Pick-up and/or display device, and an imaging system comprising such a device.

摘要

A pick-up and/or display device comprises a memory in which a video signal is written at a write frequency under the control of a clock and is read therefrom at a read frequency. Image expansion or image compression can thus be realised. The clock, a clock input of which is connected to a synchronizing pulse generator, comprises an oscillator having an adjustable frequency, an oscillator output constituting a clock output and being connected to a frequency divider whose output signal is applied to an integrating comparator circuit, an output signal variation of which is proportional to a difference between a mean input signal and a predetermined reference voltage, the comparator circuit being connected to a frequency set input of the oscillator, the oscillator comprising a trigger input which serves to switch the oscillator on and off and which constitutes the clock input. A clock of this kind exhibits an accurate phase relationship with the synchronizing signal which is not subject to temperature drift and noise. The frequency of the clock can be accurately adjusted by adjustment of the reference voltage. <IMAGE>