A mathematical model of visual system of the human observing images on optoelectronic device display is proposed. The model allows to formalize in linear approximation the physiological processes of registration and transformation of halftone object images in the human visual system in the presence of external and internal noise, and to estimate the detection probability of objects visual images in the form of Johnson’s equivalent bar patterns. On the basis of proposed model mathematical expressions for the visual system contrast sensitivity function are derived. Experimental studies on the measurement of this characteristic are carried out. A satisfactory agreement between the calculated and experimental results indicates the adequacy of the proposed mathematical model for the accepted restrictions on its applicability.