Spatial light modulator seeker calibration
In certain embodiments, an imaging system includes an enclosure with an objective aperture opening into an interior space of the enclosure, an optical assembly optically coupling the objective aperture to an imaging sensor within the enclosure, a spatial light modulator (SLM) mounted to the objective aperture for selectively blocking and admitting illumination through the objective aperture into the interior space, and an illuminator mounted to illuminate the interior space of the enclosure.
1. An imaging system used in a moving platform for guiding the moving platform, the imaging system comprising:
an enclosure with an objective aperture opening into an interior space of the enclosure;
an optical assembly optically coupling the objective aperture to an imaging sensor within the enclosure;
a spatial light modulator (SLM) mounted to the objective aperture for selectively blocking and admitting illumination through the objective aperture into the interior space;
an illuminator mounted to illuminate the interior space of the enclosure;
an imaging board, wherein the imaging sensor is operatively connected to the imaging board;
a SLM controller operatively connected to the imaging board to control the SLM; and
an illuminator controller operatively connected to the imaging board to control the illuminator, wherein the imaging board includes machine readable instructions configured to cause the imaging board to perform an imaging system calibration, the imaging system calibration comprising:
blocking, with the SLM, illumination outside the enclosure from reaching the interior space;
illuminating, with the illuminator, the interior space; and
capturing, with the imaging sensor, a calibration image using illumination from the illuminator; and wherein the machine readable instructions are further configured to cause the imaging system to provide an imaging mode for guiding the moving platform, wherein in the imaging mode the blocking further includes using the SLM to actively block one or more bright spots from reaching the imaging sensor.
2. The imaging system as recited in claim 1 , further comprising, a window disposed in the objective aperture bounding the interior space together within the enclosure, wherein the SLM is assembled to the window.
3. The imaging system as recited in claim 1 , wherein the machine readable instructions are configured to further cause the imaging board to use the calibration image to calibrate the imaging sensor for capturing images with non-uniformity correction.
4. The imaging system as recited in claim 3 , wherein the machine readable instructions are configured to further cause the imaging board to compensate for an illumination gradient on the imaging sensor from non-uniform illumination from the illuminator on the imaging sensor.
5. The imaging system as recited in claim 4 , wherein the machine readable instructions are configured to further cause the imaging board to run calibration at multiple illumination levels of the illuminator and form a respective calibration image at each illumination level for non-uniformity calibration.
6. The imaging system as recited in claim 5 , wherein the machine readable instructions are configured to further cause the imaging board to form non-uniformity corrected images after calibration is complete.
7. The imaging system as recited in claim 1 , wherein the imaging sensor is sensitive to SWIR wavelengths.
8. A method used in an imaging system for guiding a moving platform comprising:
performing a calibration of the imaging system by:
blocking, with an SLM mounted to an objective aperture, illumination outside an enclosure of the objective aperture from reaching an interior space of the enclosure;
illuminating, with an illuminator, the interior space; and
capturing, with an imaging sensor optically coupled to the objective aperture, a calibration image using illumination from the illuminator; and
in an imaging mode for guiding the moving platform, using the SLM to actively block one or more bright spots from reaching the imaging sensor.
9. The method as recited in claim 8 , further comprising, using the calibration image to calibrate the imaging sensor for capturing images with non-uniformity correction.
10. The method as recited in claim 9 , further comprising compensating for an illumination gradient on the imaging sensor from non-uniform illumination from the illuminator on the imaging sensor.
11. The method as recited in claim 10 , further comprising, running calibration at multiple illumination levels of the illuminator and forming a respective calibration image at each illumination level for non-uniformity calibration.
12. The method as recited in claim 11 , further comprising forming non-uniformity corrected images after calibration is complete.
13. The method as recited in claim 12 , wherein blocking further includes using the SLM to actively block direct sunlight from reaching the imaging sensor.
14. The method as recited in claim 12 , wherein blocking further includes using the SLM to actively block counter measures.
15. The method as recited in claim 8 , wherein the method is performed outside of a calibration lab, after an undesired external stimulus to the imaging sensor compromises an initial calibration that was performed prior to the shock to the imaging sensor.