| 摘要 |
PURPOSE:To reproduce faithfully, and to eliminate noise of a signal to decrease a wrong read at reproducing by constituting a photodetecting area of a photodetecting means, so that at least a part of the part excluding the peripheral part of a luminous flux is photodetected. CONSTITUTION:A laser luminous flux L which has been reflected from an information storage medium 22 is irradiated onto a photodetector 30 and a photodetector 31 by passing through a half prism 28, and being reflected, respectively. As for this detector 31, a size of its photodetecting area 31a is set so as to become smaller than a size by which an optical intensity of the projected luminous flux L becomes 1/e<2> against the center intensity, and at least a part of the part excluding the peripheral part of the luminous flux L is photodetected. In this way, information which has been stored in the medium 22 is reproduced faithfully, noise of a jitter, etc. of a signal is eliminated, and wrong read at reproducing the information can be decreased.
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