Effect on the Spatial Frequency Contents of the Object of Reducing Speckle in Partially Coherent Illumination

Abstract

Effect of speckle reduction on the spatial frequency contents of the object is investigated for partially coherent optical systems specified with the circular and ring effective sources. For this purpose, using the general formula derived previously, the spatial frequency distributions of the noise power of speckling are given and the general formula to obtain the image contrast of the sinusoidal object in any illumination mode, is derived. Computer simulations are made to obtain images of simple object models in the presence of the random phase noise under the stated coherence conditions. The correspondence between the statistical evaluation of the speckle noise and the appearance of the image is examined in coherent and partially coherent optical systems. Then, some experimental results for the practical optical systems are compared with corresponding, simulated images.