Design and evaluation of controls for drift, video gain, and color balance in spaceborne facsimile cameras
National Aeronautics and Space Administration, 1973 - Technology & Engineering - 29 pages
The facsimile camera is an optical-mechanical scanning device which has become an attractive candidate as an imaging system for planetary landers and rovers. This paper presents electronic techniques which permit the acquisition and reconstruction of high quality images with this device, even under varying lighting conditions. These techniques include a control for low frequency noise and drift, an automatic gain control, a pulse-duration light modulation scheme, and a relative spectral gain control. Taken together, these techniques allow the reconstruction of radiometrically accurate and properly balanced color images from facsimile camera video data. These techniques have been incorporated into a facsimile camera and reproduction system, and experimental results are presented for each technique and for the complete system.
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1/f noise 2N3820 FET switch acquisition and reconstruction angular resolution atmospheric transmittance automatic gain control automatic-gain control basic broad instantaneous field Burcher Circuit diagram COLOR BALANCE color channel color picture dark sample DC mode dc offsets detector drift amplitude drift signal drift-control circuit experimental results facsimile camera system facsimile camera video field of view filter gamma correction glow modulator tubes Glow tube high-pass filter imaging process imaging system Katzberg Langley facsimile camera Langley Research Center lens diameter light output line scan low-frequency noise Luna 9 Lunokhod mode of photodetector NASA TN nonlinear Optical-Mechanical Scanner photodetector operation photosensor aperture picture element planetary lander preamplifier output presents electronic techniques pulse radiant power falling radiometrically accurate relative spectral gain reproducer sample-and-hold circuit scene being imaged scene irradiance shown in figure silicon photodetector spectral gain control system for planetary tube current variations in scene VIDEO ACQUISITION ELECTRONICS video level video signal Viking lander camera voltage