Study and realization of adaptive sampling method for CCD signal

The phase of space remote-sensing camera CCD signal varies slightly with the temperature shift and the aging of devices. Especially in the field of high speed applications, the change of analog signal phase is non-negligible so that the sampling positions which are determined and programmed with traditional method are no longer suitable. So the SNR of image drops drastically and even in some worse cases images cannot be displayed normally. To solve the problems mentioned above, an adaptive adjustment method for sampling position of space camera CCD signal was proposed in this paper. With the proposed method, the real-time phase variation of CCD analog signal was monitored and the variation parameters of sampling position were calculated. With the calculated sampling position parameters, the circuit adjusted the phase of sampling clocks on line. The sampling position can remain in optimal state although the temperature varied in large range in the life span of the camera and the SNR of images kept high stably. Tests show that with this method, phase variation of less than 100 ps can be detected and the sampling positions keep in optimal state. So the method is effective and has a good application prospect in the field of high resolution remote sensing cameras.