Die abbildungseigenschaften der augenmedien

Abstract

The optical image produced by the human eye was investigated. For this purpose a point source was focused on the retina, and the light distribution which left the eye after reflection from the retina was analysed. This method is open to the criticism that the scattered light from the refracting surfaces and the inhomogeneities of the optical media of the eye may impair the results. Therefore, preliminary investigations with animal eyes were necessary. The comparision of the results, obtained with these eyes, with the light distribution measured directly in the retina plane, showed that the influence of the scattered light in the living eye may be neglected. The imaging properties of human eyes were measured in the form of the contrast transfer function. By means of an analytical approximation of the results, the spread functions of point and line on the retina were calculated. Measurements with several persons gave a mean point spread function which may be described by−1.17r, whereis the relative luminance in the point image as a function of the radiusin minutes of arc. The dependence of the transfer function on the angle against the optical axis and on the diameter of the pupil were measured. The point and line spread functions which were calculated from the measured transfer functions provide an easy explanation of the minimum separable for points and lines and vernier acuity. The contrast threshold of small circular objects as a function of diameter is explained quantitatively by the contrast loss in the optical image.