A special purpose hardware for high speed Fourier transform/convolution has been developed. The features of the hardware are that it can execute Fourier transform, convolution, and complex multiplication in high speed and each of three functions can be used properly. This hardware is equipped in the digital image processing system using a minicomputer. Utility of the hardware is shown by economy of the processing time of the two dimensional Fourier transform and image restoration in the space domain. A technique to obtain the digital filter suited for image restoration in the space domain is described, and some experimental results are demonstrated.
One-beam-mode laser Doppler velocimeters are analysed for two different types of optical systems. The effects of the detection optical systems on the beat signals are discussed in two limiting cases of very low and high concentration of the scattering particles. The discussion clarifies that the measuring volume in the case of high particle concentration is different from that in the low concentration case. Coherence condition is found to be equivalent to the condition that the size of the pinhole on the detection surface is smaller than the size of speckles on that surface.