Characteristics of a model retinal receptor studied at microwave frequencies.

A simplified microwave model of the human eye was constructed in order to study the characteristics of a model retinal receptor. A technique devised by O’Brien was employed. The model receptor was a truncated cone of polystyrene-foam. This was fitted into a horn which transmitted the energy to a detection unit. The relative sensitivity of the model receptor was determined when it was irradiated by a point source and when it was placed at several different positions in a diffraction pattern at or near the Gaussian image point. The directional sensitivity was studied by pointing it in different directions. In addition, interaction effects between neighboring receptors were studied. Two different wavelengths have been used.It was found that there were differences in energy absorbed by the detector unit when the model was irradiated by the point source and when it was placed in the Fraunhofer diffraction pattern. More energy was absorbed when a shorter wavelength was employed. It was found that the model antenna became more efficient as it was moved away from the center of the diffraction pattern. The direction of maximum sensitivity shifted as a function of the position of the model antenna in the diffraction pattern. Markedly different directional sensitivity patterns were obtained for different physical distributions, for different positions in those distributions, and for different wavelengths.There was essentially no interaction between two neighboring receptors if their axes were kept parallel. Interaction did occur if the tapering sides were brought into contact or near contact. The implications of these findings are discussed.