| 摘要 |
PURPOSE:To provide a low-cost optical information recording and playback apparatus wherein the relative movement speed between an optical recording medium and an optical head can be constituted without a need for a special prerecorded pattern in each track and without being affected by a dust particle and a defect on the surface of a card. CONSTITUTION:The following are arranged respectively: a first photodetector 71, for information playback use, and a second photodetector 81, for information playback use, which photodetect beams of reflected light from two light spots formed in a track on an optical card by means of an optical beam for information playback use. A counting operation is started on the basis of the output of a pit detection by means of the first preceding photodetector 71 for information playback use; a speed data detection means is installed by using a counter group 79 which sequentially measures the time up to a pit detection by means of the second posterior photodetector 81 for information playback use. |
