Takashi Shionoya

Laser Scanning Mode Interference Contrast Microscope and Its Application to Step Height Measurement

The image contrast of the laser scanning mode interference contrast (LASMIC) microscope is descrihed. Some experimental results show the high performance of the LASMIC microscope in visualizing small phase changes on the surface of the sample. Furthermore, as a new application of the LASMIC microscope, quantitative measurement of step heights using LASMIC signals is proposed. The principle of this measurement is described theoretically and its effectiveness is verified experimentally.

High-resolution displacement measurement using mode interference in the optical waveguide

Using an optical waveguide, high-resolution displacement measurement is achieved for the first time. The measurement principle is based on the interference between the two (even and odd) modes in the double-mode waveguide. After the light from a laser diode is focused onto the object to be measured, the wavefront gradient of the reflected light is detected using a Ti-indiffused LiNbO/sub 3/ channel waveguide. Although this optical measurement system is very simple, very high resolution (of less than 1 mn) is obtained. Besides, the characteristics of the measurement system do not depend on the surface condition of the object.

Characteristics of a high-resolution displacement sensor using mode interference in the optical waveguide

A high-resolution optical displacement sensing system using an optical waveguide is fabricated and characterized. The measurement principle is based on interference between an even and odd modes in the double-mode waveguide. After the light from a laser light source is focused onto the object to be measured, a wavefront gradient in the converged reflected light beam from the object gives a phase asymmetry at the entrance of the double-mode (DM) waveguide. A change of the phase asymmetry due to the displacement of the object along the optical axis is detected as a change of light intensity distribution at the exit of the DM waveguide. Although the optical system is very simple, experimental results using Ti-indiffused LiNbO3 waveguide device shows a very high resolution less than 1 nm. Next, a compact-type displacement sensor module using silica waveguide is fabricated and shows an identical high resolution. In conclusion, it will be very useful as a built-in component for various kinds of the industrial equipment.

Light Scattering Studies on the Intermediate Phase Near the α-β Transition of Quartz

Raman and Brillouin spectra were simultaneously measured near the α-β phase transition temperature Tc (573°C). Three temperature dependent modes have been observed between Tc and Tc+2.0 K. They are; (a) a mode near 7 cm-1 observed in Raman spectra, (b) a quasi-elastic broad mode extending between Rayleigh and LA mode at 0.8 cm-1 and (c) an elastic component whose intensity being maximum at Tc+1.2 K. Intensities of these three modes are significant only in a small temperature range above Tc which is approximately equal to that of the incommensurate phase reported by Gouhara et al. using X-ray topographs. The peak frequency of the first mode decreases toward Tc+2 K, suggesting that the mode might be a soft mode related to the incommensurate phase transition. Possible origins of the other modes are also briefly discussed.

Characteristics of a Guided-Wave Displacement Sensor Based on Wavefront Detection

The characteristics of a guided-wave displacement sensor based on the wavefront detection are obtained. The displacement is measured by detecting the wavefront gradient of the light reflected from the measured object. The wavefront gradient is determined using the mode interference of the even and odd modes in the double-mode waveguide which is fabricated of silica glass on a Si substrate. The measuring range is 3 µm and the resolution is determined to be less than 1 nm. The object tilting dependence and the stability of the sensor are also measured. Furthermore, sample surfaces are observed and very fine images are obtained using this sensor. The optical system is very simple and the sensor is very compact, hence it will be useful as a built-in component for various kinds of industrial equipment.