CONTRAST INCREASING BY 3RD-ORDER NONLINEAR IMAGE-PROCESSING - A NUMERICAL STUDY FOR MICROSCOPIC RECTANGULAR OBJECTS

This study deals with the simulation of the image formation involved b y using a nonlinear image processor composed of a nonlinear medium pla ced at the common focus of a 4-f system. A simple linear model is deve loped taking into account the third-order optical nonlinearity of the medium (in the general case of nonlinear absorption and dephasing) and the optical transfer function of the 4-f system. The simulated images through the system are given for phase and/or amplitude rectangular o bjects. Our model and its corresponding simulation lead to optimizing nonlinear parameters of the medium for this class of objects, whatever their transmittance is, in order to enhance the visibility in image p rocessors. (C) 1998 Elsevier Science B.V. All rights reserved.