Images of Periodic Objects under Partially Coherent Illumination

Abstract

The imagery of periodic objects under partially coherent illumination by an optical system employing an annular condenser for illumination has been considered. The problem has been studied in terms of the generalized cross transfer functions and the results have been discussed in terms of the contrasts in the images of periodic objects commonly employed, namely the sine wave, rectangular wave and triangular wave objects. It has been shown that the effect of using a central obscuration on the condenser of the illuminating system is to improve the response of the system at higher spatial frequencies with a corresponding reduction in the response at lower spatial frequencies. The irradiance distribution in the images of these objects have also been discussed and some interesting features have been brought out