A STATISTICAL EXPLANATION OF THE EFFECT OF LUMINANCE ON PHOTOPIC VISUAL-ACUITY OF SPECKLED IMAGES

The intensity of a polarized speckle pattern obeys a negative exponent ial probability density function. This probability distribution implie s a signal-to-noise ratio, SIN, unity since the standard deviation equ als the mean intensity. However, when the logarithmic response of the retinal photoreceptors is considered, the first-order statistics of th e pattern is transformed in such a way that S/N ratio becomes a functi on of the mean intensity. This theory is closely connected with the ma sking effect of speckle in experiments of vision. In particular, it co ntributes to explain why in photopic vision of speckled images the res olving power of the visual system decreases as the mean luminance incr eases.