| 摘要 |
PURPOSE:To provide an optical information recording and playback apparatus wherein, even when a large irregularity in a pit on a recording medium is caused due to a change or the like in a light-emitting quantity, the center of the pit can be detected accurately and a piece of data can be played back accurately. CONSTITUTION:The following are installed: a light spot formation means for playback use which is constituted by using a semiconductor laser 40, a diffraction grating 44 and the like which forms two light spots for playback use on one track; a photodetector 17 which is provided with a first photodetector for playback use and a second photodetector for playback use which photodetect said respective light spots for playback use; and a pit-width detection means which detects the front end and the rear end of a pit formed on an optical card 7 from the output of said first photodetector for playback use. A pit central-position judgement means which detects the central position of the pit on the basis of the output of said second photodetector for playback use corresponding to the pit and on the basis of the output of the pit-width detection means. |
