| 摘要 |
PROBLEM TO BE SOLVED: To provide the optical unit which can detect a focusing state by using a small number of photodetection areas and make the optical pickup device small-sized and easy to assemble, and the optical pickup device using it. SOLUTION: The optical unit has a semiconductor laser 2 arranged on a semiconductor substrate 1, a tripartite optical detector 3 which is formed on the semiconductor substrate 1 and has three photodetection areas divided with two division lines, a going and return optical path separating means 4d which projecting the laser beam from the semiconductor laser 2 on the side of a recording medium 6 through an objective 5 and guides the return light from the recording medium 6 to the side of the tripartite optical detector 3, and luminous flux splitting means 4c and 9 which obtain pieces of luminous flux by dividing the section of the return light made incident on the tripartite optical detector 3; and the pieces of luminous flux split by the luminous flux splitting means are made incident on the photodetection areas on both the sides including one division line of the tripartite optical detector 3 and both the photodetection areas including the other division line to detect a focus state. |
