X-ray or gamma ray systems or devices – Electronic circuit – Exposure timer
Patent
1987-01-22
1987-10-27
Church, Craig E.
X-ray or gamma ray systems or devices
Electronic circuit
Exposure timer
378108, 378109, 378110, 378111, 378112, 378114, 378115, 378116, 358111, 340347DD, H05G 164
Patent
active
047034963
ABSTRACT:
A voltage signal proportional to the brightness of an x-ray image is derived. In a mA loop the ratio of a reference voltage to brightness is determined. If the brightness ratio does not equal 1 it causes the x-ray tube current controller to adjust current (mA) to eliminate the error. A command proportionate to the ratio is stored until the next image frame. In a kV loop a ratio of the last mA command and a set limit for mA is taken. This error ratio is multiplied by the brightness ratio to provide a kV control ratio indicative of how much of the brightness error the kV loop is obliged to correct. The kV control ratio is corrected for nonlinearity between kV change and brightness change and the resulting command is used to adjust the kV applied to the x-ray tube anode. In a video gain control loop a ratio is taken between the stored last brightness ratio or mA command and maximum mA command limit and the brightness change resulting from the last kV control command is ratioed to the maximum brightness factor limit. The result of multiplying the last two mentioned ratios and the brightness ratio is the new video gain (VG) control signal. The VG signal is used to adjust the f-stop of the video camera and the electronic gain to change brightness.
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patent: 3894235 (1975-07-01), Franke
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patent: 4361901 (1982-11-01), Daniels et al.
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patent: 4553255 (1985-11-01), Kanerva
patent: 4573183 (1986-02-01), Relihan
patent: 4590603 (1986-05-01), Relihan et al.
patent: 4593371 (1986-06-01), Grajewski
Meccariello Thomas V.
Relihan Gary F.
Church Craig E.
Freeman John C.
General Electric Company
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