Sony Precision Technology Inc.

Toyohiko Matsuda

Shigeru Ishimoto

Masato Tanaka

Katsumi Kitamura

Angle data ranging from 0&deg; to 360&deg; obtained by performing polar conversion with respect to a periodic signal are input to a low pass filter having: a phase accumulator for outputting smoothed angle data; a phase comparator for obtaining a phase error between the angle data and the smoothed angle data; a first amplifier for amplifying the phase error; a second amplifier for further amplifying the phase error; an integrator for integrating the phase error PE amplified by the second amplifier to obtain a velocity error; and an adder for adding the phase error amplified by the first amplifier and the velocity error to determine a control voltage. The phase accumulator controls the frequency of the smoothed angle data so that the phase error is zero based on the control voltage to remove a high frequency component in the angle data.

Position detection apparatus and arithmetic processing unit

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 &minus;Hys<&Dgr;PF<&plus;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<&minus;(Hys&plus;SR) or &Dgr;PF>(Hys&plus;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.

Position detection apparatus

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.

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.

Displacement detecting apparatus

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.

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Kanagawa, Japan

Toyohiko Matsuda