High-precision image motion measurement applied for space camera based on hybrid opto-digital joint transform correlator

Hybrid opto-digital joint transform correlator (HODJTC) is effective for image motion measurement, but it is different from the traditional joint transform correlator (JTC) because it only has one process of optical Fourier transform and the intermediate joint power spectrum (JPS) is directly input to a digital unit to compute the image motion. In original HODJTC, the correlation image is obtained by using a global discrete Fourier transform operator. In fact, the location of cross-correlation peak corresponding to zero image motion is known and the maximum image shift can also be estimated. Thus, the local cross-correlation image can be directly obtained by adopting a local Fourier transform operator instead. With the pixel-level location of cross-correlation peak is obtained, the up-sampling technique is introduced to relocate the peak in even higher accuracy. Both the experiments and simulations demonstrate that the RMS (root-mean-square) error of motion determination can be controlled below 0.05 pixels, which is a very promising result for real application.