Table of contents

Several methods for optical comparison or characterization of threedimensional object forms are presented. By generalizing the classical techniques of production of image differences it is possible to obtain informations of differences in a threedimensional manner. The classical techniques only contain two dimensional information. The methods are based on appropriate fringe projection systems on the object.

A simple characterization of an object is the use of contour lines. Different methods of contour lining are shown, especially in real time.

In all these methods the production of Moiré fringes play an important role. These fringes permit the determination of differences between two objects and the plotting of contour lines, too.

We present a rigorous formalism for the study of the diffraction by a grating of finite conductivity, possibly covered with a thin film. This diffraction problem is reduced to the numerical boundary-value problem of integrating a set of differential equations. A detailed experimental verification of the theory is presented, for the two fundamental cases of polarization. Specific applications of the method are given, such as the influence of conducting or dielectric layers on gratings. These should prove particularly interesting to opticians in the ultraviolet.

A new interferometer has been developed which can be used both for analysing the homogeneity of I. R. materials and for inspecting the wave-form emerging out from an optical system. This new type of interferometer utilises a diffraction grating as a beam divider and further permits an important variation in the fringe contrast to be obtained for a given blaze angle by the variation of the efficacity of the grating with the orientation of the plane of polarisation. This improvement permits the compensation of photometric losses due either to an absorbing material or due to a highly reflecting material, that may be under test. By this way it is possible to evaluate all materials within a transmission range from 10% to 100%.

This interferometer functions at 10.6μm. Results obtained are detailed here in.

The polarized light scattered from a plane parallel atmosphere is considered. Computations are made, for a normal incident beam, using the Kuscer's generalised « Spherical Harmonics » method, in its exact form, and also using a successive approximations scheme. This last technique gives some insight about the formation of the scattered light. It is confirmed that the polarized part of the emergent radiation comes from a thin upper atmospheric layer, but this polarized light seems generated quite independently of the global radiation field.

After a short description of the principle of dye laser, the new technology using jet stream is given. Advantages compared with traditional technology are discussed. Results obtained are given.

This paper presents the theoretical hypothesis by which grinding and polishing of optical glass surfaces has been explained by several authors.