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X-Ray emission at 4-5 keV from Xe Atoms with Multiple Core Vacan- cies,'' Nature 370, 631 (1994). A. B. Borisov, A. V. Borovskiy, V. V. Korobkin, A. M. Prokhorov, 0. B. Shiryaev, X. M. Shi, T. S. Luk, A. McPherson, J. C. Solem, K. Boyer, C. K. Rhodes, "Observation of Rela- tivistic and Charge-Displacement Self-channeling of Intense Subpico- second Ultraviolet (248 nm) Radiation in Plasmas," Phys. Rev. Lett. 68, 2309 (1992). A. B. Borisov, X. Shi, V. B. Karpov, V. V. Korobkin, J. C. Solem, 0. B. Shiryaev, A. McPherson, K. Boyer, C. K. Rhodes, "Stable Self-Chan- neling of Intense Ultraviolet Pulses in Underdense Plasma Producing Channels Exceeding 100 Rayleigh Lengths," JOSA B 11, 1941 (1994).

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WR 1530-1 700 Room 301 B

Optoelectronics Technology in Consumer Electronics II- Information Equipment II

T. Murakami, Toshiba R 6 D Center, Japan, Presider

WR1 (Invited) 1530

High-density optical disk using two dimensional recording

Takeshi Maeda, Central Research Laboratory, Hitachi Ltd., 1-280, Higashikoigakubo Kokubunji-shi, Tokyo 185, Japan To make higher density on optical disk, a new recording method-two dimen- sional recording- which can increase the tract-density rather than the linear den- sity was proposed. The performance of this method on increasing density is es- timated by the simulation and confirmed by measuring the read-out signal. Con- sequently, it is clarified that this method can attain more than twice the areal den- sity independently and realize the den- sity of 2.2 Gbit/squared-inch which is 8 times as large as that of first generation using 680 nm laser diode.

WR2 (Invited) 1600

Sony dynamic digital sound

Etsuro Saito, Kiyoshi Osato,* rakashi Nakao,' Broadcast Products Company, Mechatronics Development Department, Sony Corporation, 4-24-2 Asahi-cho, Atsugi-shi, Kanagawa-ken, 243 Japan Motion pictures conventionally are a sound playback system based on analog optical storage methods. Recently, there is an increasing demand for a high qual- ity digital sound system, so we have de- veloped a simple and high quality optical digital sound system called SDDS. For the conventional system, sound is re- corded by modulating the film optical density or transparent area in an analog manner. On the other hand, SDDS uses

optical digital storage method and infor- mation is recorded using a dot pattern.

To retain the conventional analog soundtrack and enough area for the dig- ital sound storage, we use the area be- tween the perforation holes and film edge. (Figure 1)

The size of the dots were determined considering following requirements.

1. 8-channel digital sound data rate of 1.2 Mbps.

2. 39% redundancy to obtain a strong error correction.

3. Adequate dot size to achieve the reliable contact printing. The horizontal pattern has 69 dots including a horizontal sync and data pattern. Also each horizontal track has guard band to ensure adequate track separation.

The recording system has 69 Light Emitted diodes placed in a line. Using this system, the horizontal dot pattern is recorded track by track on the master negative film. From this master negative, large number of copies can be pro- duced using the conventional contact print method.

The optical reader unit is placed between the supply reel and the picture projector. (Figure 2) Data areas on both edges of the film are illu- minated by Light Emitted Diodes which pro- vides a simple and durable illumination source. (Figure 3)

The Light Emitted Diodes on pulses are syn- chronized with the horizontal track pattern at 17.2 kHz. The guard band of each horizontal track prevents the cross-talk from neighboring tracks.

The film exhibits some unwanted sideways movement. To compensate for this variation, the scan timing for the linear image sensor is ob- tained from the horizontal sync pattern.

Any damage of up to 1.27 mm in length along the track and 336 km in the horizontal direction can be corrected with the error correc-

digital sound digital sound

1 i

t analql Swnd

&Mots c

ligh

linear image m r

WR2 Fig. 3. Principle of optical readout system.

tion code. The useful life of the SDDS sound track is at least the same as the picture itself.

In SDDS, two digital soundtracks are re- corded and both tracks contain mutual support data. These corresponding data patterns are re- corded 17.8 picture frame apart. So even in the event of severe damage such as the loss of part of a digital soundtrack, the digital sound is re- covered from another supporting soundtrack. This is called a digital back-up. Finally, if the digital back-up does not work, playback will switch over to the analog soundtrack.

We have developed a digital movie sound system called SDDS. It delivers more channels, better audio quality and higher reliability than ever before. *Opto-Electronics Research Department, Research Center, Sony Corporation, 6-7-35 Kitashinagawa, Shinagawa-ku, Tokyo, 141 Japan

WR3 (Invited) 1630

Development of variable bit rate disc system

Kentaro Yokouchi, Kenji Sugiyama, Mitsuaki Fujiwara, Kohji Tanaka, Shigeru Nemoto, Kazumi Iwata, Technology Development Division, Victor Company of Japan, Ltd. (JVC), 58-7, Shinmei-cho Yokosuka, Kanagawa, 239, Japan Recording motion picture on a CD-size disc with a density more than 4 times that of CD using MPEG2 has been at- tempted. However, recording a movie of more than 2 hours on the single disc without losing picture quality, was diffi- cult. Authors challenged this problem with a variable bit rate coding system. For encoding, the code amount is changed responsive to the variation of pictures without losing the picture quality.

Specifications of the developed pro- WR2 Fig. 1. SDDS track placement as seen from emulsion side of film.

totype are shown in Table I. Red lasir is employed for reading, having a total ca- pacity of 3 GB, the disc has a same di-

""tiOnal

1 WR2 Table 1. Suecifications of the

-D

d

WR2 Fig. 2. Playback system.

8 channel

Disc System

Diameter: 120" Thickness 1.2"

Single Sided Disk size

Optical Condition Track Pitch 0.79 pm Minimum Mark Length 0.47 pm Modulation Modified EFM Data Transfer Rate Total Capacity

A = 680 nm, NA = 0.6

Approx. 8 M bps Approx. 3 G bytes