A common-path interferometer with a modified zone plate for testing aspheric optical elements is given. The interferometer described here is the generalization of a conventional Fresnel zone plate interferometer developed by Smartt and is suited to test aspheric refracting elements as well as reflecting ones. Formulas to compute modified zone plates, especially for the conic sections of revolution, are presented. Error analysis for the setting of the zone plate is given and the inter ference pattern in the presence of three dimensional displacement of the zone plate is discussed. It is pointed out that one can set the zone plate by making use of the interferogram itself and thus test the performance of the elements easily. Some experimental examples are presented.

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It has been a very important problem till now in dentistry to investigate the deformation of teeth and mandibular bones subjected to occlusal or masticatory forces. Various measuring techniques have been utilized to measure their deformation on idealized models or patient's masticatory systems. In this paper holographic interferometry is given as a suitable solution of the problem. Holographic interferometry makes it possible to investigate three dimensional deformation of diffusely reflecting objects interferometrically. The principle of measurement and the measuring accuracy are described and an experiment is performed on the teeth and the mandibular bone of a dog. The lower first molar is subjected to lateral tensile forces from three different directions. The exposed regions of teeth and mandible are coated with white paint to increase the reflectance of the surface. This overcomes the difficulty in forming interferograms of biological materials. The resulting interferograms are evaluated to determine he displacements of the teeth and the surrounding structure. Experimental results are quantitatively discussed for each lateral tensile force.
When tensile force is subjected perpendicularly to lingual surface of the first retromolar, it is found that teeth and mandible deformed considerably to lingual direction.

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An optical heterodyne system with frequency-shifted and phase-modulated reference beam for Vibration phase measurement is proposed. Two different electrical filtering systems are considered: one detects the carrier frequency signal and the other detects the sideband frequency signal. In preliminary experiments to prove the validity of the theory, the vibration phase can be measured with the both filtering systems. Considerations show that the sideband detection system is superior to the carrier detection system, and this method is applicable to the vibration measurement of the rough surface.

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The wavelength control of diode lasers by a diffraction grating is studied with a view to applying the diode lasers to the wavelength-division-multiplexing-transmission. Experimental results show that (1) the only one wavelength is freely selected in a multi-mode diode laser, (2) the selected wavelength does not depend on the diode laser temperature, and (3) the oscillation wavelengths selected simultaneously from some diode lasers with a diffraction grating are controlled independently.

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