| 摘要 |
PURPOSE:To contrive miniaturization with lighter weight and high speed access capability of the subject device by emitting zeroth-order light and 1st-order light under the state of their separation angle of 0 by 1st and 2nd diffraction gratings, detecting them with 2- and 4-divided photodetectors and obtaining a magneto-optical signal from their output difference. CONSTITUTION:Reflected light from a disk is incident upon the double diffraction gratings 16 via a splitter 5. Transmitting light from the 1st diffraction grating 17 is passed straightly through the 2nd diffraction grating 18 while diffracted light is diffracted by the grating 18 to become convergent light having astigmatism. Then, transmitting light 21 and diffracted light 19 by the grating 16 are turned into concentric circles having their conformed center on photodetectors 20 and 22, thus making the separation angle zero. Consequently, the transmitting light 21 can be detected by the 2-divided photodetector 22 while the diffracted light 19 can be detected by the 4-divided photodetector 20. Then, the magneto-optical signal is obtained from the output difference between these photodetectors. By this method, without providing a signal detecting system separately, and without coming under the influence of variations of a source of light in wavelength, the miniaturization with lighter weight and high speed access capability of the device can be contrived. |
