Abstract: A wobble signal detection circuit is provided for an optical disk apparatus which detects a wobble signal by focusing a light beam into a spot on a pregroove on an optical disk during recording of data onto and reproduction of data from the optical disk, and includes a photodetector which detects first and second lights from first and second portions of the spot, respectively, and outputs first and second detection signals corresponding to respective power levels of the first and second detection lights. The wobble signal detection circuit includes: a sample-and-hold circuit sampling and holding the first and second detection signals output from said photodetector during the recording of the data onto the optical disk; lowpass filter means for reducing noise components of the respective first and second detection signals; and subtraction means for calculating a difference between the first and second detection signals respectively output from said lowpass filter means so as to obtain the wobble signal.

Abstract: A signal processing circuit generating a digital signal based on an input pulse signal is provided, which circuit includes a clock pulse output circuit which outputs clock pulses having one of positive and negative polarities for a period which includes a pulse of the input pulse signal, a counter circuit which counts the clock pulses, and an output circuit which outputs the digital signal based on a counted value of the counter circuit.

Abstract: An optical disc apparatus provided with an automatic power control circuit which controls power of laser light by obtaining a difference between a value detected by a front monitor 6 and a target value individually for reproduction power and for recording power includes: a detector 7 for detecting light reflected from an optical disc, a sample-hold circuit 26 which performs on an output of the detector 7 a sample-hold operation at the timing of the reproduction power; and a microcomputer 29 which computes a reference value from the reflected light of the reproduction power at the timing just before the start of a recording operation after receiving a recording command until opening of a recording gate, and at the time of recording operation an intensity of reflected light on which a sample-hold operation is performed is compared with the reference value to correct a target value of the reproduction power.

Abstract: A tilt detection system includes an optical disk having a series of data recorded therein, the series of data having a pulse width smaller than the minimum pulse width of data recorded in an ordinary optical disk; a reproducing part reproducing a signal from the optical disk by emitting a light beam onto the optical disk; and a tilt detecting part detecting a tilt of the light beam with respect to the optical disk based on a reproduced RF signal provided by the reproducing-part when the series of data having the smaller pulse width is reproduced.

Abstract: A tilt detection system includes an optical disk having a series of data recorded therein, the series of data having a pulse width smaller than the minimum pulse width of data recorded in an ordinary optical disk; a reproducing part reproducing a signal from the optical disk by emitting a light beam onto the optical disk; and a tilt detecting part detecting a tilt of the light beam with respect to the optical disk based on a reproduced RF signal provided by the reproducing part when the series of data having the smaller pulse width is reproduced.

Abstract: In this optical disk device, a reflected light of a light beam reflected from a pre-pit-formed side of a track wobbled on a disk is detected as a first detection signal. A reflected light of the light beam reflected from the other side of the track is detected as a second detection signal. The first detection signal and/or the second detection signal are/is amplified with a gain(s) so set that a peak value of a wobble signal component of the first detection signal coincides with a bottom value of a wobble signal component of the second detection signal.

Abstract: An optical disk device which performs data recording and reproduction with regard to an optical disk on which pre-pit information for specifying an address is formed. An optical disk is irradiated with a laser beam and return light from the optical disk is detected by two photodetectors which are disposed in the radial direction. After the levels of two signals from the photodetectors are limited, a difference between these signals is calculated. Due to the limitation of the levels, noise during the recording power period is removed so that pre-pit information during the reproducing power period, namely during the space period, is extracted. Further, by calculating a difference between the two signals from the photodetectors, pre-pit information during the recording power period is extracted.

Abstract: An optical disk apparatus capable of adjusting a focus servo and the like by precisely detecting a jitter amount. Light reflected from an optical disk is converted into an RF signal in an optical pickup and amplified by an RF amplifier before being supplied to an equalizer. The boost amount of the equalizer is set to zero during adjustment and set to a predetermined finite value (e.g., +20 dB) during normal recording and reproducing. By first setting the boost amount to zero, the delay characteristics of the RF signal from 3T to 11T are flattened such that an accurate jitter amount can be determined based on the integrated value of the phase differences of 3T to 11T, thereby allowing the optical pickup to be adjusted so as to minimize the jitter amount.

Abstract: A signal processing circuit generating a digital signal based on an input pulse signal is provided, which circuit includes a clock pulse output circuit which outputs clock pulses having one of positive and negative polarities for a period which includes a pulse of the input pulse signal, a counter circuit which counts the clock pulses, and an output circuit which outputs the digital signal based on a counted value of the counter circuit.

Abstract: An optical disk apparatus for performing recording and reproduction of information on an optical disk is disclosed. The optical disk has a sector format which consists of a sector mark area in which a sector mark is recorded and an address area in which a plurality of VFO segments and ID segments are alternately provided. The apparatus comprises a sector mark detector, a read gate controller, a PLL controller and an address information detector. The sector mark detector detects the sector mark. The read gate controller controls a read gate to be opened and closed. The read gate enables readout of information from the VFO segment when it is opened. The PLL controller initiates synchronization of a signal read from the VFO segment with a PLL in response to the opening of the read gate. The address information detector detects an address identifier recorded in the ID segment.

Abstract: An optical disk apparatus having an optical head for reading and writing signals on an optical disk and a signal processing unit for performing predetermined signal processing on the signals is disclosed. The apparatus includes a first controller, a second controller, a detector, and an adjuster. The first controller controls the optical head to write a predetermined signal on a predetermined area of the optical disk with various levels of recording power of the optical head. The second controller reproduces the predetermined signal written on the predetermined area of the optical disk. The detector attempts to detect a predetermined signal pattern having a predetermined period from the reproduced signal with different slice levels. The adjuster determines a resolution of the reproduced signal in accordance with a slice level with which the signal pattern can be detected and automatically adjusts the recording power of the optical head based on the determined resolution.

Abstract: A hard disk drive is disclosed in which the disk has tracks each divided into alternating data sectors and servo sectors, with the control data such as track addresses on the servo sectors being normally recorded more stably than the main data on the data sectors. In order to obtain read pulses representative of the peaks of the output waveform of a transducer, this waveform is directed on one hand into a differentiator circuit and thence into a wave shaping circuit for the provision of data pulses which rise and decay in synchronism with the peaks of the transducer output waveform. On the other hand, the transducer output waveform is sent into a gate pulse circuit, in which the waveform is compared with a reference signal in order to provide gate or window pulses. A logic circuit is provided for ascertaining whether the data pulses rise and decay within the durations of the gate pulses and, if they do, for producing read pulses indicative of the rises and decays of the data pulses.