This paper presents a review of the theoretical analyses and experimental characterizations of the Itek PROM (Pockels Read-out Optical Modulator). The basic operational principles are discussed, followed by a theoretical description of the dependence of PROM characteristics on fabrication and operational parameters. An extensive section with the results of various characterization programs is provided. Of particular interest are resolution and diffraction efficiency experiments. A discussion of PROM fabrication techniques, materials, and design, both present and future, is included. Finally, examples of some of the many applications for which the PROM may be used are given. Applications include: incoherent image enhancement, image or signal correlation, real-time spatial filter generation, and two-dimensional logical operations.