ABSTRACT
This chapter discusses parallel analog optical computing, which is mostly related to Fourier optics. Two-dimensional (2-D) spectrum is obtained by optical Fourier transforming input signal and then modified by spatial frequency filter. The Fourier transforming ability of a lens makes Fourier transform of an input image and this enables us to perform spatial frequency filtering for 2-D images. If the lower frequency component is passed by a filter, the noise including the higher frequency component can be reduced. Such filter is called the low-pass filter. On the other hand, the filter which passes the higher frequency component is called the high-pass filter. The phase contrast filter, which transfers the phase distribution to the intensity, is used to image the phase object, e.g., semi-transparent biological samples. The method which changes the pupil function to improve the resolution higher than the perfect optical system is called the super resolution.
