Kazuo Takashima

Optical inspection system for the inner surface of a pipe using detection of circular images projected by a laser source

Abstract An optical inspection system for the inner wall of a pipe has been developed. This system uses the projection of a circular pattern formed by a conically reflecting mirror on the inner wall, and detection of circular images from the illuminated circumferential surface. Irregularities of the images due to corrosion or accumulation of deposits on the inner surface are inspected by this system. Inspection of the shape of the inner wall has been impossible by current methods. The experimental system reported in this paper has the following practical specifications: resolution of detection on ±0.1 mm, and inspection speed of 30 mm/s at an interval of 1 mm along the pipe. The system is now being used for practical inspection.

Magnetooptical properties of diluted magnetic semiconductor CdMnCoTe films

The relationship between Faraday rotation /spl theta//sub F/ and magnetic field H in the visible wavelength region for films of the diluted magnetic semiconductor CdMnCoTe deposited on quartz glass substrates by molecular beam epitaxy is examined. The magnitude of /spl theta//sub F/ in the CdMnCoTe films is compared with that in CdMnTe film and ferrimagnetic garnet Bi:YIG film, and it is shown that the Faraday rotation for Cd/sub 0.51/Mn/sub 0.414/Co/sub 0.076/Te film is approximately three times that for Cd/sub 0.39/Mn/sub 0.61/Te film. The value of /spl theta//sub F/ in the Cd/sub 0.51/Mn/sub 0.414/Co/sub 0.076/Te film at an optical wavelength of 670 nm was -0.2/spl deg///spl mu/m under a magnetic field of 6.8 kOe. The relationship between the values of /spl theta//sub F/ for the diluted magnetic semiconductor films and the substrate materials is also discussed.

Micro-optical distance sensor fabricated by the LIGA process

An ultra-miniaturized sensor head for absolute measurement which has a size of less than 5 mm cube is realized. The sensor works by means of the optical triangulation. To achieve the optical function, the sensor consists of a three layer polymer waveguide patterned by X-ray lithography, an incoupling fiber and two detection fibers and micro cylindrical lenses which are also fabricated by X-ray lithography. The fibers and the cylindrical lenses are placed into the waveguide without any active alignment by using waveguide walls as guiding and fixing structures. The ratio of intensity detected in the two detection fibers is a measure for the distance between the object and the sensor. The detection range of the sensor is 1 to 6 mm between the sensor and an object with diffusively reflecting surface.

Evaluation of Faraday-rotation characteristics with CdMnCoTe and CdMnFeTe films

Magneto-optical properties with quaternary CdMnCoTe and CdMnFeTe films deposited on quartz glass substrates using molecular beam epitaxy equipment are studied at an optical wavelength of 635 nm. The magnitude of the Faraday rotation θF in the CdMnCoTe films was compared with that in the CdMnFeTe films, and the largest θF has been obtained for the Cd0.603Mn0.371Co0.026Te film. It is shown that a large θF was also observed in the Cd0.575Mn0.372Fe0.053Te film and its optical properties were poor compared to those in the Cd0.603Mn0.371Co0.026Te film. A few problems that occur for measurements of the Faraday rotation are indicated.Magneto-optical properties with quaternary CdMnCoTe and CdMnFeTe films deposited on quartz glass substrates using molecular beam epitaxy equipment are studied at an optical wavelength of 635 nm. The magnitude of the Faraday rotation θF in the CdMnCoTe films was compared with that in the CdMnFeTe films, and the largest θF has been obtained for the Cd0.603Mn0.371Co0.026Te film. It is shown that a large θF was also observed in the Cd0.575Mn0.372Fe0.053Te film and its optical properties were poor compared to those in the Cd0.603Mn0.371Co0.026Te film. A few problems that occur for measurements of the Faraday rotation are indicated.

Improvement of the spectral response in large CdTe detectors operating at low bias voltage

This paper reports a method to improve the energy resolution for /spl gamma/ rays of a CdTe semiconductor detector 15 /spl times/ 15 /spl times/ 15 mm/sup 3/ in size and with low applied voltage and an adequate electronic circuit constant. The principle of improvement is to make use of carrier trapping and ballistic defects. We investigated the improvement of the energy resolution by calculating the output waveforms using a Monte Carlo simulation. As a result, we could obtain an approximately 8% energy resolution of 662 keV equivalent to that of an NaI(Tl) scintillator. Further, the intrinsic efficiency of a full energy peak equivalent to that of a 1-in-thick cylindrical NaI(Tl) scintillator could be achieved. This method has the advantages that the energy spectra can be improved by simple systems and the noise is reduced because of the low leakage current due to the low applied voltage.

Fingerprint sensor using fiber optic faceplate

This paper presents a new fingerprint sensor for automated fingerprint identification systems. This fingerprint sensor consists of alight source, a charge coupled device and fiber optic faceplates. Because of the fiber optic faceplates, this fingerprint sensor does not have the space for image formation that a lens has and thus can be miniaturized. The size of the prototype fingerprint sensor, which has a 12 mm by 18 mm fingerprint input face, is 48 mm by 72 mm by 44 mm. The verification performance is evaluated by using this prototype.

Multi-electrode circular position-sensitive device (PSD) and its application to angular measurement

Semiconductor position sensitive devices (PSD) enable to measure the position of a light spot using simple construction. A circular PSD, which has a circular photosensitive region, can be used for angular measurement. This paper presents a new type of circular PSD called Multi Electrode Circular PSD (ME-CPSD) and demonstrates its application for angular measurement. This device, constructed on Si substrate, has a photosensitive region, a resistor line and 16 output electrodes. The photosensitive region has the shape of a ring which is formed by a radial arrangement of long and narrow photodiodes. The outer end of the photodiodes are connected to the continuous resistor line. Photoexcited carriers which are generated in the photodiode by the incident light flow to the resistor line and are extracted by the multioutput electrode which divides the resistor into 16 equal parts. To measure the position of the light spot, a pair of electrodes is selected by switches connected to every electrode and the position of the light spot is calculated from the output current of the selected electrodes. Compared to conventional circular PSDs, the reliability of the angular measurement is improved, because the ME-CPSD does not have an undetectable region caused by the unavoidable discontinuity in the structure of conventional circular PSDs. This device can change its measuring range by selecting the pair of electrodes, making it not only capable of measuring any absolute angular position, but allows also a more precise angular measurement by selecting narrower electrode intervals. This device has the capability to realize a high precision noncontact angular measurement system with simple construction.

Magneto-optical properties of DMS CdMnCoTe films

Summary form only given. Recently, a Faraday rotation in the four-element diluted magnetic semiconductor (DMS) CdMnCoTe films deposited on transparent SiO/sub 2/ quartz glass substrates by using molecular beam epitaxy (MBE) has been studied, and it has been shown that the Faraday rotation in those films was greatly enhanced. In this study, the magneto-optical properties of CdMnCoTe films are discussed from the viewpoint of application.