PURPOSE: To stably execute switching operation even if response time is changed due to temperature change by receiving light beams radiated to liquid crystal to detect the switching of the liquid crystal and controlling a liquid crystal driving signal outputted from a driving means on the basis of the detecting signal and a liquid crystal driving signal outputted from a liquid crystal driving means.

CONSTITUTION: The image of an object is transmitted through an optical system 1 and a liquid crystal shutter 2 and converted into a video signal by a solid image pickup element 3. Light beams emitted from a liquid emitter 4 and passed through the liquid crystal are received by a light receiver 7, a signal corresponding to switching is amplified by an amplifier 8, a difference between the level V1 of an input signal SO and a reference voltage is amplified at the trailing edge of a vertically synchronizing signal VD coincident with the vertical transfer period of the element 3 and outputted to control delay time (namely closed driving time tD from the leading edge of a liquid crystal switching start time signal VD) from the VD by a control circuit 11. A negative peak of an output signal from an amplifier 8 is detected by a negative peak detector 10 and a closing drive time of the liquid crystal 2 is controlled by the circuit 11. The circuit 11 outputs a switch driving signal SCO synchronizing with the signal VD based on the output of the comparator and a negative peak detecting output to convert the level of a driving circuit 12 and to drive the liquid crystal. Said constitution makes it possible to switch the liquid crystal stably.