CONTRAST SENSITIVITY OF THE VISUAL-SYSTEM IN SPECKLE IMAGERY

The contrast sensitivity function (CSF) of the whole visual system is determined with the use of coherent diffuse illumination. This functio n provides supplementary data about the effect of speckle on the abili ty of the visual system to perceive the spatial information contained in an image. The results show that speckle not only prevents perceptio n of the finest details (highest frequencies) but also reduces the vis ibility of lower frequencies (especially where contrast is low). The d ifference between the CSF's determined with and without speckle is qua ntitatively very important. And the ratio between the two CSF's is a m easure of the retinal ability to perceive contrast in the presence of speckle noise. The influence of the pupil size and luminance level on the CSF with speckle is studied and compared with the influence of the same parameters on the classical CSF.