Abstract: A liquid crystal driving signal generating apparatus comprises a PWM signal generator, a low pass filter for limiting a frequency band of a PWM signal outputted from the PWM signal generator, a liquid crystal panel connected to an output of the low pass filter, and a control means for controlling the PWM signal generator. The control means controls the PWM signal generator such that the PWM signal generator generates a PWM signal with a duty ratio corresponding to a refractive index to be set in the liquid crystal panel.

Abstract: Disclosed is a disc player for obtaining a read signal from an optical disc having sectors including land and groove tracks and ID regions, preformatted at given angular spatial intervals, which demarcate the sectors and are segmented, in the track extending direction, into two regions, each segmented region including a plural number of recording regions and non-recording regions, which are alternately and radially arrayed while being radially shifted by approximately half a track pitch from the tracks of the sectors adjacent to the segmented regions, each recording region containing record position information recorded therein having predetermined time durations.

Abstract: A signal compensating apparatus is an apparatus for compensating a control signal which is generated on the basis of a light beam reflected by an optical recording medium and which includes information with respect to a relationship between a spot of the light beam and a track of the optical recording medium. The signal compensating apparatus has: a detecting device for detecting a damaged part of the control signal, which is caused by a defect of the optical recording medium or an obstruction existing on an optical path of the light beam or on the optical recording medium; a replacing signal generating device for generating a replacing signal whose level gradually varies so as to connect a level of a first normal part of the control signal immediately before the damaged part with a level of a second normal part of the control signal immediately after the damage part; and a replacing device for replacing the damaged part by the replacing signal.

Abstract: A servo control apparatus for performing a feedback control to an analog controlled system, includes an error generating device that generates a digital error corresponding to a difference between a desired value and a feedback value corresponding to a controlled variable of the analog controlled system, a control device that generates a digital manipulated variable, and a digital-to-analog converting device that converts the digital manipulated variable into an analog manipulated variable for driving the analog controlled system. The control device includes a disturbance estimating device that estimates a disturbance applied to the analog controlled system by carrying out a digital estimating process by using the digital manipulated variable and the digital error and generates a digital compensated variable corresponding to the estimated disturbance, and a manipulated variable generating device that generates the digital manipulated variable by using the digital error and the digital compensated variable.

Abstract: An optical pickup for irradiating a light beam onto an information recording medium and receiving a light reflected by the medium, includes a light source for emitting a light beam, and a liquid crystal panel for diffracting the light beam to produce a main beam and a plurality of sub-beams to be irradiated on the medium. The liquid crystal panel included a first area in which a first group of grating patterns with predetermined pitches is formed and a second area in which a second group of grating patterns having the predetermined pitches is formed, and the first group of grating patterns and the second group of grating patterns are arranged on a plane with a gap area formed between the first area and the second area so as to form an integrated grating pattern.

Abstract: A repeat control apparatus is installed in an information reproducing apparatus. The repeat control apparatus performs a repeat control on a control signal. The control signal includes control information to be used for controlling reproduction of recording information from a recording medium. The control signal is generated by using a light beam reflected by the recording medium. The repeat control apparatus has: a storage device for storing the control signal; a detecting device for detecting a damaged part of the control signal; a generating device for generating a compensation signal to compensate the damaged part of the control signal; a storing control device for storing the compensation signal, instead of the damaged part of the control signal, into the storage device; and a repeat control device for performing the repeat control by using the control signal and the compensation signal stored in the storage device.

Abstract: An optical pickup includes: a light source, an object lens, and an aberration correction unit for correcting aberration by giving a phase difference to a light beam. The aberration correction unit corrects astigmatism caused by an optical system of the optical pickup.

Abstract: A searching method for an information record medium has: an initial value data preparing process of (i) performing a search for a plurality of sampling positions arranged in a radial direction on the information record medium, (ii) actuating a tilt servo to correct an error due to a tilt of an optical axis of a light beam emitted onto the information record medium from a normal line of a surface of the information record medium at each of the sampling positions, (iii) extracting a tilt correction amount after the tilt servo is stabilized for each of the sampling positions and (iv) storing the extracted tilt correction amount in relation to respective one of the sampling positions corresponding to the extracted tilt correction amount into a memory as initial value data of the tilt correction amount in advance; an initial value determining process for determining an initial value of the tilt correction amount at a search target position of the search when the search is to be performed, on the basis of a content

Abstract: The present invention is intended to reliably achieve a locked PLL even with a short VFO field to correctly perform subsequent reproduction of information data. A PLL circuit of the present invention is supplied with a composite signal composed of a repetitive signal including a pulse train of a constant duty ratio and a random signal including a pulse train allowing variations in duty ratio, where the two signals are arranged in time series. The circuit is provided with a VCO for generating an output signal having a frequency according to a control signal, a PFC for comparing the repetitive signal with the output signal in terms of phase and frequency to generate a phase frequency error signal, a PC for comparing the random signal with the output signal to generate a phase error signal, and loop filters for extracting predetermined band components of the phase frequency error signal and the phase error signal to generate the control signal.

Abstract: A CPU is provided for producing a control signal. In accordance with the control signal, a modulated signal modulated in pulse width by the control signal is produced. The modulated signal has a predetermined duty ratio based on the control signal. A liquid crystal driving signal having the duty ratio based on the modulated signal is produced. The CPU is for producing the control signal for setting the duty ratio in accordance with a refractive index at each of the unit electrode of the liquid crystal panel.

Abstract: Focus control apparatus in a reading apparatus for reading a multi-layered disk having information recorded on a plurality of recording surfaces thereof. The focus control apparatus includes a signal generating system for generating an acceleration signal for forcing the objective lens to move in the optical axis direction of the light beam and a deceleration signal for braking the objective lens which has been forced to move. The apparatus further includes control circuit for supplying a lens driving system with the acceleration signal and the deceleration signal as the driving signal in response to a switching instruction for switching a recording surface from which information is to be read, and for supplying the driving system with the focus error signal as the driving signal after the generation of the deceleration signal, to focus the light beam on a target recording surface.

Abstract: An apparatus for reproducing a digital signal which converts a signal read from a recording medium on which a digital signal is recorded into a series of sample values with an A/D converter, detects a phase error from the series of sample values, generates a gain phase error signal by providing the phase error with a predetermined gain, corrects the phase of a clock signal based on the gain phase error signal, and uses the clock signal with the phase thereof corrected as a sampling clock.

Abstract: An apparatus for reproducing record information of a multiple-layered optical disc is provided with: an optical pickup having a light source for emitting a reading light, an objective lens for condensing the emitted reading light onto one of the information record layers, a focus actuator for moving the objective lens in a focus direction, and a light-detection device for detecting the reflected reading light and outputting a light detection signal; a focus error generation device for generating a focus error signal; an acceleration/deceleration signal generator for generating and outputting to the focus actuator an acceleration signal to accelerate the objective lens in the focus direction and a deceleration signal to decelerate the objective lens in the focus direction; an inter-layer distance measurement device for measuring an interlayer distance between the information record layers of the multiple-layered optical disc; and a controller for measuring a time duration since the acceleration signal is gener

Abstract: A tilt servo controlling apparatus is provided with: an optical pickup for emitting a light beam onto an optical record medium and detecting a reflection light from the optical record medium to thereby output a detection signal; a level detecting device for detecting a level of the detection signal outputted by the optical pickup; a tilt error correcting device for correcting a tilt error due to an aberration, which is generated by a tilt angle between (i) a normal line of a surface of the optical record medium at a position irradiated with the light beam and (ii) an optical axis of the light beam; and a tilt error correction controlling device for outputting a control signal to control a correction amount of the tilt error correcting device, by giving a variation to the control signal on a time base and adjusting the control signal so that the level detected by the level detecting device be optimized with respect to the variation of the control signal.

Abstract: A tilt servo apparatus in an optical disc reproducing apparatus operates promptly and certainly when reading recording information of an optical disc recorded at high density. The tilt servo apparatus is used in an optical disc reproducing apparatus having an optical pickup including a liquid crystal panel for an aberration correction on which a transparent electrode is formed and divided into segments of predetermined shapes, and irradiating a laser beam via the liquid crystal panel for the aberration correction and the objective lens, and receiving an obtained reflection light. The tilt servo apparatus has: tilt detecting for detecting a signal corresponding to a tilting angle in a radial direction between the information recording surface of the optical disc and an optical axis of the objective lens; and a driving circuit for variably driving voltages which are applied to the divided portions of the liquid crystal panel, respectively.

Abstract: A spindle servo system roughly adjusts a rotational speed of a spindle motor for rotationally driving an optical disk at a specified speed in an optical disk player for reproducing digital data composed of run length limited codes and synchronizing signals, wherein the run length limited codes are restricted between a minimum run length and a maximum run length, and wherein the synchronizing signals are composed of a maximum bit pattern with a run length longer than the maximum run length and an additional bit pattern disposed just before or after the maximum bit pattern with a run length longer than the minimum run length and shorter than the maximum run length, the spindle servo system.

Abstract: A cycle slip detector of the invention has first and second comparators. The first comparator determines that the value of a phase error signal being supplied thereto is larger than a first threshold value near a maximum value possibly taken by the phase error signal, and responsively generates a first determining signal. The second comparator determines that the value of the phase error signal being supplied thereto is smaller than a second threshold value of a minimum value possibly taken by the phase error signal, and responsively generates a second determining signal. The cycle slip detector generates a cycle slip detecting signal when the first determining signal and the second determining signal generate in succession. By applying the cycle slip detector as mentioned, it is possible to provide a phase locked loop circuit having a wide frequency range in which a withdraw or pull-in operation is permitted.

Abstract: Disclosed is a digital PLL circuit which can permit voltage level conversion using pulse width modulation by a PWM circuit to thereby ensure lower consumed power and a lower implementation density even when the transitional change of the phase error signal is not constant. A phase error signal is obtained based on sample values acquired by sampling a read signal read from a recording medium, and an average phase error signal corresponding to the average value of this phase error signal is obtained. Then, this average phase error signal is sampled and held at a predetermined clock timing to acquire a sampled average phase error signal which is in turn subjected to pulse width modulation for each mentioned predetermined clock timing. A clock signal whose oscillation frequency corresponds to the average voltage level of the resultant pulse width modulation signal is produced as the aforementioned reproduction clock signal.

Abstract: A disk discriminating method and disk discriminating apparatus accurately discriminate plural types of disks with different recording densities. While a disk is rotated by a constant number of rotations, a recorded signal is read from the disk to acquire a read signal, one of the maximum period, minimum period, maximum inversion interval, minimum inversion interval and average frequency of the read signal is detected, and the type of the disk is determined in accordance with the detected value. This structure needs only a simple circuit, and no special mechanism, to be added to a disk player.

Abstract: Disclosed is a laser diode driving apparatus in a optical information recording and reproducing apparatus by which the bottom power of a laser beam for the information recording and reproducing may be maintained stably at a target value. A bottom power corrected value is obtained by multiplying the peak power of a laser beam for the information recording by a predetermined coefficient. Then, the bottom power corrected value is added with a target bottom power to set the summed value as a corrected target bottom power. The bottom level of an optical power detection signal is subtracted from the corrected target bottom power to provide the remaining value as an error signal. The bottom power of the laser beam is adjusted on the basis of the error signal.