A study has been made of the transmission characteristics of a Fabry-Perot interferometer as modified by the asymmetric surface defects present on the plates. Asymmetric line profiles can be obtained if the error in the plates is not symmetrically distributed about the mean planes of the plates. Peak irradiance and shift of fringe from its integral order position have been tabulated. Such investigations are of interest in a number of problems in high resolution spectroscopy.

The detection and resolution of an object, and an estimation of its parameters, such as position and radius, have been treated by signal detection theory. The object was viewed through an optical system that had a circular diaphragm and which suffered from spherical aberration and defect of focus. It was observed that the detectability, resolution, and accuracy in the determination of the parameters decreased with an increase in the aberration coefficient, though the decreases were smaller for partially coherent light than for coherent light.

Theoretical investigations have been made for the Fraunhofer diffraction pattern of an annular aperture in the turbulent medium. It has been shown that by increasing the obstruction ratio, the central maximum sharpens but the intensity of secondary maxima increases. Curves for efficiency have been drawn for Gaussian and thermodynamic models for refractive index fluctuations in the medium. Curves for half width at half height have also been plotted.

The focusing properties of an aberration free defocused optical system with a slit aperture have been investigated in the case of quasimonochromatic partially space coherent light. The point spread function has been plotted for sinc and gaussian forms of the mutual coherence function. In certain cases, partially coherent illumination results in an improved performance of the system.

Far-field intensity distribution has been plotted for a circular aperture suffering from spherical aberration and illuminated by quasi-monochromatic partially space-coherent light. Gaussian and besinc forms of correlation have been assumed. It is shown that higher values of coefficient of aberration can be tolerated as the value of number of correlation intervals contained in the aperture increases.

Fraunhofer diffraction patterns produced by a circular aperture suffering from spherical aberration and illuminated by partially coherent light are presented. Improvement in the images has also been shown when an appropriate amplitude filter is used. Tolerances for the value of the coefficient of aberration based on the Strehl criterion have been calculated for various values of correlation intervals contained in the aperture. Two forms of mutual coherence function and four values of aberration coefficient have been assumed.

Diffraction of partially space coherent light by a slit-aperture with an apodizing filter has been examined theoretically. Results have been presented for the irradiance distribution in the Fraunhoffer diffraction images for exponential and sinc forms of correlation of vibrations across the diffracting aperture. Tolerance and apodization coefficients have been calculated for the number of correlation intervals contained in the aperture, for the various values of the amplitude filter-parameter.

Fraunhofer diffraction patterns produced by a narrow rectangular aperture having a non-uniform illumination with partially coherent light are presented. Graphs of intensity distributions in the diffraction patterns for three cases of amplitude filters and four forms of the mutual coherence at the slit are given. An increase in the half-width at half-height (H.W.H.H.) and a decrease in the intensity at the centre are observed. Tolerances for the value of the correlation interval in the aperture based on the Strehl intensity criterion have been calculated for various amplitude filters.

The effect on photometric-setting accuracy of mechanical misalignments and surface errors of the end mirrors of a double-passed Michelson interferometer has been analyzed. Tolerance limits are given for the mirror quality and their misalignments.