Automatic diaphragm control device for use with CCTV camera

Claim 1

A remote-controllable automatic diaphragm control device for use with a CCTV camera including not only automatic diaphragm control means adapted for diaphragm control utilizing a video signal coming from a television camera but also remote diaphragm control means adapted for electrical adjustment of the diaphragm to a desired diaphragm position independently of said video signal, said diaphragm control device comprising: a driver circuit adapted to drive a diaphragm drive motor to open and close the diaphragm; an automatic control circuit to apply said driver circuit with a control signal based on the video signal coming from the television camera; first means provided in said automatic control circuit for continuous control of the video signal with respect to an absolute brightness of an object to be picked up; second means provided in said automatic control circuit for continuous control of a proportion of the video signal corresponding to a bright area in the whole picture when a ratio of the bright area to a dark area of this object is relatively high; a remote control circuit to apply said driver circuit with a diaphragm position control signal exclusively for the remote diaphragm control; a position feedback circuit to detect a position to which the diaphragm has been driven by the diaphragm drive motor and thereby to electrically fix the diaphragm; a switching circuit for selective connection of said automatic control circuit or said remote control circuit to said driver circuit depending on the position control signal applied to said remote control circuit whether it is higher or lower than a predetermined reference voltage and further for connection of said position feedback circuit to the driver circuit only when said driver circuit is connected to the remote control circuit; and a stabilizer for stabilization of a control signal obtained by said automatic diaphragm control means and a detection signal fed back from a position detector element in said remote diaphragm control means with respect to a source voltage so that the diaphragm value once adjusted under a given source voltage may be held constant.