Hitoshi Yanagisawa

Feed-forward tracking servo system for high-data-rate optical recording

A high-speed and highly precise track-following control system for high-data-rate optical recording is proposed. We are developing an optical disk camera-recorder to record high-definition television signals for collecting broadcast program materials. This system must have both a high data transfer rate of more than 100 Mbps and a large recording capacity. That requires high-speed rotation of the optical disk and highly-precise optical head control for tracking on narrow-pitch disks. To meet these requirements, we propose a new tracking control method consisting of a feedback controller and a feed-forward controller that employs the zero phase error tracking method. Simulation results show that the feed-forward controller suppresses tracking error. Suppression of tracking error is also shown by experiments using an optical disk tester composed of a blue-violet laser and a high-density optical disk controlled by an experimental device that implements the optimized algorithm of this control method at high speed.

High-Speed Tracking Method Using Zero Phase Error Tracking-Feed-Forward (ZPET-FF) Control for High-Data-Transfer-Rate Optical Disk Drives

We describe the effectiveness of feed-forward control using the zero phase error tracking method (ZPET-FF control) of the tracking servo for high-data-transfer-rate optical disk drives, as we are developing an optical disk system to replace the conventional professional videotape recorder for recording high-definition television signals for news gathering or producing broadcast contents. The optical disk system requires a high-data-transfer-rate of more than 200 Mbps and large recording capacity. Therefore, fast and precise track-following control is indispensable. Here, we compare the characteristics of ZPET-FF control with those of conventional feedback control or repetitive control. Experimental results show that ZPET-FF control is more precise than feedback control, and the residual tracking error level is achieved with a tolerance of 10 nm at a linear velocity of 26 m/s in the experimental setup using a blue-violet laser optical head and high-density media. The feasibility of achieving precise ZPET-FF control at 15000 rpm is also presented.

Method of shot determination in a robot camera cooperative shooting system

We are building a program-production system employing multiple robot cameras as a new program-production support technology. In this system, the robot cameras are automatically controlled in accordance with shooting rules that specify the relationship between changes in the program situation and the shots taken by individual cameras, but studio layout elements, such as the number of participants and the position in which flip-cards are displayed, are different for each program. For this reason, production staff must reset shooting rules for every program, and this operation is extremely burdensome in the limited preparation time available. We therefore devised a method of automatically generating shooting rules through simple information input based on analysis of the shooting methods of cameramen, and have tested the validity of this method in simulation tests. Moreover, we built a program-production system in which robot cameras are connected via a network to various sensors that we developed to detect changes in the program situation, and we evaluated the system by conducting program shooting experiments whose subject is engaged in actual TV program production.

Blue-Violet Two-Beam Optical Head for High-Speed Recording

We proposed an optical head using two laser diodes, which can control each plane of polarization of the two beams from the laser diode individually. The optical head makes it possible to decrease crosstalk light markedly by spatially isolating two beams during playback. An optical disk apparatus employing the optical head was constructed and the two optical spots were aligned on an optical disk at an interval of approximately 10 µm. Writing and reading in parallel were performed using the two blue-violet beams. We obtained a crosstalk intensity of -48 dB against carrier intensity and demonstrated operation at a bit rate of 200 Mbps.