1. An optical system for forming, from an object beam of electromagnetic radiation, a hologram characterized by selectively altered intensity of the components in the object beam, comprising: a nonlinear optical medium for selectively altering the intensity of components in an incident object beam; means for performing forward and inverse transform operations on incident beams of electromagnetic radiation; and means for (a) transmitting said object beam through the transform means to thereby direct the forward transform of said object beam onto the nonlinear optical medium and (b) simultaneously directing a reference beam of electromagnetic radiation onto the nonlinear optical medium to form a hologram of the object beam transform therein.