| 摘要 |
PURPOSE: To effectively eliminate crosstalk from the neighboring tracks and to thereby realize a stable high-density recording by shielding the peripheral luminous flux in the vertical direction to the track of the return luminous flux from a recording medium by using an opening with a specified width. CONSTITUTION: The return light from a magneto-optical disk 5 is collimated through an objective lens 4 to be guided to a light detector 7 through a condensing lens 6. At this time, an opening 12 given by a relation: 0.74-0.12.(d1/p)<B1/A 1<1.09-0.21.(d1/p) is disposed in the vicinity of the pupil of the light receiving system in the far field region by more than 8.(FN0 )<2> λ away from the focal plane of the light receiving system in the optical path between the objective lens 4 and the condensing lens 6, where A1: diameter of the luminous flux, B1: width of opening, d1: optical spot diameter multiplied 1/e<2> , p: track pitch, FN0 : effective F number of the detection optical system, and λ: wavelength of the optical flux. Through thgis, the peripheral luminous flux including much crosstalk in the radial direction vertical to the track of the return light is shielded to prevent its arrival at the optical detector and to reduce the crosstalk. |
