| 摘要 |
PURPOSE:To simultaneously read a signal recorded at a different mode with high reliability by arranging a 1/4 wavelength, a polarization beam splitter and a two- divided light detector at the light path of the reflecting light of a recording surface and subtracting, and adding an intensity difference signal. CONSTITUTION:On a disk 8 in which first information is recorded by a minute unevenness, second information is recorded in the shape of the change of magnetization to a magnetic optical medium 20 of a surface, the light of a laser 2 is made parallel by a lens, the straight line polarization is executed by a polarizer 4, and a part separated by a half-mirror 5 is lighted with the light converged by a lens 6. The reflecting light is returned through the lens 6 to a parallel light flux and the light intensity distribution at the far field is obtained. The half-mirror 5 is divided into an S polarization and a P polarization mutually orthogonal through a diameter 1/4 wavelength plate 9 with a polarization beam splitter 10 and passes through detectors 11 and 12 and differential amplifiers 13 and 14, respectively. The output of an adder circuit 15 of intensity difference signals 101 and 102 obtained is used for reading the first information, and the output of a subtracting circuit 16 is used as a signal for reading the second information. By such constitution, both pieces of information can be read with high resolution. |
