A multi-channel multiplexing method for a disc storage medium includes: S1) recording holograms at holographic positioning marks of the storage medium by a reference light beam and a signal light beam, S2) rotating the storage medium in a circumferential direction and repeatedly performing step S1 until the holograms have been recorded at all the holographic positioning marks on optical tracks, S3) translating the storage medium to switch an optical head to another optical track, S4) repeating steps S1-S3 until recording of one cross channel is completed, S5) changing a relative angle of the center of the storage medium with respect to the optical head, and repeating steps S1-S4 to complete recording of another cross channel, S6) repeating steps S1-S5 until recording of all cross channels is completed, and S7) reproducing the holograms at any channel or recording position of the storage medium by using the same beam of reference light.

The present invention relates to a method for accurately detecting and controlling a position of an optical head. According to the present invention, by utilizing the narrow shift selectivity of a spherical reference beam shift multiplexing technology, a control area that includes an x-direction position control unit and a y-direction position control unit and that is separated from a data area is formed in a storage medium. Like the data area, holograms of special patterns are recorded in the control area, when the data is read, information in the control area is read first, and the position of the optical head relative to the hologram in the data area can be detected in the x direction and the y direction respectively according to the information read by the hologram in the control area, so that reference light is controlled to the correct position shown by the address.

An optical recording medium includes a light-receiving surface that receives incident light and at least three information signal layers on which information signals are to be optically recorded. Among the at least three information signal layers, the information signal layer closest to the light-receiving surface has a reflectance in a range of 4% to 11%.

An optical recording medium includes a plurality of information signal layers on which information signals are to be optically recorded. Among the plurality of information signal layers, the information signal layer closest to the light-receiving surface has a reflectance of more than 4%.

An optical recording medium includes a plurality of information signal layers on which information signals are to be optically recorded. Among the plurality of information signal layers, the information signal layer closest to the light-receiving surface has a reflectance of more than 4%.

An optical disk drive and a digital servo method for the optical disk drive includes controlling functions of the optical disk drive with a microprocessor. Low-pass filtered and gain adjusted versions of individual photodetector output signals resulting from an illumination of an optical disk are received. Versions of the individual photodetector output signals are digitized to produce digital signals. A focus control signal and/or a tracking control signal is determined through at least one servo algorithm executed by a digital signal processor based on a focus error and/or tracking error, respectively, determined from the digital signals. The digital signal processor is an integrated circuit structured and arranged for manipulation of digital signals in accordance with programmed commands, and in a manner that operates faster than the microprocessor.

An optical recording medium includes a plurality of information signal layers on which information signals are to be optically recorded. Among the plurality of information signal layers, the information signal layer closest to the light-receiving surface has a reflectance of more than 4%.