The principle and the experimentation of a new MTF measuring technique based on the multislit-scanning method have been described. In order to improve the signal-to-noise ratio in the measured transfer function, a line image is scanned stepwise by a multislit having a pseudo-random transmission characteristic determined by the Nelson-Fredman matrix, which performs an adequate encoding on the noise generated in the photo-electric measurement process. The method proposed has been compared experimentally with the conventional knife edge scanning method. It has been found that the multislit-scanning method can reduce effectively the influence of noise that is independent of the signal intensity.

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According to the van Cittert-Zernike theorem, the distribution of the degree of coherence on a plane illuminated by an incoherent grating-like source is similar to that of the amplitude of the Fraunhofer diffraction pattern which is produced by a diffraction grating of the same size and shape illuminated coherently. To verify this experimentally, double-slits of various separation are illuminated by a grating-like source, and the visibility of Young's interference fringes formed behind the double-slit is measured photographically. The presence of the periodic maxima and the small secondary maxima of the degree of coherence is confirmed, and, in general, experimental values are in good agreement with the theoretical prediction.

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The relative advancement of colored surfaces is studied analytically with an assumption that this phenomenon is caused by small change in convergence of binocular sight introduced by the color. Proportional relation of the relative advancement to square of the observation distance is predicted from the assumption and confirmed by the experiments.
Existence of sight deflection of single eye vision is predicted from the results, which is verified by experiments. The experimental results of sight deflection showed good quantitative agreement with that of relative advancement.

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The time interval distribution of photoelectric pulses, that obey the statistics of Gaussian-Lorentzian light, is derived under the condition of stationary Markov process and the expression of this distribution involves the parameter of correlation factor, the value of which is less than unity in real experiments. The spectral linewidth of very weak light is determined by using the distribution.

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An economical method is proposed for computing optical transfer functions with relatively small computers. The method is based on the practical view that the transfer functions in the radial and tangential directions provide the necessary and sufficient information for the evaluation of usual lenses, and by the use of the symmetry of the pupil function the requirement of large amounts of computer memories is alleviated and still the faster calculation is achieved. The validity of the method is confirmed by performing test calculations and comparing the required time and memories with those spent in the same calculations by the conventional double-transform method. Theoretical considerations are given to the maximum aberration for which the transfer function can be computed with sufficient accuracy, and the characteristics of errors introduced by the aberrations exceeding this criterion are also investigated. The theory is verified by numerical experiments.

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