| 摘要 |
PROBLEM TO BE SOLVED: To provide a reproduction pickup device, with which short pit signals can be simultaneously read from a lot of tracks. SOLUTION: This device is composed of an optical radiation system having an objective lens with the prescribed number of apertures for forming an irradiated area narrowed to an almost diffraction limit in the extending direction of tracks by irradiating a plurality of adjacent tracks on a recording plane with the light beam of a prescribed wavelength, optical image formation system for forming a real image at a recording section due to the reflected light of the light beam with a prescribed lateral magnification, and photodetecting means having a plurality of photodetectors arranged almost vertically to the tracks of the real image at the recording section. In this case, concerning photodetectors 38a-38c, width (d) of each real image in the extending direction of the track has a length within the range shown by d<=1.2×α×λ/NA (α expresses a prescribed lateral magnification of the optical image formation system, NA expresses a prescribed number of apertures on the objective lens and λ expresses a prescribed wavelength of the light beam) and the photodetectors 38a-38c exist at the positions corresponding to a pitch (q) of tracks for the real image shown by q=p×α (p) expresses a prescribed track pitch of the optical information recording medium and αexpresses a prescribed lateral magnification of the optical image formation system} on the surface of the real image. |
