| 摘要 |
PURPOSE:To obtain a miniaturized and light optical head by arranging a hologram element between an objective lens which converges light from plural light sources with different wavelength on a recording medium and the light source, and introducing the light diffracted by the hologram element to a photodetector. CONSTITUTION:Semiconductor lasers 1a and 1b with different wavelength are arranged adjacently, and the emission light of them are made incident on a transmission type diffraction grating 2, and 0th-order light transmitting the diffraction grating are converged on a magnetic film that is the recording medium 5 formed on a disk substrate 4 by the objective lens as spots 6a and 6b, respectively. And information on the recording medium 5 can be erased by lighting the laser 1b and changing the direction of the magnetic field of a thin film magnetic head 7, and also, new information can be recorded. Meanwhile, the spot 6a by the laser 1a is used for the readout of the information. The light reflected on the recording medium 5 is made incident on the diffraction grating 2, and 1st-order diffracted light is introduced to photodiodes 8a and 8b, then, is used in the detection of a focusing error signal, etc. |
