Optical pickup device

反射镜14相对于物镜16倾斜并放置在一定位置，用于检测的光电转换元件15放置在反射镜14的背侧。反射镜14的结构中，具有预定反射率和透射率的半透膜HM形成在透明介质的衬底的一个表面上。当进行信息记录或信息再现的激光束从半导体激光器2a，3发射出并射向反射镜14时，半透膜HM将激光束分成反射光束和透射光束，反射光束射向物镜16一侧，而透射光束射向光电转换元件15一侧。结果，进行信息记录和信息再现的任何激光束可由光电转换元件15探测，以便进行半导体激光器2a，3的APC控制，针对信息记录介质进行信息记录和信息再现的激光束的光强可得到适当的控制。 A reflective mirror 14 is inclined and placed with respect to an objective lens 16 and a photoelectric conversion element 15 for monitor is placed in the back side of the reflective mirror 14. The reflective mirror 14 is formed into a structure in which a semi-transmission film HM having predetermined reflectance and transmittance is formed on one surface of a substrate of a transparent medium. When a laser beam for information record or information reproduction is launched from semiconductor lasers 2a, 3 to the reflective mirror 14, the semi-transmission film HM splits the laser beam into a reflected beam and a transmitted beam and the reflected beam is emitted to the side of the objective lens 16 and the transmitted beam is emitted to the side of the photoelectric conversion element 15. As a result of this, any laser beams for the information record and the information reproduction can be detected by one photoelectric conversion element 15 to perform APC control of the semiconductor lasers 2a, 3 and the intensity of the laser beam for the information record and the information reproduction with respect to an information record medium can be controlled properly.