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The read-write characteristics of an optical disk utilizing a blue-laser diode are examined, applying land and groove recording and partial response and maximum likelihood (PRML) to two optical disk systems: 1) 0.85 numerical aperture (NA) optical disk system consisting of an objective lens with NA of 0.85 and a thin cover layer on a disk with a thickness of 0.1 mm and 2) 0.65 NA optical disk system consisting of an objective lens with NA of 0.65 and a 0.6-mm-thick disk substrate. In the 0.85 NA optical disk system, the track pitch and the data bit length employed for the experiment are 0.29 µm and 0.0987 µm, respectively. These parameters correspond to a capacity of 30 GB/side. In the 0.65 NA optical disk system, they are 0.37 µm and 0.155 µm, respectively, corresponding to a capacity of 15 GB/side. A bottom channel bit error rate (ch.bER) of less than 5.0×10-5 can be obtained in these systems, and it is confirmed experimentally that the ch.bER remains below 1.0×10-4 up to 1000 cross-write cycles.

This paper presents a rewritable optical disk with a capacity of 30 GB/side intended for the next generation of rewritable optical disks. The experimental results have shown that this optical disk has wide tilt margin and is a prospective candidate for supplanting VCR in the HDTV era.

For the sake of establishment of a hydrogeological model, the relationships among geological, geophysical and hydraulic properties were discussed, by the use of the data obtained from the rock formation at the Tono area.Performances of hydraulic test equipments recently were also reviewed.Results are summarized as follows:(1) The hydraulic conductivities by PNC Aquifer Test Method (JFT) are quite similar with those by low pressure Lugeon Test Method.(2) Lithology such as grain size and sorting coefficent correlates with hydraulic conductivity.(3) Apparent resistivity, measured by electric logging (100cm normal), correlates closely with hydraulic conductivity.The high correlation between geological and geophygical properties and hydraulic conductivity make possible to estimate hydraulic conductivities by means of Ethology obtained by core logging and electric logging data. The hydrogeological model was successfully constructed by this method.

Nonlinear friction on a pickup head mechanism causes an objective lens shift. Detrack that causes the objective lens shift makes deteriorates read signal quality. To reduce the objective lens shift, we implement a nonlinear friction compensator in the pickup head. Experimental results confirm this compensator reduces the objective lens shift a quarter of not used.

The read-write characteristics of a land and groove disk have been examined using a blue-laser diode, high NA objective lens and the PRML method. The wide tilt and defocus margins have been obtained and no deterioration by CW has been observed at a data bit length of 0.0987 /spl mu/m and a track pitch of 0.29 /spl mu/m. These experimental results certify the feasibility of a rewritable optical disk with a capacity of 30 GB/side.

The possibility of an optical disk capacity of 28GB/side is studied. The read-write characteristics of a phase-change optical disk are examined using a thin cover layer, a blue laser diode, high NA objective lens and the PRML method. The wide tilt margins of high-density recording are achieved.

High speed accessing is necessary for optical disk drives, which are used as computer peripheral equipments. A direct track seeking technique was introduced and a new light weight moving part was designed to make the track seeking time shorter. The average seeking time was reduced to 18 ms in an experimental optical disk drive, using an experimental 86 mm disk which was recorded in a sampled servo format.© (1990) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

In order to evaluate the phenomena of masstransportation by groundwater flow in granitic media, it is necessary to make clear geological, hydrogeological and geochemical characteristics of fracture distributed in rock mass.Characteristics of fracture pattern, fracture filling material and alteration in Upper Cretaceous granite are investigated by core logging, mineralogical study, geophysical logging and hydraulic testing. This report describes the results which were obtained in the interval from the ground surface to 500m at Tono area in the central part of Japan.The results are summarized as follows ;(1) Fractures are classified into four groups on the basis of fracture pattern; Planar group (P), Irregular group (I), Curved group (C), and Stepped group (S).(2) Most of fractures belonging to P group and S group have filling materials composed of chlorite, calcite and sericite. Some of the fractures belonging to I group have been filled with materials composed of montmollironite, sericite and chlorite. Fractures of C group hardly have filling material.(3) Some of alterated fracture zones are consisted of P group fractures.(4) As a result of analysis on the fracture pattern and alteration pattern, three segments are recognized; Segment I (from 16.8m to 300m), Segment II (from 300m to 420m), and Segment III (from 420m to 500m). Especially, there are marked differences in fracture pattern and alteration pattern between Segment I and Segment III.