This paper presents two types of novel focusing system for the use of zoom lenses.
And the study is made of their basic feature by use of the designed zoom lens.

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The expression for the third order aberrations of a meridional ray can be arranged into a simpler form which is composed of only two terms. These terms can be considered as new aberration coefficients, and also can be used effectively to determine the forms of lens elements. As an example, the application to a retrofocus lens system composed of four lens elements is illustrated.

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Two new techniques have been applied to the viewfinder of recent SLR camera“Minolta XD-s”. One of them is a new focusing screen named“Acute Mat”. The microscopic conical prisms of 20μm in diameter are distributed uniformly all over the screen surface. These microscopic prisms provide more brightness and clearness for observation through a finder, and also more easiness for focusing than the conventional screen. Another technique is the new eyepiece which provides the adjustable dioptric value for viewfinder. In the case of viewfinder equipped with a conventional eyepiece, the dioptric value of the finder is fixed to some standard value. However the viewfinder equipped with the new eyepiece gives adjustable dioptric value within the range from -2.7 D to+0.8 D. With this feature, a sharp finder-view has become available even to the people of slight myopia for presbyopia. This report outlines the principles of these new techniques.

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In the case of in-plane mounting, a stigmatic image condition for the whole wavelength region has been found, by means of the rotation of a toroidal grating and the slight movement of the both incident and exit slits, increasing with a rotation angle, ε, of the grating.

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Techniques and an apparatus for spectrophotometer using an acoustooptic tunable filter (AO filter) are described. Stray light of an AO filter, which disturbs the precise spectral measurement, is seperated from filtered light by the RF chopping technique. System control and data processing are performed efficiently with an one-chip CPU. Scanning time, spectral resolution, and wavelength region are 0.1 sec, 4nm, 400nm-700nm, respectively.

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The MRC-1 MTF TESTER in which charge coupled devices (CCD) are used as its photosensor was developed for production testing of facsimile lenses. Since a CCD is capable of selfscanning, the equipment does not require any large and precise mechanical scanning mechanisms giving MTF values for many field positions simultaneously. The MTFs at all 9 field positions for a single spatial frequency are given on the display panel. At the same time, green and red lights indicate whether a lens has passed or failed, having been compared with the acceptance level of MTF which was set by digital switches. The principle of the MRC-1 MTF TESTER is described and its features are discussed in this paper.

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The purpose of this instrument is rapid lens testing in the production line by MTF measurement. Linear self-scanned photo-diode arrays are used as scanners of the line spread function. A mini-computer is used for data processing and MTF calculation.

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The float glass process makes it possible to produce glass having perfectly flat surfaces, so that is rapidly replacing sheet glass process. This paper describes the float glass process, properties of float glass and some of the new application especially for optical industry.

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The grinding characteristics of optical glasses with respect to two kinds of diamond pellet (A-D.P and B-D.P) and investigated by comparing the experimental values of grinding hardness with those of volume loss. A-D.P and B-D.P, the products of two different companies, are different in their composition of bond, but they have equal diamond concentration and equal grain size. Sample glasses used are BK, SK, BaF, F, SF, LaK, LaF, and LaSF. As the result of investigation, a method to qualitatively represent the grinding characteristics with respect to D.P is proposed.
The relation between physical properties (the abrasion hardness with respect to loose grain, Knoop Hardness, and Young's modulus) and the grinding hardness is also examined.

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Dimming and staining resistivity of optical glass have generally been expressed in term of water durability (Dw), and acid durability (Da), which are determined by the powder method, in accordance with the specification of the Japanese Optical Glass Industrial Standards (JOGIS).
However, based on our experiences, the Da does not agree well with the staining resistivity for several glasses. Futhermore, Dw and Da do not represent the solubility of optical glass in water and detergent which is related to the generation of latent scratch with the hardness of the glass.
The rate of staining formation in water and the solubility of optical glasses in water, NaOH solution, and Na₅P₃O₁₀ solution which is a common corrosive inorganic-builder of detergent, have been studied.
The experimental method is as follows; polished glassed were immersed in H₂O controlled pH at 7, 1/100 M NaOH, 1/100 M Na₅P₃O₁₀at 50°C. After a given period of time of corrosion the weight loss of a glass was measured and interference color of the surface, which exhibits the optical thickness of the staining layer, was observed.
It has been found that,
1) In the case of the glass having poorer staining resistivity, Da exhibits lower value than that expected from the behavior of actual staining formation, because of the fault of the powder method. The staining resistivity should be measured directly.
2) Many newer type glasses easily generate latent scratch, in spite of having high chemical durability against H₂O and NaOH solution. It can been explained by reason that the glasses easily attacked by Na₅P₃O₁₀contained usually within detergent. The solubility of the glasses both in Na₅P₃O₁₀solution and in H₂O should be measured in order to know the resistivity of the latent scratch generation.

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The temperature coefficient of refractive index dn/dTand that of volume expansion β have been measured by an interferometric procedure designed to determine the coefficients simultaneously, with one sample. The temperature coefficient of electronic polarizability φ has been calculated from dn/dTand β. At first, φ is expressed as the sum of the contributions of each glass component, φ_i. Secondly, φ_i is expressed as follows: φ_i=β_i·γ_i, where β_iis the thermal expansion coefficient of cation-oxygen distance and γ_iis the change in electronic polarizability due to the change in interionic distance. φ_i decreases as the ionic field strength of cation, z/a² increases, which is the same tendency as that of β_i·γ_icalculated from φ_iand β_i, gradually increases as z/a² increases. This means that φ_iis mainly determined by the elongation of interionic distance, and it also suggests that the deformation of the electron cloud of oxygen ion caused by the change in interionic distance becomes larger, as the electronic polarizing power of cation increases.

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An apparatus for measuring spherical aberrations of photographic lenses is described. Instead of photographic plates, a solid state linear image sensor is successfully applied to give an increased accuracy, because it allows us to analyze the intensity distributions of the pinhole images. A drastic improvement is also obtained in the measuring efficiency by using an online computer directly connected with the image sensor. It is shown that some changes should be made in the measuring procedure in order to apply a solid state image sensor to Hartmann Test. Two standard lenses of known data are measured to test the apparatus. Then the limitations and the precision of the method are discussed in both theoretical and experimental manners.

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