X-ray or gamma ray systems or devices – Electronic circuit – Exposure timer
Patent
1990-04-06
1991-03-26
Westin, Edward P.
X-ray or gamma ray systems or devices
Electronic circuit
Exposure timer
378 97, 378108, 378109, 378111, H05G 164, H05G 144
Patent
active
050035720
ABSTRACT:
The brightness of an X-ray video image during fluorography is maintained at a substantially constant level by a control circuit which varies the X-ray dose in relation to changes in the average brightness of the X-ray image. As the X-ray system approaches the limits of its imaging capability, varying the X-ray dose alone may not yield the desired brightness level. At this point, the gain applied to the video signal is increased to improve the brightness. A linear brightness taper function is used such that, as the level of video gain required to maintain constant brightness increases, the actual video gain increases by a smaller proportional amount. This function results in the brightness of the video image decreasing somewhat as the video gain is required to provide a greater degree of brightness compensation. This reduction in brightness not only provides a visual indication to the image observer that the system is approaching the imaging limits, but also creates an illusion that noise artifacts in the image are not intensifying as the video gain increases.
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Belanger Barry F.
Meccariello Thomas V.
Chu Kim-Kwok
General Electric Company
Westin Edward P.
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