Abstract

We have shown that the use of a nonlinear material as a Fourier filter in the common focus of two lenses in a 4 f setup allows all optical image processing (Fig. 1).^1,2 The measurement of the nonlinear changes undergone by the image of an object in this setup can be used to characterize the nonlinear response of the Fourier filter.³ The method has been developed to measure the real and imaginary parts of X³ under picosecond excitation in various materials (liquids and crystals). It can be summarized as follows: f or an object 0(x,y), nonlinear image I (x,y) is recorded on a calibrated CCD camera, and compared with the calculated image I_c (x,y). The calculation of Ic (x,y) is made (analytically or numerically according to the choice of the object) using the following scheme:

© 1994 IEEE