| 摘要 |
PURPOSE:To make an optical system small through the constitution of minimum elements by installing a holographic element to divide a reflected light from a recording medium into two in an optical path between a light source and the recording medium. CONSTITUTION:The emitted light of a semiconductor laser 201 is converged on the recording medium 204, and its reflected light is made incident on the holographic element 205 of an unequal pitch grating such that a grating interval comes gradually narrow as it approaches to a periphery, and the flux of light is divided into two by the generation of an astigmatism, and the two are detected by deflecting plates 206, 207, and a servo signal and a magneto-optical signal are obtained by photodiodes 208, 209. Accordingly, the element 205 is placed in the midway of the light source and the recording medium, and a light emitting part and a light receiving part are made to draw near each other, and a beam splitter or a convex lens are omitted, and the optical system can be made small by constituting it of minimum elements. |
