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US 5,970,432 AGranted
Apparatus and method for measuring displacement
AssigneeSony Precision Technology Inc.
InventorsShigeru Ishimoto, Toyohiko Matsuda
Life of this patent
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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.
Claims16
A displacement measuring apparatus comprising:
- a) a reference signal generator for generating a reference signal;
- b) a displacement sensor for generating a displacement signal indicative of a relative displacement of an object to be measured to a reference position at which the reference signal generator generates the reference signal indicating the reference position;
- c) a phase modulated signal generator for generating a phase modulated signal indicating a phase difference between the displacement signal generated by the displacement sensor and the reference signal generated by the reference signal generator, the phase difference representing the displacement of the object to be measured with respect to the reference position;
- d) a subtractor for subtracting a period of the phase modulated signal which is converted into a number of pulses of an interpolation clock from that of the reference signal which is converted into the number of pulses of the interpolation clock so as to output a direction signal indicating a direction to which the object to be measured is displaced and output a magnitude of the displacement signal indicating the magnitude of the displacement and which is converted into the number of pulses of the interpolation clock;
- e) a basic clock generator for generating a basic clock having a predetermined period;
- f) a divider for dividing the period of at least one of either the reference signal or the phase modulated signal which is converted into the number of pulses of the basic clock by the magnitude of the displacement signal which is converted into the number of pulses of the basic clock so as to output a multiplier representing the number of pulses of the basic clock per pulse of the interpolation clock;
- g) a clock pulse generator for generating a clock pulse having a period corresponding to that of the basic clock multiplied by the multiplier outputted by the divider on the basis of the multiplier;
- and
- h) a pulse train converter for receiving the magnitude of the displacement signal from the subtractor and for outputting a pulse train signal whose period is derived on the basis of the clock pulse supplied from the clock pulse generator and the magnitude of the displacement signal.
6 more elements
A method of measuring a displacement of an object to be measured comprising the steps of:
- a) generating a reference signal;
- b) generating a displacement signal indicative of a relative displacement of the object to be measured to a reference position at which the reference signal indicating the reference position is generated;
- c) generating a phase modulated signal indicating a phase difference between the displacement signal and the reference signal generator, the phase difference representing the displacement of the object to be measured with respect to the reference position;
- d) subtracting a period of the phase modulated signal which is converted into a number of pulses of an interpolation clock from that of the phase modulated signal which is converted into the number of pulses of the interpolation clock so as to output a direction signal indicating a direction to which the object to be measured is displaced and output a magnitude of the displacement signal indicating the magnitude of the displacement and which is converted into the number of pulses of the interpolation clock;
- e) generating a basic clock having a predetermined period;
- f) dividing the period of at least one of either the reference signal or the phase modulated signal which is converted into the number of pulses of the basic clock by the magnitude of the displacement signal which is converted into the number of pulses of the basic clock so as to output a multiplier representing the number of pulses of the basic clock per pulse of the interpolation clock;
- g) generating a clock pulse having a period corresponding to that of the basic clock multiplied by the multiplier outputted by the divider on the basis of the outputted multiplier;
- and
- h) receiving the magnitude of the displacement signal derived at the step d) and for outputting a pulse train signal on the basis of the clock pulse generated at the step g).
6 more elements
Dependencies are inferred from the claim text.