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: There are provided an information write device and an information read device enabling to generate highly accurate contrast signals. When a main light spot Pc is located at the center of the a groove G, the light spot Pc and sub light spots Psa, Psb are each adapted to radiate a disc DSC such that the sub light spots Psa, Psb radiate positions displaced from the center of the land L. The reflected beams of light from the disc DSC caused by the radiation with the light spots Pc, Psa, Psb are detected to generate push-pull signals each corresponding to the light spots Pc, Psa, Psb, respectively, in accordance with each of the detected signals. Furthermore, a signal to be obtained by amplifying an addition signal, given by adding the push-pull signals each corresponding to the sub light spots Psa, Psb, with a predetermined amplification factor K/n, and a push-pull signal corresponding to the main light spot Pc are added to thereby generate a contrast signal.

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: A light beam is emitted by a light source, and an optical system separates the light beam into a main-portion and a sub-portion. The main-portion of the light beam is guided to an information storage medium. A monitor detector receives the sub-portion of the light beam and outputs a detection signal. A controller controls the output power of the light beam emitted by the light source based on the detection signal. Thus, the light beam of the sub-portion, which is not generally used as a light beam to be irradiated on a storage medium, can be efficiently used, and hence the output power of the light beam from the light source may be accurately controlled.

Abstract: A disc player having a prepit detecting circuit which can correctly detect prepits even if phases or amplitude levels of a plurality of read signals read out from a recording disc are deviated from each other. A phase difference between a first read signal and a second read signal read out by first and second reading elements arranged in two regions divided along the direction of recording tracks of a recording disc is detected. A first phase correction read signal is obtained by adjusting the phase of the first read signal by an amount according to the phase difference. A differential value between the first phase correction read signal and the second read signal is outputted as a prepit detection signal.

Abstract: A light beam is emitted by the light source. The optical system separates the light beam into a main-portion and a sub-portion, and guides the main-portion of the light beam to an information storage medium. The monitor detector receives the sub-portion of the light beam and outputs a detection signal. Then, the controller controls the output power of the light beam emitted by the light source based on the detection signal. Thus, the light beam of the sub-portion, which is not generally used as a light beam to be irradiated on a storage medium, can be efficiently used, and hence the output power of the light beam from the light source may be controlled with high accuracy.

Abstract: An optical pickup apparatus is provided with: a light source (20) for emitting a light beam; an optical system (21, 22, 24, 25, 26, 27), which comprises an optical element (24) having an incident surface (24a), to which an AR (Anti-Reflection) coat is not applied and to which the light beam emitted from the light source is inputted obliquely by a predetermined incident angle, for guiding one portion of the emitted light beam transmitted through the incident surface onto an information record medium (32) and guiding a reflection light of one portion of the emitted light beam reflected from the information record medium, and also reflecting another portion of the emitted light beam by the incident surface; a main light detector (30) for receiving the reflection light from the information record medium guided by the optical system and outputting a main detection signal corresponding to record information recorded on the information record medium; a monitor detector (23) for receiving another portion of the emitt

Abstract: A magnetoresistive effect element 5 is physically configured such that the element width is at least three times as large as the element height. A plurality of domain control layers 11 to 13 are located between the magnetoresistive effect element 5 and a plurality of detecting electrodes 8 to 10 in a state that the domain control layers 11 to 13 are closely formed on the magnetoresistive effect element 5. Each of the domain control layers 11 to 13 applies a unidirectional magnetic field to a region of the magnetoresistive effect element 5 vertically disposed in a guard band of the magnetic recording medium 4, the guard band having no information recorded therein. The unidirectional magnetic field is directed in an orientation of an initial magnetization in a single magnetoresistive effect element, the orientation of which depends on a direction of on an easy axis of the magnetoresistive effect element 5.

Abstract: An information recording/reproducing apparatus capable of correctly reproducing information from a large number of recording tracks without requiring tracking servo. A recording medium is formed with at least one pilot track on which a pilot signal is recorded and a plurality of information data tracks which have the same track width as the pilot track and on which information data is recorded, where the pilot track and the information data tracks are arranged adjacent to each other.

Abstract: A tracking error signal generation device is used for an optical pickup device capable of reproducing and/or recording an information signal on a spiral or coaxial signal track of a disk shaped optical record medium of one type among a plurality of optical record media of different types which track pitches are different from each other. The optical pickup device has a light beam irradiation device for irradiating the optical record medium with three light beams; and light detection devices for receiving a reflection light of each light beam. The tracking error signal generation device is provided with: a first operation device for calculating a first tracking error signal according to the three beams method; a second operation device for calculating a second tracking error signal according to a DPP (Differential Push Pull) method; and a selecting device for selecting one of the first tracking error signal and the second tracking error signal on the basis of an instruction from the external.

Abstract: A reading system of an optical disc has a pregroove having a wobbled inside wall and pits for representing recorded data, and a pair of photodetector elements for detecting a spot of a laser beam reflected on the optical disc. The wobbled inside wall is modulated so as to represent absolute time. A differential amplifier is provided for deriving the difference between outputs of photodetector elements. A gain variable amplifier is provided for adjusting the level of one of the outputs to the level of the other output, so that the difference becomes zero.

Abstract: In the photo-detecting device, the light receiving surface of the light receiving element is divided into four sections A, B, C, D in the direction of tracking. To detect any tracking error, the quantities of received light on these four light receiving sections are used to calculate {(A+B)-(C+D)}-.alpha.{(A-B)+(C-D)}, where .alpha. is an adjustable value such as a variable resistance. Since this provides a true tracking error which does not include a dc offset, it is possible to make a correct adjustment of the tracking.

Abstract: The light receiving element of the photo-detecting device of this invention has its light receiving area formed smaller than the diameter of a beam reflected from an optical information recorded disc. This makes it possible for the tracking error signal to be taken from a central area of the beam spot where the light intensity is high. This minimizes the dc offset caused by misalignment between the objective lens and the beam axis. The light receiving surface of the element is divided into at least four sections along a line at 45 degrees to the direction of tracking. A difference is taken between the light quantities received by two divided light receiving surfaces disposed perpendicular to the tracking direction. This differential signal allows adjustment to be made of an angle between the disc and the photo-detecting device in the direction perpendicular to the tracking direction.

Abstract: The light receiving surface of the light receiving element, which receives reflected light from an information recorded disc, is divided into sections along lines passing through the center of the surface which run parallel to and perpendicular to the direction of tracking and which also run at an angle of 45 degrees to the first two lines. The tracking errors are detected either by a push-pull method or a heterodyne method. The two methods are combined and alternately switched into operation depending on whether information is being written into or read from the information recording disc. The push-pull method uses a pair of opposing, divided light receiving surfaces disposed in the direction of tracking and the heterodyne method uses two pairs of opposing, divided surfaces disposed diagonally or at an angle of 45 degrees to the direction of tracking.

Abstract: A method for performing a reproduction and search operation on a data recording and reproducing device of the helical scan type which includes a pair of recording and reproducing heads mounted on a rotary drum. The method includes the steps of: (a) during the reproduction operation, transporting the tape and rotating the rotary drum such that a relative speed between said tape and the heads is either a first relative speed or a second relative speed which is less than the first relative speed; and (b) during the search operation, transporting the tape at a speed substantially greater than a tape speed used during the reproduction operation and rotating the rotary drum at a speed such that a relative speed between the tape and the heads is equal to the second lower relative speed.

Abstract: An apparatus for recording and reproducing digital signals using a helical scan in which a drum of reduced diameter is employed without changing the tape format. Two heads are mounted on a drum at the same height in opposition to each other with a product of the diameter D of the drum and the wrap-around angle of the tape with respect to the rotary drum being constant while the speed of the drum is increased to a speed N times higher than a predetermined speed. One of the heads is mounted higher than the other by a distance of (1-1/N)P to provide a step, and the other head being is mounted at a position an angle behind the position at which the other head directly opposes the one of the heads, which angle is defined by: ##EQU1## where L is the track length in the tape format used when the rotary drum rotates at the predetermined rotational speed, .THETA. is the track angle, P is the track pitch, and C is a constant dependent on the drum diameter D and the wrap-around angle.