Low light level television camera

Claim 2

A low light-level television camera capable of operating over a wide range of input light levels and comprising: a cascaded gateable image intensifier and vidicon; means for generating an average signal level output from the vidicon; means responsive to said vidicon average signal output for generating a stepped gain control corrective signal; power supplies associated with said image intensifier and vidicon, said power supplies having means for providing stepped gain voltage change to the image intensifier and vidicon in response to said corrective signal, thereby providing wide range coarse gain control; and means responsive to a signal indicative of said stepped voltage change and to the average signal level output for producing a variable pulse width signal input to saId gateable image intensifier, whereby wide range fine gain control of said camera is obtained.

Claim 3

The device according to claim 1 wherein said means for generating an average signal level output comprises a video integrator; and said means for generating a corrective signal comprises a minimum/maximum level detector circuit, an up/down counter and decoder logic circuitry generating said corrective signal.

Claim 4

The device according to claim 2 wherein the means for producing a variable pulse width signal comprises a pulse width modulator and a high voltage pulse generator.

Claim 5

The device according to claim 3 wherein a vertical blanking signal provides timing signals to said pulse width modulator and said up/down counter circuit.

Claim 6

An automatic gain control system for a low light level television camera having a gateable image intensifier, a vidicon and power supplies associated therewith and comprising: means responsive to the vidicon output for generating an average signal level; comparator means for comparing said average signal level with a desired signal level range and for providing corrective signal outputs; decoder means responsive to said corrective signal output for providing a control output to said power supplies for changing the voltages thereof in stepped increments thereby obtaining coarse gain control; and pulse width modulator means simultaneously responsive to the control output from the decoder and to the average signal level from the vidicon for generating a pulse width control signal for a pulse generator operating said gateable image intensifier, whereby the pulse width variations provide fine gain control.

Claim 7

An automatic gain control system for a low light level television camera having a gateable image intensifier, a vidicon and power supplies associated therewith and comprising: means responsive to the vidicon output for generating an average signal level; comparator means for comparing said average signal level with a desired signal level range and for providing corrective signal outputs; decoder means responsive to said corrective signal output for providing a control output to said power supplies for changing the voltages thereof in stepped increments thereby obtaining coarse gain control; and pulse width modulator means simultaneously responsive to the control output from the decoder and to the average signal level from the vidicon for generating a pulse width control signal for a pulse generator operating said gateable image intensifier, whereby the pulse width variations provide fine gain control.