Low level processing or preprocessing is often the starting point in many computer vision systems. This stage is typically characterized as picture processing and uses gradients, edge templates, filters, thresholding, and other enhancement techniques. The next stage in computer vision commonly deals with the processed image, usually binary in nature, and extracts intrinsic features such as size, shape, boundary, orientation, moments, etc. A new class of multiple-valued integrated optical processors is proposed for the parallel implementation of selected preprocessing algorithms. The basic component of the multiple-valued processor is an integrated optical threshold gate.(1-3) The parallel processing algorithms required for both smoothing and boundary determination with an integrated optical thresholding array are described. One possible architecture for an optical parallel digital image processor is presented.© (1985) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.