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8.γ校正电路 (1)需要γ校正的原因在x线影象增强器电视中,信号的传输经过四次转换:射线强弱的变化转换为增强器输出屏荧光亮度的变化,荧光亮度的变化转换为电信号大小的变化,视频小信号转换为视频大信号,电信号的大小变化转换为显象管荧光屏黑白亮度的变化。若这些变化或转换过程都是线性的,那么显象管荧光屏上就能重现原始图象各点间存在的灰度比。设B_1为通过人体后射线图象的强度,B_3为显象管上图象的亮度,则: B_3=KB_1~γ式中K为比例常数。当γ=1时,B_1与B_3成正比。但若γ≠1,B_1与B_3不成正比,于是电视图象就不能正确重现被透照人体各部分的灰度
8. γ correction circuit (1) The reason for the need for γ correction In the x-ray image intensifier TV, the signal transmission through the four conversion: changes in the intensity of the beam into the output of the intensifier output fluorescence brightness changes, fluorescence brightness Changes into the size of the electrical signal changes, small video signals into video signals, the size of the electrical signal into CRT screen black and white brightness changes. If these changes or transitions are linear, then the CRT screen will reproduce the gray scale of the original image. Let B_1 be the intensity of the radiographic image passing through the human body and B_3 be the brightness of the image on the tube. Then: B_3 = KB_1 ~ γ where K is the proportional constant. When γ = 1, B_1 is proportional to B_3. However, if γ ≠ 1, B_1 and B_3 are not proportional, so the TV image can not correctly reproduce the grayscale of all parts of the human body