparatus that dithers the detector array by moving the detector line of sight between consecutive frames according to a predetermined dither pattern;
• an A/D converter that digitizes the output signals from the individual detectors;
• a gain corrector that applies a gain correction factor to the digitized output signals from the individual detectors;
• an offset corrector that applies an offset correction factor to the digitized output signals from the individual detectors;
• a memory that stores the digitized output signals after gain and offset correction by the gain corrector and offset corrector for a plurality of frames of the dither pattern;
• a gain correction processor that receives detector data from the memory and calculates the gain correction factor based upon that data;
• an offset correction processor that receives detector data from the memory and calculates the offset correction factor based upon that data;
• a global gain corrector that corrects global gain errors common to all the individual detectors in the detector array;
• and
• a global offset corrector that corrects global offset errors common to all the individual detectors in the detector array.