Application of a charge-injected device (CID) camera system for collimated beam angle measurements

David W. Perkes; Dave Higham; V. Alan Thurgood

doi:10.1117/12.185832

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14 September 1994 Application of a charge-injected device (CID) camera system for collimated beam angle measurements

David W. Perkes, Dave Higham, V. Alan Thurgood

Proceedings Volume 2268, Infrared Spaceborne Remote Sensing II; (1994) https://doi.org/10.1117/12.185832
Event: SPIE's 1994 International Symposium on Optics, Imaging, and Instrumentation, 1994, San Diego, CA, United States

Abstract

The calibration of low background IR sensor systems require cryogenically cooled collimators. The need to characterize the output beam angle as a function of pointing position, cryogenic pressure, temperature and liquid level has always been difficult. Historically, manual theodolites have been used to measure these parameters. Because accuracy and repeatability of the manual measurement device is dependent upon user interpretation and manual coupling, the ability to measure small drifts with the thoedolite is not sufficient. The time required to manually characterize the output beam angle as a function of pointing position is so long that the drift of the beam angle begins to dominate the measurement error. A Charge Injection Device (CID) camera with very uniform focal plane pixel spacing and quality optics, can be used to very accurately monitor output beam angles in short intervals. This is accomplished by using sub-pixel centroiding techniques. Resolving a reimaged spot to 1/40 pixel accuracy is accomplished by using a weighted center of area calculation. Automated measurements have two advantages: they are faster, allowing for large numbers of measurements and higher resolution as well as removing human error, resulting in a better understanding of the pointing system. Using a 512 X 512 CID camera, angular resolution of 5 (mu) rad is achieved for a field of view of 6 degrees full angle. The potential for absolute accuracies of the same resolution is achievable if the stability and nonuniformities of the CID camera and optics are calibrated. Typical results obtained from a cryogenic system taken with the CID camera will be presented.

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David W. Perkes, Dave Higham, and V. Alan Thurgood "Application of a charge-injected device (CID) camera system for collimated beam angle measurements", Proc. SPIE 2268, Infrared Spaceborne Remote Sensing II, (14 September 1994); https://doi.org/10.1117/12.185832

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