Tomio Yoshida

Optical Video Recorder Using Tellurium Sub-Oxide Thin Film Disk

A compact optical still video recorder using Te0x(x÷1) thin film disc and a laser diode as the light source has been developed for video signal recording and playback in a real time mode. The recorder is capable of storing up to 15,000 still pictures on one side of a pregrooved disc, 200 mm in diameter with an average random access time of 0.5 seconds for any desired frame. The reflectivity of TeOx thin film recording layer which is deposited on a pregrooved plastic substrate by evaporating Te and TeO2 compound varies with absorption of irradiated thermal energy of focused laser beam. Carrier to noise ratio greater than 55 dB were achieved at incident power level of 7-9 mW, which was focused by an objective lens having numerical aperture (N.A.) of 0.5. Signal to noise ratio of more than 43 dB and resolution of more than 260 TV lines of playback video signal were obtained.

Compatability test for phase-change erasable and WORM media in a multifunction drive

We have presented configuration of the multifunction drive, interchangeability test, and reliability test consisting of temperature test and reading many cycles test. The multifunction drive could be realized by adding laser power control block and the polarity switch of reading amplifier without changing the WORMs head on a current WORM drive. Interchangeability test results showed having good interchangeability among multifunction drives or among WORM drives, and also the multifunction drive had full compatibility with current WORM drive on the current WORM disk. Reliability test results for the multifunction drive using a PCE disk and a WORM disk showed that writing sensitivities of both disks were much less dependent ont he temperature and the drive had stable writing characteristics in environments from 5 degree(s)C to 50 degree(s)C, and furthermore no error bit was observed while reading the most inner track of each disk 10 million cycles with the read power of 1.8 mW being 20% up to normal one at 6.1 m/s of disk velocity.

Performances of pregrooved phase-change rewritable media in the 680-nm laser diode system

The performances of the pregrooved Phase Change Rewritable (PCR) media have been measured by using an test drive which optical head have a 680 nm laser diode and focus lens with numerical aperture of 0.55. The write/read characteristics and groove parameters have been measured. The linear density of 1.42 Kbits/mm by using Pulse Position (PPM) recording method and track pitch of less than 1 micrometers are expected to be realized.