Determination of the transfer function of an optical system by means of a random distribution of transmittance

The described analogical method allows to visualize and determine the Transfer Function of any optical system from an object distribution of random transparency of which the statistical properties are stationary. This method consists in obtaining the image of the transparency in spatially incoherent light by means of the optical system under test. This amounts to substitute an infinity of sources distributed randomly in a plane for the generally used point source. The Fourier Transform of this image provides an amplitude distribution proportional to the desired function. Moreover the information contained in the image allows to study the variations of the transmission properties according to the parameters acting in the image process. Experimental results connected with different complex optical systems and more particularly with synthetic apertures are presented.