Recently in the high density optical disk system, a low noise laser and a precise power control method are required. This paper describes a fast laser power control method for the optical disk system. As a result, we achieved a lower noise level about -125dB/Hz using wide band laser power control. This method has been achived high control band with over 20MHz, using phase-lead compensator, and suppress the fluctuation of the laser power resulting from optical feedback.
A magneto-resistive(MR)/Inductive integrated head for high density magnetic recording was developed. The MR element is fabricated as a laminated permalloy layer of vertical type, whose structure reduces the Barkhausen noise. And to improve the reliability of the head, the head surface, which is exposed to the air, is set to the ground level. As the result, the electro-discharge causes no damage on the MR element. It is indicated that the output level of the vertical type MR is independent of the track width, and its offtrack characteristic is excellent. Therefore this type of MR head has capability of over 5000TPI track density.
LOT codec for Hi-Vision Digital VTRs has been developed. The codec compresses the Hi-Vision signals by the intrafield 2-dimensional LOT (Lapped Orthogonal Transform) and the mutilple pairs of the scaler quantizer and the VLC generator. The data rate per field is kept constant by the new data rate control algorithm minimizing the objective function considering the picure quality and the constraints on the target data rate. The results of the experiments by the computer simulations and the subjective assessment tests are described by comparing with the DCT codec using the proposed data rate control.
This paper describes comparison of error correcting schemes for optical memory card(OMC) systems. Two OMC systems are proposed as an ISO standard. One uses Reed-Solomon codes for error correction, the other uses (272,190) code. Results of computer simulation, it is unveiled the (272,190) code is more powerful than the Reed-Solomon codes.