| 摘要 |
PURPOSE:To reduce the effect of the thickness of substrate of a photodetecting element by shaping an edge into wedge shape which functions as a knife edge of a track detecting photodetecting element which masks a part of a reflected luminous flux given from an optical information recording medium and detects a focal point. CONSTITUTION:For a photodetecting element 8, a photodetecting surface 12 is formed on a substrate 11 and the substrate 11 has about 1-2mm. thickness. As a result, a part of the reflected luminous flux fed from a disk is masked by the edge face of the element 8. When the remaining luminous flux is made incident on a focus detecting photodetecting element 9, the luminous flux is partially reflected by the end face of the element 8 and turned into the flare light 13. Then a part of the luminous flux to be received by a focus detecting photodetecting element B is received by a photodetecting element A. Here an edge functioning as a knife edge of the element 8 is formed into a wedge shape. At the same time, the end face of the substrate 11 is painted in black or changed into a coarse surface. Thus it is possible to reduce the light 13 and prevents the drop of the detection signal level. |
