Minimal angle of resolution in monocular, single-colour vision and the TAIS model.

The mathematical model TAIS simulates visual perception of single-colour or black-and-white, non-moving objects. It makes an analysis of the luminance spatial distribution in an optional direction and describes it in linguistic terms. The model comprises three modules that successively convolve the luminance distribution with a spatial filter (a normalized Gaussian function), calculate the second derivative of the convolution and, with use of context-free and context-sensitive grammars, generate a string of symbols. The string of symbols contains the information, simplified in form and rectified from visual noise, about perceived spatial changes of brightness. The model simulates various visual phenomena, e.g. edge detection and spatial resolution, and it predicts the resolving power dependence on the light source size. The model-generated dependence of minimal angle of resolution on the light source width fits the experimental data with linear correlation coefficients in the range 0.70-0.94. The diagram consists of decreasing and constant parts, its shape adjusted to experimental data through selection of the Gaussian filter parameter and second derivative threshold.