Abstract: A displacement detecting apparatus includes an error correcting circuit through which a pair of sine wave signals detected by a detecting head unit are corrected. A signal detecting circuit receives the pair of sine wave signals whose phases are shifted by about 90.degree., and detects a magnitude of one of the two sine wave signal when the other one of the two sine wave signals crosses with a reference voltage level. The error correcting circuit calculates an error correction amount of each sine wave signal according to the detected magnitude of the signal and eliminates the calculated error correction amount from the signals. Therefore, the sine wave signals of position information are accurately corrected in direct-current component, voltage ratio and phase difference.

Abstract: A position detecting apparatus can detect a position with high accuracy even when a relative angle between a magnetic recording medium and a magnetic detecting portion is fluctuated, when an angle of the magnetic recording medium is partly fluctuated or even when an ambient temperature and a temperature of the magnetic detecting portion are fluctuated. The position detecting apparatus includes a magnetic recording medium (1) in which magnetic information is recorded and a magnetic detecting portion (2) movable relative to the magnetic recording medium (1) and which detects the magnetic information recorded on the magnetic recording medium (1). The magnetic detecting portion (2) includes a plurality of, for example, m magnetoresistance effect elements (3) with an artificial grid film structure wherein conductive layers (3a) and magnetic layers (3b) are alternately laminated. The magnetoresistance effect elements (3.sub.1, 3.sub.2, . . . , 3.sub.

Abstract: A video printer for printing a magnetic pattern of a master tape on a slave tape comprises a read head for reading a control signal printed on the slave tape, a phase shift circuit for shifting a phase of the control signal read by the read head, and a write head disposed downstream of the read head with respect to a running direction of the second tape and for rewriting on the second tape the control signal with the phase shifted by the phase shift circuit.

Abstract: A laser Doppler speed measuring apparatus comprises a laser light source, a photodetector, an FM demodulator, and an integrated filter circuit. A selector switch is interposed between the FM demodulator and the integrated filter circuit so as to ensure switching between an output of the FM demodulator and a terminal for directly receiving an external signal.

Abstract: An interpolation device for executing an interpolation of cyclic analog signals includes an analog-digital converter which converts the analog signal to a digital signal. A digital filter removes a high-frequency component of the output digital signal from the analog-digital converter, and the filtered digital signal is interpolated by an interpolation section. Therefore, the deviation of the lower several bits of the digital signal to be inputted to the interpolation section is suppressed so as to prevent the degrading of the accuracy due to such deviations.

Abstract: A position detecting apparatus for a scale measuring system executes a offset correction of the detected three-phase signals A, B and C by using the arithmetic mean (A+B+C)/3 as an offset value. Further, the apparatus executes a gain correction of the offset corrected signals by using a gain which is obtained by the calculation of a square-root of {A.sup.2 +(B-C).sup.2 /3}. Therefore, the accurate measurement is executed by this apparatus even if the gain level is changed at a turn-on of an electric source of this apparatus.

Abstract: A fixed point detecting device comprises a light source, a hologram disposed therebelow and having two portions, and two light receivers for detecting lights diffracted by the two portions of the hologram, wherein an angle of diffraction of light diffracted by one of the two portions of the hologram and an angle of diffraction of light diffracted by another of the two portions of the hologram have opposite signs and the same absolute value and are constant along the axis of measurement, and a difference in luminous intensity is great between positive and negative homogeneous lights diffracted by the two portions of the hologram.

Abstract: A magnetic linear scaling device including a stationary base and a magnetic scale secured to the stationary base. The magnetic scale has a track including a detection area in which magnetic scale data is recorded. A magnetic head is so disposed as to be movable along the magnetic scale in an opposed relation thereto. The magnetic head detects the magnetic scale data recorded in the detection area of the track. A resin tape covers at least the detection area of the track to protect the magnetic scale data from being damaged. The resin tape has a first surface attached to the magnetic scale and a second surface opposed to the magnetic head.

Abstract: A displacement detecting system comprises an optical detector which includes a one-chip optical IC having a laser light source, light receiving elements for generating, in response to laser light reflected by a surface to be measured, a focus error signal indicative of a deviation of a distance between the surface and an objective lens from a focal length thereof, and a prism.

Abstract: In an instrument and method for optically measuring a displacement of a scale which can achieve the noise elimination of returning light to a coherent light source, the scale and optical system are so constructed that an intersecting point of light fluxes radiated from the coherent light source and split into those fluxes by means of a first beam splitter is not present on a transmitting type diffraction grating and the incident lights (d, e) on a reflecting plate and the reflected lights (f, g) from the reflecting plate have no common use of the same light paths.

Abstract: A scale plate arrangement is adapted to be attached to a machine tool for detecting, for example, position and velocity of an object. The scale plate arrangement includes a scale-plate base and a scale plate which has a scale thereon. The scale plate is welded to the scale-plate base. With this, it is not necessary to use an adhesive or a fixing member to attach the scale plate to the scale-plate base. In case that the scale plate has a magnetic scale and that the scale-plate base is made of a magnetic material, the scale-plate base is formed with a recess which is positioned under the magnetic scale. With this, magnetic influence of the scale-plate base on the magnetic scale can be prevented.

Abstract: An interpolation device for a scale arrangement receives sine wave and cosine wave signals indicative of a measuring data from the scale arrangement and calculates a DC offset value, an amplitude coefficient and an amount of a phase drift on the basis of the received signals. The interpolation device outputs a correct angle signal upon removing a DC offset, a gain level error, a gain unbalance and a phase drift from received signals. Therefore, the interpolation device realizes a mechanical structure of the scale arrangement to be simple.

Abstract: A displacement detecting apparatus for detecting a displacement between an object lens thereof and a measured surface in a non-contact manner. The displacement detecting apparatus comprises an object lens for focusing laser beam on the measured surface. A detecting optical system is provided to detect a focus error signal which represents a difference between a distance of the object lens from the measured surface and a focal distance of the object lens, in accordance with a reflected light from the measured surface. An actuator is provided to move the object lens in an optical axis in a manner to cause the object lens distance to coincide with the focal distance, in accordance with an output signal from the detecting optical system. A moving body includes a linear scale or a scale head and movable with the object lens. The linear scale is disposed coaxially with the optical axis and connected to the actuator. A support member is provided to movably support the moving body.

Abstract: A displacement measurement apparatus utilizing an astigmatism, comprises an objective lens, an optical system detecting an offset distance between a relative distance of the objective lens to a measured surface and its focal distance by utilizing a reflection beam from the measured surface, to generate a focus-error signal, an actuator connected to the lens for moving the objective lens in a direction of an optical axis of the lens on the basis of the focus-error signal, so that the relative distance is maintained at the focal distance, and a linear scale and a detecting head cooperative with each other for detecting a displacement of the linear scale to the head. One of the linear scale and the head is integrally connected to the actuator for moving together with the lens and coaxially aligned with the optical axis, and the other is stationary.

Abstract: An apparatus for detecting a relative displacement between a scale and a head is disclosed in which an equilibrium modulated signal derived from at least one detecting head is processed and converted into a DC voltage signal, a level of the DC voltage signal indicating the relative displacement of the scale to the head. At least one sample-and-hold circuit (its sampling time is synchronized with a reference signal, i.e., an excitation signal supplied to the head) or peak/hold circuit and low-pass filter (smoother) is used to provide the DC voltage signal.

Abstract: A splicing tape feeding device is disclosed which is adapted for supplying a splicing tape for joining a magnetic tape to a leader tape. The splicing tape feeding device includes a stationary base member and a movable member displaceable relative to the base member. The base member and the movable member have splicing tape transport paths with a lateral width not less than that of the splicing tape. Parallel flanges are formed on opposite sides of each of the tape transport paths and prevent a lateral displacement of the splicing tape. Engageable mating portions are formed on the base member and the movable member to eliminate a distance in the feeding direction of the splicing tape between the base member and the movable member.

Abstract: A reel holder for use in a tape winding apparatus comprises a cylindrical drum unit which is rotated by the tape winding apparatus. A plurality of lock pins are radially movably mounted in a peripheral portion of the drum unit. Each each lock pin is axially movable between a projected position wherein an outer end thereof is projected outwardly from a cylindrical outer wall of the drum unit and a retracted position wherein the outer end thereof is retracted into the drum unit. First and second buttons are mounted on an axial end of the drum unit. Each button is movable in parallel with the axis of the drum unit between raised and depressed positions with respect to the axial end of the drum unit. A transmission device is installed in the drum unit and operated in such a manner as to move the lock pins to the projected position when the first button is moved to the depressed position and permit the lock pins to return to the retracted position when the second button is moved to the depressed position.

Abstract: A tape winding apparatus, in which a tape drawn from a pancake reel and loaded onto a reel base is wound and accommodated within a cassette, includes a pancake reel exchanging apparatus, wherein at least two pancake reels coaxially disposed with respect to the axial direction of the reel base are loaded onto the reel base. Therefore, a plurality of pancake reels can be loaded onto this tape winding apparatus and the tape winding apparatus can be made comparatively small in size.

Abstract: A position detecting apparatus is comprised of a magnetic scale formed by sequentially disposing magnets at a lattice pitch .lambda., and a magnetic sensor disposed in an opposing relation to the magnetic scale so as to become relatively movable to each other, wherein the magnetic sensor includes a plurality of magnetic sensor elements, each having first and second magnetic reluctance elements, the first and second magnetic reluctance elements are spaced apart from each other by 1/6.lambda. in the direction in which the magnets are disposed and connected in series, and the first and second magnetic reluctance elements are disposed so as not to overlap each other as seen from the direction parallel to the direction in which the magnets are disposed.

Abstract: A hard disc drive is comprised of a casing, a head arm located in the casing and movable in unison with a head, and a diffraction grating mounted on the head arm so as to diffract a light introduced into the casing from the outside of the casing, in which a light diffracted by the diffraction grating is introduced to the outside of the casing. Also, this hard disc drive further comprises an optical system provided outside the casing for receiving the diffracted light, the optical system detecting the arm position, a controller for controlling the arm position, and a servo signal writer for writing a servo signal on the disc on the basis of a detected signal.