| 摘要 |
PURPOSE:To attain accurate detection of out-of-focus stably and to attain ease of correction of out-of-focus by providing a photodetection member provided at right angles to a direction where focusing spots formed at focusing are arranged to a photodetector and irradiating light used for the detection of out-of-focus. CONSTITUTION:Since the photodetector 37 is placed at a focusing plane in the detecting direction at focusing or its vicinity, read laser light 5 and recording laser light 4 are separated geometrically on the photodetector 37, the read laser light 5 is irradiated on a photodetection cell (photosensing region) 39, the recording laser light 4 is irradiated on a light unsensing region 40, and a preceding beam 6 is irradiated on the photodetection cell (photosensing region) 41. In arranging the photodetection cells 39E, 39F at right angles to the direction where the read collecting beam spot 8, the recording collection beam spot 7 and the preceding collection beam spot 9 are arranged, the area of the two photodetection cells 39E, 39F is equal and even if the focus is brought into out-of-focus in any direction, the out-of-focus detection signal is obtained nearly equally. |
