Charge coupled device focal zoom

Abstract

The charge coupled device focal zoom of the present invention is used in connection with a time delay and integration charge coupled device imager in which a plurality of detectors is scanned at an angular rate .omega. across a field of view subtended by a scanning angle .alpha., wherein output charge from the detector array is clocked through associated charge coupled device registers at a clock frequency f.sub.ccd in synchronism with the scanning motion. A video display receiving the signal from the charge coupled device register may zoom in on a small portion of the field of view subtended by a reduced angle .alpha./n. This is accomplished by restricting the scanning angle to the reduced angle .alpha./n and simultaneously reducing the CCD clocking frequency to f.sub.ccd /n and the scanning rate to .omega./n. The resolution of the image is enhanced because the sampling time T is increased while at the same time the synchronism between charge transfer and scanning movement is maintained for all values of n. A frequency converter is provided at the output of the serial registers which periodically integrates output charge packets from the registers at a constant rate so that a video signal having a constant frequency is output to video display electronics even though the zoom magnification factor n is varied.