INTENSITY-TO-SPATIAL FREQUENCY TRANSFORMATIONS IN OPTICAL SIGNAL-PROCESSING

Abstract. Intensity-to-spatial frequency transformations can be exploited for a variety of useful optical information processing operations. Resolution elements of an image are encoded with a grating structure whose spatial frequency and/or orientation is a function of the local image intensity. Assuming that certain sampling requirements are met, each intensity level is assigned to a different point in Fourier space. Various schemes of spatial filtering can then be used to alter the relative intensity levels. The procedure can be used for nonlinear analog point transformations and for numerical processing using binary or residue arithmetic. Theta modulation and frequency modulation are special cases of the technique. Off-line methods for implementing intensity-to-spatial frequency transformations include halftoning and grating techniques; real-time methods include new electro-optical systems such as the variable-grating-mode (VGM) liquid crystal devices. Details of these devices and experimental results are presented.© (1984) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.