Image Differentiation with the Aid of a Phase Knife

摘要

A scheme for optical differentiation of images based on spatial filtering is proposed. A phase knife-a glass plate consisting of two halves, whose thicknesses are chosen so that the optical path difference between the light waves passed through them makes up half the wavelength-serves as a filter. The linearity of the transformation and the sensitivity of the system of noise are investigated theoretically. The scheme was experimentally implemented on the basis of a liquid-crystal light valve. The experimental results confirm that such a setup can be efficiently used for processing images with a narrow-band spatial spectrum and for visualization of phase objects.