Abstract: Servo error signal circuitry apparatus and methods are described. The difference between two bottom envelope signals SEbtm and SFbtm is calculated by a subtracter (40) to generate a difference signal (SEbtm?SFbtm). The difference signal (SEbtm?SFbtm) is input as an alignment signal (AL) to an equalizer (42) and as a basic tracking error signal to the positive input terminal of a second subtracter (52). On the other hand, the difference between two top envelope signals SEtop and SFtop is calculated by a third subtracter (48) to generate a difference signal (SEtop?SFtop). The signal K(SEtop?SFtop) obtained by multiplying a coefficient K with the difference signal using a coefficient multiplier (50) is input to the negative input terminal of the second subtracter (52). The difference signal {(SEbtm?SFbtm)?K(SEtop?SFtop)} output from the second subtracter (52) is used as an offset corrected tracking error signal.

Abstract: An optical disc device for changing intensities of light beams illuminated on an optical disc. The optical disc device comprises the following elements. A photo detecting device divided into a plurality of photo detectors is used for detecting the reflected light beams illuminated on an optical disc. A plurality of amplifiers is used for changing gains to respectively amplify the output signals of the photo detectors when recording and reproducing on/from the optical disc. A calculating device is used for calculating the output signals of the amplifiers to generate the servo signals. By adding the correction offset signals for correcting the offset voltages of the amplifiers and the photo detectors to the amplifiers, the correction offset signals are amplified. It is, therefore, not necessary to change the correction offset voltages even though the gain of the amplifier is changed and not necessary to change the offset voltage and is independent of the gain-switching of the amplifier.

Abstract: A method of tracking error correction, primarily for utilization in optical disc drives using single beam optical pick-up heads. Delinearization in the tracking servo of a single beam optical pick-up head, contributed to by inherent design properties, is minimized by extracting a value proportional to a tracking error signal offset component from a tracking servo demand signal, applying a scaling factor to match the scaling applied to the tracking servo demand signal with scaling applied to the amplified tracking error signal, and subtracting the product of this function from the source signal i.e. the tracking error signal. The modified source signal, following this operation, has a reduced order of tracking error offset.

Abstract: An optical disk device is provided that can realize favorable recording/reproduction of signals on/from an optical disk having a plurality of signal planes arranged in proximity to each other. In this optical disk device, a hologram (4) is divided into n(n?2) regions Ak(k=1, 2, . . . , n) by a straight line that intersects with an optical axis, and a photodetector (7) is divided into at least two regions A and A?. Light emitted from a light source (1) is focused on a signal plane (6a) or (6b) included in a plurality of signal planes of the optical disk by an objective lens (5). Light reflected from a first signal plane (6a) and light reflected from a second signal plane (6b) pass through the objective lens (5) to turn into light beams a and a?, respectively, that enter the hologram (4).

Abstract: A circuit for generating a compensation signal (TC) to compensate a tracking error (TE) swing in a servo control system, the TC signal being pre-defined in accordance with an algorithm for generating a TE signal, the circuit comprising a set of peak detection devices corresponding to a set of photo-detector elements formed in a photo-detector, each of the peak detection devices detecting an amplitude of an optical detection signal derived from a corresponding photo-detector element, a set of amplifiers of a same gain corresponding to the set of peak detection devices, the gain being selectable between an inverting and a non-inverting terminals, a set of gain selection signals corresponding to the set of amplifiers to select one of the inverting and non-inverting terminals in accordance with the pre-defined TC signal, and an adder for adding the amplitudes that are gain selected.

Abstract: An optical semiconductor device comprising an emitted beam branching section (61) which branches an emitted light beam from a laser device (51), a reflected light beam branching section (71) which branches a reflected light beam from an information recording medium (3) into light beams different from each other in focused state, servo signal sensing photodetectors (43, 45) which receive the branched reflected light beam in a defocused state, a first diffraction grating provided in the emitted light beam branching section for diffracting the reflected light beam having passed through the reflected light beam flux branching section, and a signal sensing photodetector (47) which receives the reflected light beam diffracted by the first diffraction grating.

Abstract: An optical disk apparatus has a first optical system having an objective lens with a first NA, a second optical system having an objective lens with a second NA lower than the first NA, an addition mechanism for adding focus error signals detected by the first and second optical systems, and an alignment mechanism for aligning the objective lens in accordance with the addition result of the addition mechanism.

Abstract: An optical disk apparatus includes an optical detector which has light receiving areas divided nearly concentrically with an optical beam and outputs a signal corresponding to the amount of the reflected light from an optical disk. A surface vicinity detecting section adds up signals from all the light-receiving areas of the optical detector and outputs a detection signal. The detection signal continuously varies so as to have one maximum level while a beam spot of the optical beam moves from the surface of the information medium to the information plane. An information plane detecting section judges that the focus or the beam spot of the optical beam comes closer to the information plane of the optical disk by detecting the gradient of the detection signal. An approach of a condensing lens and the optical disk is judged based on the judgment results, and thus a collision of the condensing lens and the optical disk can be prevented.

Abstract: A circuit to improve the SN characteristic of a tracking error signal. This tracking error detection circuit is formed as a push-pull system utilizing a quadrant type photo-detector and provided with 4 gain control amplifiers 20, 22, 24, and 26, 4 bottom envelope circuits 28, 30, 32, and 34, a pair of subtracting circuits 36 and 38, adding (subtracting) circuit 40, offset circuit 42, and gain control circuit 44. Bottom envelope circuits 28, 30, 32, and 34 are configured with a capacitor-type peak-hold circuit, for example, whereby bottom envelopes of RF signals SA, SB, SC, and SD given from light receiving areas A, B, C, and D of a photo-detector via gain control amplifiers 20, 22, 24, and 26 are detected, and bottom envelope signals SAbtm, SBbtm, SCbtm, and SDbtm representing the waveforms of the respective bottom envelopes are output.

Abstract: An optical disc drive waits to receive a command to perform a function on optical media in the disc drive. The optical media includes a pitted premastered area that cannot be overwritten and a grooved user-writeable area that can be overwritten. Once a command is received, one portion of the disc drive processes the command while another portion of the disc drive monitors the processing of the command and waits until the command is processed. If an error condition is detected while processing the command, the disc drive generates an event request such as a notify event request, a focus event request, a spin event request, and a tracking event request. When an event issues, the disc drive interrupts processing of the command and attempts to recover from the error condition. The state of the disc drive when the requested event was received is saved before attempting to recover from the error condition.

Abstract: A light beam from a light source is introduced to a grating element of a pickup device to create zero order diffracted light, ±first order diffracted light, and ±second order diffracted light. An irradiation system focuses the zero order, ±first order and ±second order diffracted light onto tracks extending on a recording surface of an optical recording medium to form spots. A spot of the zero order diffracted light is formed on a target track, spots of the ±second order diffracted light are formed on tracks adjacent to the target track, and spots of the ±first order diffracted light are formed midway between the spots of the ±zero order and ±second order diffracted light. An optical system guides returning light reflected from the spots to an optical detector. The optical detector has independent light-receiving elements for receiving the returning light. A servo signal calculator creates an error signal based on the output signals from the optical detector.

Abstract: A circuit for tracking error signal detection on an optical storage medium, which has a plurality of digitizers, a plurality of logic comparators and a difference amplifier, is disclosed. The circuit involves summing the signals to be compared and obtaining a delay signal via a delayer. Therefore, the phase difference of the signals is detected via the delay signal to obtain the tracking error signal of the optical storage medium.

Abstract: After making such adjustment that an a main push-pull signal MPP offset can be made zero when a main beam is positioned at the center of a main photoreceptor, using electric signals E and F photoelectrically converted by one of two two-divided side beam photoreceptors and electric signals H and G photo-electrically converted by the other thereof, a side push-pull signal SPP including a constant ? is determined for allowing respective (F??E) and (?H?G) offsets to be made zero and is calculated according to the formula, SPP?(F??E)+(?H?G). From this SPP signal and the main push-pull signal MPP, a differential push-pull signal DPP is then calculated, thereby allowing stable tracking control to be carried out, even during recording.

Abstract: A disc drive includes a tracking actuator, and determines when the tracking actuator is positioned off a formatted portion of optical media in the disc drive. The optical media includes a pitted premastered area that cannot be overwritten and a grooved user-writeable area that can be overwritten. Tracking control effort is monitored to determine when the tracking actuator is in the off-format condition and whether tracking good or tracking bad is detected within a predetermined time period. An absolute value of the tracking control effort is generated and the absolute value of the tracking control effort is filtered. An off-format condition is indicated if the filtered value of the tracking control effort is not within a predetermined threshold value.

Abstract: An error signal detection apparatus for an optical recording/reproducing system including a light source emitting a light beam and an objective lens focusing the light beam to form a light spot on a recording medium, the apparatus including: a photodetecting unit dividing at least a part of the light beam passed through the objective lens after being reflected/diffracted from an information stream of the recording medium into light beam portions, and detecting the light beam portions; and a signal processor detecting phase differences between detection signals from the light beam portions to detect a tangential error signal, a defocus error signal, and/or a radial tilt error signal.

Abstract: A method of arranging an optical pickup system on a deck of an optical recording and/or reproducing apparatus, which enables detection of a tracking error signal using one photodetector based on a three-beam method and by a differential phase detection method. The optical pickup system includes a light source, a diffractive optical element which diffracts a light beam incident from the light source and splits the same into at least three beams, a plate-type beam splitter which changes a propagation path of the light beam, and a photodetector including at least one main photodetector having at least four sections and a plurality of sub-photodetectors. The optical pickup system is constructed so as to have a reflecting mirror redirect the propagation path of the light beam emitted from the light source toward a recording medium.

Abstract: A photodetector and optical pickup device which comprises: a monitoring photodetection element (photodiode) 23 for receiving laser beams having different wavelengths from laser light sources; a light source-discriminating photoreceiver 24 represented by a photodiode (240) and a wavelength selection filter (241) for discriminating the wavelength spectra of the laser light sources; and a sensitivity regulation circuit (25) for regulating the sensitivity of the monitoring photodetection element 23 in response to the light source-discriminating photoreceiver 24.

Abstract: It is an object of the present invention to provide an optical pickup apparatus which is capable of supporting multiple wavelengths in a reduced size without using a combined prism. An apparatus includes light emitting means having a plurality of integrated light emitting portions for emitting laser beams of different wavelengths, the light emitting means being adapted to selectively emit one of the laser beams of different wavelengths; photodetecting means for detecting the laser beam; and an optical system for directing the laser beam emitted from the light emitting means to the disc, and for directing the laser beam reflected by the disc to the photodetecting means, wherein the light emitting means is positioned such that a straight line connecting respective light emitting points of the plurality of light emitting portions is coincident with a tangential line of a track on a disc to be reproduced.

Abstract: On an optical disc including a substrate on which pits having at least two different depths are formed, main information is recorded by the shape of the pits and additional information is recorded by the depth of the pit. It is possible to reverse polarity of a tangential push-pull signal dependent on the depth of the pit, and therefore it becomes possible to record information utilizing the depth of the pit. This improves recording density of the optical disc. Further, when information of the optical disc is to be copied, the information recorded by the depth of the pit cannot be copied. Therefore, unauthorized reproduction can be prevented.

Abstract: An optical disk apparatus of this invention includes a light source, an objective lens which focuses a laser beam output from the light source onto an optical disk, a hologram which divides an overlap region where, of reflected light components from the optical disk, a 0th-order light component and ±1st-order light components that are symmetrical with respect to the 0th-order light component overlap by the diameter of the 0th-order light component and also divides a non-overlap region where the 0th-order light component and ±1st-order light components do not overlap along the diameter and a radius perpendicular to the diameter, and a photodetector which independently detects reflected light components from the regions divided by the hologram.

Abstract: To stably carry out recording and reproducing to and from a high density optical disk without using a double servo in the optical disk using a high NA objective lens. A detection of a spherical aberration and a detection of a coma aberration in a radial direction are simultaneously performed, and the coma aberration generated with the offset of an objective lens 109 is corrected in real time, thus enlarging an allowable offset amount of the objective lens. In order to simultaneously detect the spherical aberration and the coma aberration, focal shift and tracking shift signals in an inside region and outside region of reflected light flux are detected respectively, and the differential signals are set as spherical aberration and coma aberration signals.

Abstract: Method for tracking in an apparatus for reading from and/or writing to an optical recording medium, and corresponding apparatus for reading from and/or writing to an optical recording medium. In order, in an apparatus for reading from and/or writing to an optical recording medium (18), to enable exact counting of the tracks of the optical recording medium (18) crossed by an optical scanning unit (16), it is proposed to derive a signal corresponding to the TZC signal (Tracking ZeroCross) and also a signal corresponding to the MZC signal (Mirror Zero Cross) from the output signal or the output signals (OUT1, OUT2) of a phase comparator (1) provided for tracking in accordance with the so-called differential phase detection method.

Abstract: A control system for controlling tracking and seeking in an optical disc drive for optical media with a pitted premastered area that cannot be overwritten and a grooved user-writeable area that can be overwritten. The control system determines whether an optical pickup unit is over the premastered or the writeable areas of the optical media by measuring peak to peak amplitude of a tracking error signal. Gains and calibration values are selected based on whether an optical pickup unit is over the premastered or the writeable areas of the optical media. Reading from and writing to the optical media is disabled while jumping tracks. Control of jumping tracks on the optical media includes controlling: jumping a single track on the optical media; jumping a specified number of tracks every specified number of revolutions of the optical media; auto jumpbacks, and jumping in forward or reverse directions.

Abstract: A system for controlling focus in an optical disc drive for optical media with a premastered area that cannot be overwritten and a user-writeable area that can be overwritten includes instructions for turning focus on and off; and for acquiring focus on the optical media in response to a command to acquire focus. The actuator arm is moved according to a sinusoidal ramp function to prevent exciting resonances in the actuator arm. The amount of push-away force used while moving the actuator arm can be adjusted to avoid overshoot. The integrity of a focus error signal is determined and an attempt to re-acquire focus is made if the focus error signal indicates a bad focus status.

Abstract: Device and method for detecting a non-writable region of an optical recording medium, wherein a read channel 1 signal and a read channel 2 signal are sliced at respective slice levels to produce header mask signals, and a header region which is a non-writable region is determined for the header mask signal taking the slice levels and written/unwritten regions ion the disk, whereby permitting stabilization of servos because servo error signals, such as a tracking error signal, and a focus error signal can be held exactly at a header region even if the servos are not stable, that prevents deterioration of a data quality in writing and reading, and permitting to shift an optical pickup to a desired position and accurate measurement of an amount of eccentricity because there is no influence of the header in a track jump and a disk eccentricity measurement.

Abstract: A method is designed for recording information on an optical disk in the form of a sequence of pits along a track of the optical disk.

Abstract: An object of the present invention is to provide an optical pickup apparatus which changes characteristics of a light-emitting device or hologram to reduce problems of track servo deviation due to scratches on a surface of an optical disc. By aligning a photoreceptive domain for focusing error signal (PDf) and a photoreceptive domain for tracking error signal (PDt), even in a case where scattering light made by a scratch in the tangent direction of a track of an optical disc reaches the photoreceptive domains, light diffracted in a HA+B domain of a hologram pattern does not enter into photoreceptive portion F or G of the PDt. Therefore, scattering of light which enters the PDf does not influence a tracking error signal (TES), so that the TES does not become abnormally large, and track servo deviation can be prevented.

Abstract: In a method and an apparatus for aberration correction according to the invention, aberration occurring in recording/reproducing information derived from causes such as thickness variation of a substrate, a tilt, a focus error and a tracking error is detected, and the aberration is corrected by correcting these causes.

Abstract: An optical disk pickup system includes an array of photodiodes 101 for converting photons reflected from an optical disk into a plurality of electrical signals each representing a channel. Driving circuitry 407, 408 drives at least one of the electrical signals as a current across a conductor of a flexible cable 403. A low impedance load 404 converts the electrical signal driven across the conductor as a current into a voltage for further processing.

Abstract: An optical pickup apparatus (10) for reading data from a plurality of tracks of an optical disc (34) at the same time by focussing spots (M, . . . ) of each light beam on a plurality of tracks, passing the reflected light beams of spots (M, . . . ) sequentially through an objective lens (30), a collimator lens (28), and a focus adjusting lens (50) in this order, and detecting the reflected light beams with photodiodes (52M, . . . ) disposed along a photodiode light reception plane (68). In order to make each reflected light become incident upon each photodiode (52M, . . . ), a case (72) and a bracket (78) are separated from a chassis (70), and support the focus adjusting lens (50) and the photodiodes (52M, . . . ) respectively. The case (72) and bracket (78) are made so that they can be fixed to the chassis (70) at optional positions in a predetermined area along a direction of the optical axis (66).

Abstract: A gain calibration device and method for differential push-pull (DPP) tracking error signals in an optical storage system is provided. The gain calibration method processes the synthesized gain (SPPG) of the sub beam in the DPP tracking error signal components with respect to the main beam. The calibration theorem resides in controlling the objective lens of the pick-up head to form a lens-shift or controlling the tilt of the objective lens relative to the optical disc to make the synthesized DPP tracking error signals generate a correspondingly signal variation owing to the optical path deviation. The synthesized gain is calibrated to make the signal variation a minimum value, and the calibrated synthesized gain is the optimum value.

Abstract: An optical pickup apparatus includes a detection unit detecting a light beam reflected/diffracted by the recording medium and passing through the objective lens by dividing the light beam into a plurality of light areas, and a signal processor detecting a difference between widths T1 and T2 indicating that first and second focusing signals are greater than a predetermined threshold value and a thickness signal of the recording medium by using the detected difference when an S-curve of a focus error signal detected by using detection signals of the light areas output from the detection unit is obtained by subtracting a second detecting signal from a first detecting signal or by subtracting the first focusing signal from the second signal. Thus, a spherical aberration due to a change in thickness of the recording medium can be corrected by driving a spherical aberration correcting device according to a thickness signal corresponding to the change in thickness of the recording medium.

Abstract: The present invention provides an optical pickup device that is resistant to noise in a signal or an RF signal outputted from each light receiving member. Current signals outputted from the light receiving members are converted into voltage signals by I/V converters. The voltage signals are then added up by an adder, and then the added voltage signal is attenuated by an attenuator, so as to obtain an RF signal having the same signal level as the voltage signal outputted from each I/V converter. The RF signal is then transmitted from the optical pickup device to a circuit substrate through a signal line.

Abstract: A tracking error detection apparatus includes a phase error detection unit for detecting a phase error of an output signal according to the amount of reflected light that is obtained when a light beam is applied to an information recording medium and a low-band pass unit for performing band restriction to obtain a tracking error signal from the phase error signal. The tracking error detection apparatus also includes a clock generation unit for generating a clock and a clock control unit having a frequency divider for generating a frequency-divided clock of the clock that is generated by the clock generation unit, wherein the clock control unit uses the frequency-divided clock as an operation clock for the tracking error detection apparatus. Therefore, the operation rate of each unit when generating a tracking error signal can be reduced, whereby a reduction in power consumption is achieved.

Abstract: A method for checking the existence of an optical disk using a focusing signal is provided. The method in accordance with the present invention prevents misjudgement of the existence of an optical disk which is caused by noise contained in a focus error signal or by the low reflection ratio of a disk.

Abstract: An optical pickup is provided which can read information from a plurality of recording mediums having different wavelengths without the need for a mixing prism. The optical pickup is comprised of a light emission part, a grating, a hologram and a light receiving part. The light emission part emits first and second laser beams having different wavelengths from each other. The grating generates a pair of sub-beams from the laser beam emitted from the light emission part. The hologram generates first and second high-order beams from the laser beam reflected by a recording medium to guide the high-order beams to the light receiving part. The light receiving part receives the first and second high-order beams generates a focus error signal and a tracking error signal which enables the information to be correctly read from the different recording mediums.

Abstract: The present invention makes it possible to control a writing light quantity by selectively using a light quantity detection result S0 (C+D) obtained from areas C and D at the back side in the direction of scanning with laser beams when data is recorded onto an organic dye type recording medium, such as a CD-R (compact disk recordable).

Abstract: The object of the invention is to provide a light receiving amplification element applicable to an optical pickup apparatus comprising a semiconductor two-wavelength laser element and one condensing lens. The light receiving amplification element is provided with a plurality of light receiving portions corresponding to different wavelengths, a plurality of trans-impedance type amplifiers connected to the light receiving portions according to the different wavelengths and adaptable to the different wavelengths and switching portion for switching output from the trans-impedance type amplifier according to each of the wavelengths.

Abstract: With a CD laser, a focusing search is carried out to detect a value CD-FE(pp) which is a difference between a maximum value and a minimum value of a focusing error signal, and to detect a value CD-AS which is a maximum value of a full-added signal. With a DVD laser, the focusing search is carried out to detect a value DVD-FE(pp) which is a difference between a maximum value and a minimum value of the focusing error signal, and to detect a value DVD-AS which is the maximum value of a full-added signal. The value that DVD-FE(pp) is divided by DVD-AS(max), is divided by the value that CD-FE(pp) is divided by CD-AS(max). According to whether the computed result by division is larger or not than a threshold value, it is determined whether the disk 100 is of a CD standard or of a DVD standard.

Abstract: In an optical disc apparatus for reading data from an optical disc, levels of photo-detecting signals outputted from a plurality of photo-detecting areas of a photo-detector are adjusted to be substantially even for canceling error components due to positioning error of the photo-detector on an optical pickup. Analogous signals outputted from the photo-detecting areas of the photo-detector are amplified by amplifiers and converted to digital signals by A/D converters. A processor takes the converted digital signals and adjusts gains of the amplifiers with using the digital signals.

Abstract: At a timing when a spot M of a main beam enters a defective area N of an optical disc, the tracking servo control is stopped, and the position the spot M of the main beam is held to the current position with respect to a radial direction of the optical disc, and, after a spot S2 of a rear sub-beam then exits the defective area N, the tracking servo control is resumed.

Abstract: Header regions are formed by dividing a groove or grooves. Each of the header regions is provided with two ID sections G-ID1, G-ID2 storing address information and a track center detection mark section, arranged between the two ID sections, so as to be used for detecting the track center.

Abstract: An information recording/reproducing apparatus includes an optical device, a photo-detector and a calculation unit. The optical device irradiates light beams, including one main beam and at least two sub-beams with respect to an information recording medium. The photo-detector receives return lights of the main beam and sub-beams to output light detection signals. The calculation unit produces a tracking error signal and a position information signal based on the light detection signals. The optical device irradiates the at least two sub-beams onto positions shifted to opposite sides of a center of the guide track, respectively, when the main beam is being irradiated onto a center of the information recording track. Thus, the apparatus produces the tracking error signal and the position information signal by utilizing a common optical system and a common signal processing system and thereby executes tracking servo control and random access processing with high accuracy.

Abstract: An apparatus for and a method of detecting a defocus error signal. First, second and third light receiving regions of a photodetector are arranged in a radial direction of a recording medium to independently perform photoelectric conversion with respect to incident light which is reflected/diffracted by the recording medium. A subtractor subtracts a sum signal of detection signals from the first and third light receiving regions and a detection signal of the second light receiving region to output a defocus error signal, to detect defocus and/or a change in thickness of the recording medium. The defocus error signal and a push-pull tracking error signal are compared in a state in which a predetermined amount of defocus is applied to a light spot to detect a seek direction of the recording medium having a land/groove structure.

Abstract: An optical pickup device for focusing a light beam includes a focus error detecting optical element which splits and leads return light to a photodetector. The focus error detecting element has an area quadrisected by two division lines defining a plane substantially perpendicular to the optical path of the return light for applying astigmatism to the return light in directions rotated by 90° from each other and for separating the return light into at least four by the respective quadrants. The photodetector has a plurality of spaced light receiving elements for receiving the separated return light, each receiving element has contour lines corresponding to the division lines on an image plane on which a light beam is shaped into a circular beam. The light receiving elements are comprised of two light receiving areas divided by a bisect line extending substantially in parallel with one of the contour lines.

Abstract: Light emitted from a laser is separated into a main beam, first sub beams, and second sub beams. The distribution intensity of each first sub beams is the same as that of the main beam. The distribution intensity of each second sub beam is different from that of the main beam. The sum of the focusing error signals relating to the main beam and first sub beams is a final focusing error signal. The difference between the tracking error signal relating to the main beam and the tracking error signal of each first sub beam is a final tracking error signal. The deviation of the thickness of the substrate of the disk and the radial tilt thereof are detected on the basis of the deviation of the zero crossing points of the focusing error signal and the tracking error signal relating to the main beam and each second sub beam.

Abstract: An apparatus generating a seek direction detecting signal includes a light dividing unit dividing an incident light beam into at least two beams having a main beam and a sub-beam so that at least two beam spots including a main beam spot and at least one sub-beam spot having an optical aberration, can be focused in the track direction of an optical disk, the light dividing unit providing that the direction of the optical aberration of the sub-beam spot can be the tangential direction of the optical disk, an optical detector unit, a first signal processing portion processing a track error signal from signals output from the optical detector, a second signal processing portion processing a track cross signal from the signals output from the optical detector, and a generator generating the seek direction detecting signal from the phase difference between the track cross signal and the track error signal.

Abstract: A tilt detecting apparatus of an information-recording medium having a photo diode for detecting a light reflected from an information-recording medium and outputting a light amount signal according to the detected light amount; and a calculating unit for calculating a radial tilt amount by using the light amount signal, wherein the photodiode is divided into a plurality of cells which are identified as regions according to a light amount of the reflected light, based on which a tilt signal is detected. A portion of the reflected light diffracted at the information-recording medium is detected by using the 8-divided photo diode, the region having a large difference in a light amount by the tilt and the region having a small difference in a light amount by the tilt in view of the characteristic of the reflected light are detected.

Abstract: In an optical disk recording device for projecting a recording light beam onto an optical disk to form 3T-11T pits in a land of the optical disk, timing to sample and hold a reflected light detection signal for tracking servo control is delayed behind timing to sample and hold the reflected light detection signal for wobble signal detection. Further, a sample-and-hold time period of the reflected light detection signal for tracking servo control is set to be shorter than a sample-and-hold time period of the reflected light detection signal for wobble signal detection. Such arrangements permit appropriate recording, even at high recording speeds, irrespective of residual optical axis deviations.

Abstract: A system for detecting a tracking error comprises a two-divided type light detector (2), LPFs (4a, 4b), first and second waveform generator (5a, 5b), first and second delay circuits (6a, 6b), first and second adders (7a, 7b) and a phase comparator (8). The detector (2) has two photo detecting elements (2a, 2b) disposed separately in the radius direction of an optical disc. The LPFs (4a, 4b) remove high frequency components from the outputs of the elements (2a, 2b). The first waveform generator (5a) generates a sine wave (B1) with amplitude corresponding to the output level of a signal (A1), which passed the LPF (4a). The second waveform generator (5b) generates a sine wave (B2) having the identical frequency to the wave (B1), with amplitude corresponding to the output level of a signal (A2), which passed the LPF (4b). The first delay circuit (6a) delays the wave (B1) by the prescribed amount of delay to form a sine wave (C1).