The thermal change in optical path length and linear thermal expansion were measured for 19 kinds of optical glass with the modified Fizeau-type interferometer. The apparatus and interferometer were designed by the authors as shown in Fig. 2. The equation to calculate the temperature coefficients of refractive index dn/dt was described, and dn/dt was determined by measuring at intervals of 20°C in the temperature range from -40°C to +80°C for 5 wavelengths. To illustrate the results, some of the data were presented and it was summarized that dn/dt rose with increasing temperature and decreasing wavelengths. In this experiment, all of results showed positive values and it was found that these values depend on chemical composition PbO. The additive property between dn/dt and chemical compositions was recognized.

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New film formation technologies are reviewed. By using high energy particles, new type of film deposition or synthesis of the compound material which could not be expected by a conventional thermal and a chemical methods could be realized. In this paper, a classification of film deposition from the view point of the kinetic energy, the present situation of film formation, and the trend and the future of the techniques are described.

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Both films of SnO₂ and In₂O₃ which possess excellent properties as transparent conductive films have been practically used in various industrial fields. Recently their demands are greatly increasing in the application to transparent electrodes of a liquid crystal panel display device and so on. The vacuum evaporation methods developed by the authors for manufacture of them have been mainly utilized for their industrial production in our country, having some features preferable to other existing ones. In this paper those techniques are described concerning the vacuum depositions of SnO₂ and In₂O₃ films and the preparation of a conductive anti-reflection coating of 3-layers including its In₂O₃ film on a large sized glass plate.

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As the use of microphotographs has increased in modern microscopy, plan-apochromat objectives are indispensable that have well-corrected field curvature and no secondary spectrum over wide wave-length range. But, the correction of the field curvature and the elimination of secondary spectrum are apt to conflict each other, so designing the plan-apochromats is painful task. In this paper, the importance of adequate use of the materials with extraordinary partial dispersion is discussed using a simple thin-lens model.

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Dispersion of Selfoc lens originates from the wavelength dependence of the refractive index on axis N₀ and a constant A, where refractive index distribution is expressed as N=N₀ (1-A/2r²).
So far N₀ and A can not have been measured separately. Here, we proposed a new method of measuring A and N₀ separately.
First, A can be determined by making the parallel incident beam focus on the output end surface of Selfoc lens whose length is set up to a quarter of its periodic length.
Namely the length of Selfoc lens (Z₀) is measured under this condition, and A can be derived from the relation A= (π/2Z₀) ².
Secondly, we measured a distance (S) between the spot and the output end surface of Selfoc lens whose length (Z) is set up to shorter than a quarter of the periodic length. We found, then N₀ from N₀=1/S√A tan √AZ.
We measured A and N₀ for various wavelengths, and derived dispersion of A and N₀ separately.
We found the relation between A and λ (wavelength) such as, A= (A₂+B₂/λ²) / (A₁+B₁/λ²) R², where R is the radius of the Selfoc lens.

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It is pointed out that a damaged layer on the gadolinium molybdate single crystal which is produced during crystal cutting and polishing process, has a large effect on switching characteristics.
The relation between the depth of damaged layer and the switching characteristics has been investigated for several crystal fabrication processes. The result shows that the deeper damaged layer gives the higher switching threshold and the lower switching speed. The best switching characteristics can be obtained by using mechano-chemical polishing which can eliminate almost all the damaged layer. It is also found that conventional optical polishing technique can be applied for the fabrication of a quarter wave plate which does not require any switching characteristics.

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Developments of infrared lenses used at 3-14 μm are described. Germanium crystal is used as optical materials. Because the material's index is high and long wavelengths are used, it is possible to design nearly ideal lens. These lenses have small chromatic aberration, and therefore, can be used in infrared optical systems covering the wide band of wavelength with the combination of anti-reflection coatings and interference filters. Finally, the performances of manufactured lenses estimated with the modulation transfer function (MTF).

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Two sorts of contour mapping method using Moiré Topography are described.
The first method employs a plane optical grating that is placed in front of the test surface. The contour moiré pattern is produced by the reflected pattern from the test surface and the fixed standard grating. The reflected light is diffracted at the grating, and selected by the special filter so that the contour moiré is produced through an optical system onto an observation screen or can be directly viewed.
The second method is contour moiré method using a curved optical grating such as the surface of a test object. A contour moiré pattern is produced within a space between the surface of grating and the test surface.
These methods are simple but precise enough for testing the surfaces of optical parts in the course of manufacturing. The sensitivity of contour moiré methods can be chosen between 0.003mm and 0.1 mm.

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