This study aims at achieving a high speed optical disk drive for multimedia storage used in network systems. The feasibility of our target has been confirmed by the following results and techniques. High speed parallel data transfer at 336 Mbit/s in 2/7 run length limited (RLL) code or 300 Mbit/s in 1/7 RLL code has been achieved experimentally with eight beams. Focus offset has been reduced by a multibeam laser diode fabricated in junction down structure and a wide-angle lens system. Tracking error is reduced by nearly 6 dB compared with that of a conventional method. This was achieved by suppressing the mechanical interaction between the lens actuator and the beam rotation prism. The crosstalk canceler reduces both intercircuit crosstalk and optical crosstalk with pseudo crosstalk generated by a circuit. It reduces the worst-case intercircuit crosstalk by more than 14 dB.

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The theoretical basis for a write-compensation scheme is developed with a simplified thermal transfer function in an optical disk. The thermal transfer function is analytically approximated to a first-order exponential filter similar to that of an integrating circuit. A write-compensation method is then given directly by the inverse function of the filter. A simplified form of the compensation is also derived, and this is verified by experiments. This method eliminates the thermal interference and shows how to form mark edges uniformly for an arbitrary optical disk.

A new, simplified readout waveform equation for an elliptical mark is analytically derived and confirmed. This approach easily treats an effiptical mark by using an equivalent rectangular mark having 6 function width and equivalent readout beam spot. The equation is verified by comparison with precise numerical calculations. Good agreement is obtained for practical dimensions of optical recording. The equation gives the characteristics of the readout waveform directly from the elliptical mark.