Abstract: A stable signal is output in which when there is no movement, unstable output change does not occur, and an output change exceeding a predetermined limit does not occur. The variation &Dgr;PH in the output angle signal PH to be output is subjected to hysteresis and through rate limitations with respect to the variation APF in the input angle signal input thereto. When the variation APF in the input signal is in a hysteresis range of −Hys<&Dgr;PF<+Hys, the variation in the output angle signal is output as 0. When the variation &Dgr;PF in the input signal is in a hysteresis range of &Dgr;PF<−(Hys+SR) or &Dgr;PF>(Hys+SR), a through rate limitation is effected to thereby clip the variation in the output angle signal to SR. When the variation &Dgr;PF is in other regions, the output follows the input linearly with the output delayed by the hysteresis quantity.

Abstract: A position detector detects the position of a detector section relative to a record medium having recorded thereon a periodic position signal. The detector section has two detectors that produce first and second detection signals that are polar converted and processed, based on the number of divisions in a quadrant of the periodic position signal.

Abstract: A displacement detecting apparatus includes a scale having a graduation of predetermined pitches, a sensor which is displaceable with respect to the scale and detects a period signal corresponding to the pitch. Interpolating sections interpolate the periodic signal from the sensor by different resolutions. One of the interpolating sections outputs a first interpolation signal of m (positive integer) phases shifted by a phase difference .theta.1, and the other interpolating sections outputs a second interpolation signal of n (positive integer) phases shifted by a phase difference .theta.2.

Abstract: A displacement detecting apparatus outputs a displacement information signal obtained by interpolating a phase modulation. A direction block obtains a direction signal indicative whether the cycle of the phase modulation signal is longer than the cycle of the reference signal. A phase difference block obtains the number of the interpolation clock pulses which number corresponds to a phase difference between the phase modulation signal and the reference signal. An up/down counter counts to an interpolation number upon receiving the direction signal and a pulse train corresponding to the phase difference. The presetting block presets the number of pulses corresponding to the phase difference in the up/down counter. The displacement information block outputs a Glay code converted from continuous 2 bits of the count value of the up/down counter as displacement information.

Abstract: In apparatus and method for measuring a displacement of an object to be measured, a magnitude of the displacement is derived on the basis of a difference in periods of a phase modulated signal and a reference signal, a ratio between the periods of a basic clock and of an interpolation clock which is varied according to the magnitude of the displacement, a clock signal whose period is a multiplication of a period of the basic clock by the ratio as a multiplier, a pulse train signal is created whose number of pulses are given by the magnitude of the displacement and supplied to an A/B phase converter.

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: 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 circuit and method for forming a pulse train output in response to a carry/borrow signal from a calculation of an input pulse train are disclosed in which a plurality of sign-less adders/subtractors and a pulse train output generating circuit are installed. The input pulse train has an interval corresponding to a reference input quantity (0.3517 .mu.m) which is less than a predetermined physical quantity (e.g., 1 .mu.m). Each pulse of the output pulse train has an interval corresponding to the predetermined physical quantity. The adder/subtractors carry out an addition or subtraction of two input numerical values, each numerical value corresponding to the reference unit quantity according to a direction of the input pulse train, whenever one input pulse is received.