In this paper, we describe a stabilized three level recording method. which expands the readout resolution limit of conventional optical disk system. Specifically, the recording density of this three level method is achieved 1.4 times in the light intensity modulation using an exchange-coupled magnetic multi-layer film.
Playback signal level depends on shape correlation among effective aperture and recorded pit(s) on Magneto-optical Disks using Magnetic Modulation writing and Magnetic super Resotution Reading (MMW/ MSRR). To inspect this dependence, signal level difference between Normal Rotation Reading (NRR) and Reverse Rotation Reading (RRR) is compared.
Modulation noise in the reproducing process of a VTR may influence the error rate. We had already proposed a model of modulation noise which can be applied to sine wave recording. In this paper we study a mathematical model of modulation noise in reproduced digital signals. We analyzed the total noise by subtracting the ensemble mean from the reproduced signal. Based on this analysis, we confirmed that the formula for reproduced signal including modulation noise can be applied to digital signals. In addition, we found that modulation noise is dominant in the signal bandwidth.
This paper presents a strategy for reducing nonlinearities at high-recording densities; a new additional encoding scheme for DC-free d=1 channel codes, and a partial response (1+D) system with 2-bit decoding. This encoding scheme, which is applicable to DC-free codes, reduces by one bit the maximum transition interval of d=1 codes, and ensures a wide margin of timing offset. In order to use erasures for the error correction code, the 2-bit decoding scheme is employed in-parallel to detect errors in the decoding procedure. An improvement in the error rate by using parallel decoding is shown.
An HDTV digital video disk recorder which can record compressed HDTV signal and non-compressed 4ch audio signals for 32 minutes into a 30cm in diameter magneto-optical disk has been developed. This system is composed of HDTV codec and NTSC video disk recorder VF-200. The codec compress HDTV signal at 594Mbps to 94Mbps which is equal to effective NTSC data rate with intraframe DCT, Huffman coding and 2-stage bit rate control technique. The encoded data is recorded on the NTSC recorder VF-200 which is possible high density recording such as 1.6Gbits/In^2 and has the capacity of 23GBytes per disk.