Abstract: An apparatus for effecting spatial Fourier transform spectroscopic detection of light from a surface luminescent object with high sensitivity by use of a quadrangular common path interferometer. The apparatus includes an improvement which consists of an additional imaging optical system which converges a light beam from the specimen so as to enter the beam splitter. The additional imaging optical system is disposed so that an image position is substantially coincident with the position of the second of three mirrors in the apparatus.

Abstract: In the method of and apparatus for measuring a spectral absorption in an opaque specimen, a scattering specimen is illuminated with highly directional light of variable wavelength from a specific direction, thereby removing scattered rays as much as possible, and thus detecting the intensity of only parallel rays of a component transmitted or reflected in a specific direction (i.e., rectilinear component rays) by use of a highly directional detecting system, for example, a heterodyne light-receiving system, Michelson light-receiving system, highly directional optical system, etc. It is therefore possible to measure spectral absorption characteristics of a scattering specimen with high accuracy without picking up scattered light in other undesired directions nor other noise light. In addition, the measurement of the control is exceedingly simplified in comparison to the conventional method and thus the measurement is extremely facilitated.

Abstract: A light propagation region is divided into a plurality of subregions, each subregion being limited within a minimum spatial resolution unit where an interference occurs between discrete points, and a 0-order diffraction pattern of a Fraunhofer diffraction image is detected If a convex lens and either a pinhole or an optical fiber which is disposed on a focal plane of the convex lens are employed and the diameter of the pinhole or the core diameter of the optical fiber is set to be not greater than the first dark ring of a Fraunhofer diffraction image produced by the convex lens, it is possible to take out the greater part of the energy of a plane wave component that enters the lens from a predetermined direction and remove other components from different directions, i.e., scattering component. If a plurality of optical systems of this type are bundled together, only a plane wave with a one- or two-dimensional intensity distribution can be taken out with high brightness and high resolving power.