Highly sensitive image pickup apparatus

Abstract

This image pickup apparatus is capable of picking up very low level images, such as a star or a comet in a night sky, and is capable of obtaining a video signal having a desired S/N ratio without using a conventional noise reducer. The apparatus comprises a television camera including an image pickup tube, a field memory for storing a video signal delivered from the television camera, and a write-inhibiting control circuit, wherein a period of beam scanning for generating the video signal in the image pickup tube is extended to n-times the standard field period for increasing the sensitivity of the image pickup tube. Writing to the field memory is inhibited in other periods except for the beam scanning period, while a normal television signal is continuously obtained from the field memory. A key signal corresponding to dark portions of the image that are not to be enhanced may be generated and stored in an area memory, and then read out from the area memory during every standard field period. An imaging control circuit responsive to the imaging control signal and the key signal then controls the image pickup device, such that it extracts a videeo signal from the whole of an imaging area during the period of one field designated by the imaging control signal, and extracts a video signal from a partial area apecified by the key signal during other field periods.