| 摘要 |
PURPOSE:To miniaturize a device and to reduce the cost by making focus detection that uses tow photodetectors possible by single prism and integrating plural optical parts. CONSTITUTION:The prism 37 of a focus detecting device 30 is provided with the first and second semitransparent reflecting faces, and the single prism 37 is made to have the function of a beam splitter that separates a beam 45 for projecting an optical recording medium 16 from a beam 45 from the optical recording medium 16 and the function of a beam splitter that separates the beam 45 to detect the beam 45 from the optical recording medium 16 around the convergent point. A semiconductor laser 31, the prism 37 and the first and second light detector 33, 34 are integrated, and plural optical parts are arranged on the same plane of a semiconductor substrate 32. Thus, the number of parts is decreased, and the device can be miniaturized and low cost is obtd. |
