| 摘要 |
PURPOSE:To reduce crosstalk without complicating the constitution by forming an incident aperture nearly to a rhombic shape, and making a diagonal line orthogonal to a track of an information recording medium. CONSTITUTION:The aperture 7 arranged to the side of the light source 1 of an objective lens 4 is formed to be rhombic, the aperture 7 is formed nearly to be a square and a diagonal line is arranged so as to be orthogonal to a track direction A of an optical disk 2. A laser beam radiated from the light source 1 passes through a diffractive grating 5, a beam split prism 6, then the cross sectional shape of the beam is regulated by the aperture 7 and made incident in the objective lens 4, and a spot is focused on an information recording face of the disk 2. Then the reflected beam from the information recording face 3 of the spot passes through the objective lens 4 and the aperture 7, separated by the beam split prism 6, received by a photodetector 7 through a cylindrical lens 9 to read the information. Thus, crosstalk is eliminated. |
