44 results about "Differential phase detection" patented technology

A controllable tilt servo adjusts a tilt angle between an optical disc and an object lens according to a control signal from a CPU. An optical electric integrated circuit (OEIC) generates a differential phase detection (DPD) signal according to light received through the object lens from the optical disc. A tilt search block receives the DPD signal and controls the tilt servo by adjusting the tilt angle between the optical disc and the object lens according to the DPD signal. By iteratively scanning pluralities of tilt angles, each plurality of angles having decreasing angle differences and being centered on the tilt angle having the lowest amplitude DPD signal, an optimal tilt angle having the lowest amplitude DPD signal can be found.

Optical receiver 300 uses two optical delay detectors 223 (set such that the delay times T are equal to symbol time and the phase differences are zero and 90 degrees) to receive an optical multilevel signal 215 and the output signals are A/D converted, thereafter subjected to retiming processes, and then subjected to a differential phase detection, thereby detecting a differential phase at a symbol center time point. In the receiver, the detected differential phase is integrated for each symbol and thereafter combined with an amplitude component obtained from a separately disposed optical intensity receiver, thereby reproducing an optical electric field. Thereafter, a wavelength dispersion compensation circuit (231) of a time period T is used to compensate for the wavelength dispersion of the transmission path. Moreover, an electric or optical Nyquist filter may be inserted to perform a band limitation, thereby enhancing the wavelength dispersion compensation effect.

An optical disk device in which data is written to or reproduced from an optical disk having an area which contains a header section and another area which does not contain a header section. When a track deviation of an optical pickup occurs, it is detected whether or not a signal representing the header section is contained in the return light signal from the optical disk. When a signal representing the header section is contained in the return light signal, it is determined that the optical pickup is located in an area which contains a header section and tracking is controlled through a push-pull method etc. On the other hand, when a signal representing the header section is not contained in the return light signal from the optical pickup, it is determined that the optical pickup is located in an area which does not contain a header section and tracking is controlled through differential phase detection etc.

A circuit for generating tracking error signal using differential phase detection, comprising a quadrant photodetector for receiving optical signal and inducting splitting signal A, splitting signal B, splitting signal C and splitting signal D, two adders for generating group signal (A+C) and group signal (B+D). A plurality of equalizers for receiving, equalizing and amplifying splitting signal A, splitting signal B, splitting signal C, splitting signal D, group signal (A+C) and group signal (B+D). A plurality of phase detectors for receiving the output of equalizers and comparing phase difference of splitting signal A and group signal (A+C), group signal (A+C) and splitting signal B, splitting signal C and group signal (B+D), and group signal (B+D) and splitting signal D, and outputting a plurality of adjustment signals respectively. A circuit for eliminating the phase difference by adding and subtracting some adjustment signals with same phase difference. A comparator for receiving and comparing the output of the circuit to obtain a tracking error signal.

A method and apparatus for controlling reproduction of an optical recording medium is disclosed. According to the method and apparatus, a moving direction of an object lens on a disc is detected from a slope of a differential phase detection (DPD) error signal in case that the tracking control of the disc is performed by the DPD error signal, and the tracking control is performed using the detected moving direction of the object lens. Thus, the proceeding direction of the object lens can be easily and accurately detected in the disc from which the detection of a mirror signal is not facilitated, i.e., in the disc whose tracking is controlled by the DPD error signal during reproduction. Since it can be easily discriminated whether the phase of the tracking error signal to be in a track-on state when a track servo is turned on is a land or a groove, the stability of the servo can be secured, and an automatic breaking can be achieved.

A differential phase detection device receives first through fourth detection signals from a photodetector and detects a differential phase signal therefrom, the differential phase detection device includes a slicer slicing and digitizing each of the detection signals with respect to a reference level. A synthesizer synthesizes the digitized detection signals and generates therefrom synthesis signals. A phase difference detector compares phases of the synthesis signals and outputs a first phase difference signal and a second phase difference signal. A matrix circuit processes the first and second phase difference signals to output the differential phase signal.

A Differential Phase Detecting (DPD) tracking error generating section generates a DPD tracking error signal from a plurality of sense signals supplied from an optical sensor. A Push Pull (PP) tracking error generating section generates a PP tracking error signal from a plurality of sense signals supplied from the optical sensor. The amplitude of each of the DPD tracking error signal and PP tracking error signal is adjusted suitably under the control of a CPU. The suitably adjusted signals are added by an adder, thereby generating a tracking error signal.

A photodetector detecting reflected light components from an optical medium, the photodetector including a first detector divided into eight sections detecting the reflected light components and converting the light components into electrical signals, a first calculating portion calculating a first tracking error signal from the electrical signals by a differential push-pull method, a second calculating portion calculating a first focusing error signal by an astigmatism method and calculating a second tracking error signal by a differential phase detection method from the electrical signals converted by the first detector; a second detector divided into four sections detecting the reflected light components reflected by the optical recording medium to convert the light components into electrical signals; and a third calculating portion calculating a second focusing error signal by the astigmatism method and calculating a third tracking error signal by the differential phase detection method from the electrical signals converted by the second detector.

A demodulator in a receiver has a multiple symbol differential phase detector which calculates phase differences between a received signal and received signals of 1, 2, . . . , N (Where N is an integer greater than 2) before so as to output the calculated results as N symbol differential phase detected signals. Further, a soft decision sequence estimating unit in this demodulator estimates a transmitted differential phase sequence according to the 1, 2, . . . , N symbol differential phase detected signals using a trellis diagram representing transitions of differential phase states of a transmitted signal and Viterbi algorithm and estimates soft decision demodulated data according to estimated transmitted differential phase sequence and the survival path metrics that transit into each state on the trellis diagram.

A tracking error signal detection device employing a differential phase detection method includes first and second differentiators which remove direct current components in first and second signal groups in which a phase difference between the first and second signal groups changes in accordance with a tracking error signal, and which differentiate the first and second signal groups, first and second analog/digital converters which sample and quantize signals output from the first and second differentiators, respectively, a Hilbert transformer performing a 90-degree phase shift on one of signals output from the first and second analog/digital converters, a delay circuit delaying one of the signals output from the second and first analog/digital converters by an amount of delay equal to that caused by the Hilbert transformer, and a phase comparator calculating a phase difference between a signal output from the Hilbert transformer and a signal output from the delay circuit.

An apparatus for reading from or writing to optical recording media, having a photodetector and a phase detector for detecting a phase difference between output signals of the photodetector. An object of the present invention is to propose an apparatus in which a phase signal which is as correct as possible is generated. A further object of the invention is to specify a method of which a correct track error signal is determined using a phase detection method. According to the invention, the apparatus has an edge sequence detector for detecting the sequence of edges of the output signals, and a signal blocking unit for blocking the output signal of the phase detector. In particular, the output signal of the phase detector is blocked when an impermissible sequence of zero crossings of phase detected signals.

An optical disk according to the present invention includes: a substrate in a disk shape; guide grooves arranged at a pitch p in a radial direction of the substrate, each of the guide grooves being formed so as to extend in a circumferential direction of the substrate; and a pre-pit formed in a space between the guide grooves so as to extend along the guide groove. The optical disk is configured so that an address signal assigned to each location on a signal surface is indicated by the arrangement of the pre-pit in accordance with a predetermined rule. The pre-pit is composed of a pair of pre-pits formed on respective sides of the guide groove. The pair of pre-pits are arranged so as to be displaced in the circumferential direction so that a distance between inner edges of the respective pre-pits in the circumferential direction is smaller than the pitch p of the guide grooves. An optical disk apparatus of the present invention detects light reflected from the optical disk configured as above, calculates a differential phase detection signal, and detects an address signal using the differential phase detection signal. According to this optical disk apparatus, an address signal can be read reliably even at a region where a recording mark is formed so as to lie over the address pre-pit.

The present invention provides an apparatus used for processing the communication signal, wherein the burst packet in a communication signal comprises an access code. The apparatus comprises the following components: a differential phase detector which is used for leading out the differential phase signal that indicates a plurality of differential phases of the first group of the access code in the communication signal; and a frequency offset estimator which is coupled to the differtial phase detector and is used for comparing the differential phase signal and the ideal differential phase signal for calculating the frequency offset value. The method and the apparatus for processing communication signal according to the invention can reduce the interference effect in the packet detection operation and increase the performance of a frequency offset estimating system.

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. The method of arranging the optical pickup includes, where the propagation path of the light beam transmitted through the plate-type beam splitter to the photodetector is an optical path axis, arranging the optical pickup system so as to have the optical path axis tilted with respect to an axis in a tangential direction of the recording medium and have the photodetector placed away from a rotation center of a motor that rotates the recording medium, and selectively optimizing the arrangement of the photodetector to detect a tracking error signal by the differential phase detection method.

Improved phase locked loops are described which handle momentary breaks in an input communication channel. The phase locked loops provide the capability to "hold" the output clock in a communication system at or very near the last output frequency before the loss of input data. Such phase locked loops include a differential phase detector, an electronic selector circuit, and an operational amplifier based loop filter circuit. The electronic selector circuit provides the differential output of the phase detector at a pair of inputs to the operational amplifier. A voltage controlled oscillator is coupled to an output of the operational amplifier and provides an output frequency for the phased locked loop circuit. The electronic selector circuit is operable to control the input to the operational amplifier to hold an output frequency of the voltage controlled oscillator at a substantially constant frequency.

A control circuit for an optical disk drive includes a frequency detector, a phase detector, a low pass filter, a voltage-controlled oscillator (VCO), and a controller. The frequency detector and the phase detector both receive an eight-to-fourteen modulation (EFM) signal and a data phase-locked loop (DPLL) signal. The controller can calculate a target frequency and control the VCO to output the DPLL signal according to the target frequency. During a non-seek mode, the VCO outputs the DPLL signal according to output of the frequency detector, phase detector, and low pass filter. During a seek mode or when spindle speed of the optical disk drive changes, the VCO outputs the DPLL signal according to the target frequency. The controller further outputs charge pump currents for the frequency detector and the phase detector and sets an RF equalizer signal and a differential phase detector (DPD) equalizer signal according to the target frequency.