Image intensifier t. v. fluoroscopy system

Claim 2

An image intensifier TV system comprising: an X-ray source for directing X-rays through a body; television pickup means including an image intensifier which receives X-rays which pass through said body and which produces an image therefrom, and camera means which provide a video signal from said image; display means which produce a display from said video signal and which include an automatic gain control function; negative feedback means having a closed loop which adjust target anode voltage and current applied to said X-ray source in response to the level of said video signal; and automatic control means which increases a loop gain of the closed loop if said target anode voltage exceeds a predetermined voltage.

Claim 3

A system as claimed in claim 1 including a variable gain factor device in series with the closed loop and means for increasing the gain factor of said device by an amount dependent upon the amount by which the anode voltage exceeds the predetermined voltage.

Claim 4

An image intensifier TV system comprising: an X-ray source for directing X-rays through a body; television pickup means including an image intensifier which receives X-rays which pass through said body and which produces an image therefrom and camera means which produce a video signal from said image; display means which produce a display image from said video signal and which include an automatic gain control function; negative feedback means including a closed loop having a variable gain function which adjust a target anode voltage and current applied to said X-ray source in response to the level of said video signals; and difference detector means which function to detect the difference between an exposure rate produced by said X-ray source and a predetermined exposure rate and which control the gain function to hold said gain function constant if the exposure rate of the source is less than or equal to the predetermined rate and to increase the gain function if the exposure rate of the source exceeds the predetermined rate.

Claim 5

An image intensifier TV system comprising: an X-ray source for directing X-rays through a body; television pickup means including an image intensifier which receives X-rays which pass through said body and which produces an image therefrom and camera means which produce a video signal from said image; display means which produce a display image from said video signal and which include an automatic gain control function; negative feedback means including a closed loop having a variable gain function which adjust a target anode voltage and current applied to said X-ray source in response to the level of said video signals; and difference detector means which function to detect the difference between an exposure rate produced by said X-ray source and a predetermined exposure rate and which control the gain function to hold said gain function constant if the exposure rate of the source is less than or equal to the predetermined rate and to increase the gain function if the exposure rate of the source exceeds the predetermined rate.

Claim 6

A system as claimed in claim 3 wherein the gain function of the device is increased proportionally to the amount by which the exposure rate of the source exceeds the predetermined rate.

Claim 7

A system as claimed in claim 3, wherein the variable gain function is substantially unity if the exposure rate of the source is equal to or less than the predetermined rate.

Claim 9

A system as claimed in claim 6, wherein the said maximum gain function is 2.

Claim 10

A system as claimed in claim 3, wherein the variable function includes a voltage-controlled amplifier.

Claim 11

A system as claimed in claim 8, wherein the difference detector means include a differential amplifier having a reference voltage source connected to one input thereof and a control voltage connected to a second input thereof, which control voltage serves to control the target anode voltage of the X-ray source.