Development of optical pickup for mini disc drives

In order to miniaturize optical disc drives, it is important to miniaturize and thin the optical pickup. We have developed two new optical parts: the hologram laser and the actuator. By optimizing the hologram pattern of the hologram laser, optical path length is shortened. The frequency characteristics of the actuator have been stabilized by improving the damping characteristics. Thus, we have developed a compact optical pickup for Mini Disc drives, and the pickup shows high performance when it reads out an optical disc.     

X-ray analysis of supercooled water

X-ray diffraction patterns of supercooled water were obtained at -5 and -10°C. Pretreated X-ray film was used for the measurements. X-ray intensity was measured by counting the density of developed Ag grains under a microscope. The radial distribution functions were derived from the intensity curves.     

Estimating function with asymptotic bias and its estimator

We introduce the estimating function with asymptotic bias and investigate the asymptotic behavior of the estimator based on it by using their relationship. The estimator based on the estimating function with asymptotic bias has the asymptotic normality with asymptotic bias. We show that this theory has several interesting applications in practical statistics.     

Simplification of Space-Variant Parallel Logic Operations Using the Temporal Method

A time-domain encoding method (temporal method) for space-variant parallel logic operations, which can execute different operations in parallel, is proposed. The temporal method is based on temporal encoding of two input patterns, temporal gating of the coded pattern, and decoding by temporal addition of the gated patterns. The first feature of the proposed method is that parallel logic operations can be performed without complex pattern transformations. The second feature is that the logical output can be directly fed to succeeding systems without specific decoding. Therefore, the logic operation system can be constructed using conventional optics and existing spatial light modulators. In order to confirm these features, an optoelectronic experimental system is constructed and space-variant parallel logic operations are performed.     

High Sensitive Detection of Trace Gases Using Optical Heterodyne Method with a High Finesse Intra-Cavity Resonator

A novel highly sensitive method to detect the concentration of trace gas for environmental purposes is proposed. This method includes the application of frequency modulation for stabilization of laser frequency, together with optical heterodyne measurement. The shift of resonance frequency of the Fabry-Perot cavity resonator is due to the change of refractive index, accompanied by the dispersion effect due to the presence of a target gas (e.g., methane, carbon dioxide or nitrogen dioxide) inside the Fabry-Perot cavity.     

Feasibility study of low-power multiquantum-well vertical transmission optical amplifiers for optical interconnection

Performance of 0.98-μm InGaAs strained multiquantum-well Fabry-Perot vertical transmission optical amplifiers (MQW FP VTOAs) for optical inter-board connection is analyzed theoretically, and compared with those of GaAs MQW, GaAs bulk, and InGaAsP bulk VTOAs. A low-power operation of about 2 mA and a cascadability of several hundred boards are predicted for an InGaAs strained MQW FP VTOA.     

Adsorption behavior of various metals on a weakly basic anion-exchange resin in sulfuric acid media

A systematic study is presented on the adsorption behavior of some 20 metals on a weakly basic condensed phenol resin, Amberlite CG-4B, in sulfuric acid media. The distribution coefficients were determined over a sulfuric acid concentration range of 0.005 M to 2 M. The metals adsorbed are similar to those which exhibit strong adsorption on a strongly basic resin, but the magnitudes of the distribution coefficients and the adsorption sequences differ considerably between the two types of the resin. Several two- and three-component separations of analytical interest are possible. A new method for the separation of titanium(IV) is described; this is based on its high adsorption on CG-4B from sulfuric acid media containing hydrogen peroxide.