Radiant energy – Photocells; circuits and apparatus – Photocell controlled circuit
Patent
1990-06-21
1991-10-08
Nelms, David C.
Radiant energy
Photocells; circuits and apparatus
Photocell controlled circuit
35821331, H01J 4014
Patent
active
050556673
ABSTRACT:
A method of controlling the dynamic range of a CCD or similar device. The method is used in connection with a charge-coupled device or like structure of known construction having a photogate region in which charge is generated at a rate proportional to the intensity of incident electromagnetic radiation. The photogate accumulates charge during a predetermined exposure period. A sink region is disposed to receive excess charge from the photogate region, and the passage of charge from the photogate region to the sink region is controlled by a control gate of the type commonly used for integration control. A second gated region is present for receiving charge from the photogate region for transporting charge therefrom. A potential is applied to the control gate which has a magnitude causing all charge above a certain charge clipping level in the photogate region to pass to the sink region, and the magnitude of the potential is caused to vary during the exposure period according to a predetermined function, which may be a non-linear function such as logarithmic. In this way the clipping level varies according to the predetermined function in real time during the exposure period. The total charge accumulated in the photogate region, limited according to the predetermined function, is then transferred to the second gated region at the end of the exposure period.
REFERENCES:
patent: 4845566 (1989-07-01), Sakai et al.
patent: 4849814 (1989-07-01), Van De Steeg
Loral Fairchild Corporation
Nelms David C.
Shami K.
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