Ricoh Company, Ltd.

Tatsuaki Sakurai

Masaaki Sofue

Hiroshi Gotoh

Ikuo Maeda

Isamu Shibata

Ryuuji Kudoh

Ryuuji Kudou

Ryuji Kudo

The present invention provides a large scale integrated circuit (LSI) for calculating servo signals (e.g., a focusing signal, a tracking signal, etc.) from the output signals received from a plurality of photo detectors, as used within an optical disk apparatus. The invention provides a switching circuit and a gain changing circuit coupled to the LSI such that a single LSI may be used for at least two different photo detector configurations as may be found in at least two different pick-up devices.

Signal operational circuit for a multi-beam pick-up device

In order to accurately detect a tracking error signal, the position of a sub-beam Bs1 with a lower shading rate is located at a position ahead of the position of a main beam Bm in the recording direction of an optical disk, and the position of a sub-beam Bs2 with a higher shading rate is located at a position behind the position of the main beam Bm in the recording direction of the optical disk. Therefore, the unequal amount of optical information created by the different shading rates is counterbalanced by the fact that the portions of the optical disk where the sub-beams Bs1 and Bs2 are directed have different reflective rates. Accordingly, the amount of optical information from each sub-beam received by the tracking error signal photo detector is made equal, and the tracking error signal can be accurately detected.

Optical pickup apparatus for accurate detection of a tracking error

A layer beam controller for an optical storage apparatus includes a laser beam generator, a laser beam power varier for varying the laser beam power to first, second, and third power levels, a memory for storing predetermined reference values including first reference values corresponding to the first power level and second reference values corresponding to the second power level, a light amount detector for detecting a light amount of the laser beam, a laser beam power corrector for correcting the laser beam power at the respective power level by comparing the light amount and a corresponding one of the predetermined reference values selected by a type of the compact disk in operation in the optical storage apparatus. The laser beam controller further includes a power level assigner for assigning the first, second and third power levels based on the type of disk.

Method and apparatus for changing laser beam power of an optical storage

A servo method in a multibeam optical pickup in which, at the time of a recording mode, a record information is confirmed and reproduced by a beam for reproduction while the record information is written by a beam for record, and the record information is reproduced by the beam for reproduction at the time of a reproducing mode, comprises the steps of detecting a focus servo signal and a track servo signal with respect to each of the beams for record and reproduction reflected by an optical disk; performing focusing and tracking operations based on the focus servo signal and the track servo signal provided by the beam for record at the time of the recording mode; and performing the focusing and tracking operations based on the focus servo signal and the track servo signal provided by the beam for reproduction at the time of the reproducing mode. In another servo method, the focusing and tracking operations may be performed according to the recording and reproducing modes. An optical pickup comprises a detector for detecting respective track error signals with respect to the preceding and subsequent beams; a tracking control device for performing a tracking servo control by the track error signal detected based on one of the beams; and a tangential control device for performing a tangential servo control by the track error signal detected based on the other of the beams.

Multibeam optical pickup and servo method thereof

A multi-beam optical pick-up for use in an optical disc system includes a light source for emitting two light beams which are focused onto an optical disc to form two light spots thereon. The pick-up also includes an optical system to receive light reflected from the optical system and to divide the reflected light into a first light beam and a second light beam. Also provided in the pick-up are a first detector for detecting an opto-magnetic signal and a focusing error signal from the first light beam and a second detector for detecting a tracking error signal for the two light spots formed on the optical disc with respect to a desired recording track thereof.

Multi-beam optical pick-up

A semiconductor laser control apparatus comprises a light receiving part for receiving a laser beam emitted from a semiconductor laser, a comparator for comparing an output signal of the light receiving part and a reference signal having a level corresponding to a desired target value of the optical output, a clock generator for generating clock pulses, an up-down counter for counting the clock pulses and carrying out one of an up-count and a down-count responsive to a first control signal, a control part for controlling the clock generator and the up-down counter responsive to an error signal from the comparator, and a driving part for driving the semiconductor laser by supplying a current proportional to a counted value of the up-down counter. The control part outputs the first control signal which determines one of the up-count and the down-count depending on whether an output signal level of the light receiving part is lower or higher than the level of the reference signal and outputs a second control signal which is supplied to the clock generator and variably controls a frequency of the clock pulses depending on an absolute value of the error signal.

Growing community of inventors

Kanagawa-ken, Japan

Tatsuaki Sakurai