| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical reproducing unit capable of keeping reproduction power at a optimum value and reducing the probability of the occurrence of read errors without lowering the utilization factor of an optical recording medium. SOLUTION: A means for measuring a prescribed length mark signal is provided for measuring the amplitude values of a 2T mark and a 8T mark which are marks for each reproduction power control of two kinds of lengths from information data recorded on a magneto optical disk 1, respectively. The reproduction power of a light beam is controlled on the basis of each amplitude value of the 2T mark and the 8T mark. The means for measuring the prescribed length mark signal detects a specified pattern containing the 2T mark from the bit array pattern of information data, and measures a 2T mark amplitude value only corresponding to the 2T mark contained in the specified pattern.
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