| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical head which is small in size and is capable of reducing the number of input-output terminals by substituting the photodetector of a CD(compact disk) optical system for the monitor of the output of a used laser without using an exclusive photodetector at the time of a high density recording. SOLUTION: In the case of recording/reproducing an information signal with respect to a DVD-RAM, the light beam with a wavelength of 650 nm emitted from a first semiconductor laser 1 passes through a polarizing beam splitter 3 to be made incident on a wave selection prism 14 and 95% of the beam transmits the prism and the remaing 5% of the beam is reflected in the direction of 90 deg.. The reflected light beam is guided to an optical module 2 to be made incident on the light receiving surface of an internal photodetector and it is converted into an electric signal in accordance with a light quantity. In the case of recording an information signal with respect to the DVD-RAM, since the light beam is controlled so that the photodetector is operatable, the detector can be used as a power monitor. |
