Abstract: The effect of the aspect ratio change of target images on the distortion tolerance of matched filter and output correlation peak value is analyzed when VLC is used for the optical correlation recognition according to the diffraction theory. The matched filter was designed with the algorithm for the unconstrained phasematched-only filter and the method of the detour phase coding. The optical correlation recognition was carried out to the rectangular targets whose area and transmissivity are fixed but the length-width ratio is different. The simulated and tested results show that the image symmetry becomes better, the distortion tolerance of matched filter and the correlation peak value are decreased with the increase of the aspect ratio of the target image, and VLC is easier to recognize the target image whose aspect ratio approaches to 1.