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US 9,851,224 B2Granted
Displacement measuring device and displacement measuring method
AssigneeMitutoyo Corporation
InventorsSatoshi Adachi, Youhei Toku, Toshihiro Hasegawa
Life of this patent
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Abstract
A phase detector includes a sampling signal generator configured to generate a sampling signal at an edge of a scale signal, a counter configured to count up a count value according to a clock pulse every certain time and to output the count value at a timing instructed by the sampling signal, an edge polarity determinator configured to determine whether an edge polarity of the scale signal is a rising edge or a falling edge and to generate an adjustment signal when the polarity of the edge where the sampling signal is generated is a falling edge and an adjuster configured to add a predetermined adjustment amount to the count value output from the counter when receiving the adjustment signal.
Claims4
A displacement measuring device comprising:
- a main scale;
- a detection head provided to be relatively displaceable to the main scale and configured to output a periodic signal having a phase to be changed according to relative displacement to the main scale;
- a demodulator configured to demodulate the periodic signal into a rectangular wave scale signal having phase information at an edge;
- a phase detector configured to detect the phase information of the rectangular wave scale signal at a timing of the edge, wherein
- the phase detector comprises:
- a sampling signal generator configured to generate a sampling signal at the timing of the edge of the rectangular wave scale signal;
- a counter configured to count up a count value according to a clock pulse every certain time and to output the count value at a timing instructed by the sampling signal;
- an edge polarity determinator configured to determine whether a polarity of the edge of the rectangular wave scale signal is a rising edge or a falling edge and to generate an adjustment signal when the edge, from which the sampling signal is generated, is the falling edge;
- and
- an adjuster configured to add a predetermined adjustment amount to the count value output from the counter when receiving the adjustment signal;
- and
- an average calculation executor configured to calculate an average of k number of sampling values, wherein
- the counter synchronizes with a reference signal and is a loop counter in which k/2 periods of the reference signal is a cycle of the count value,
- the sampling signal generator generates the sampling signal successively k times at the timing of the edge of the rectangular wave scale signal after sampling becomes enabled,
- the edge polarity determinator generates the adjustment signal after the sampling becomes enabled and when a first edge of the rectangular wave scale signal is the falling edge, and
- the adjuster adds a value equivalent to 1/k of a cycle of the counter to the count value output from the counter as an adjustment amount, where k is a natural number.
13 more elements
A displacement measuring device comprising:
- a main scale;
- a detection head provided to be relatively displaceable to the main scale and configured to output a periodic signal having a phase to be changed according to relative displacement to the main scale;
- a demodulator configured to demodulate the periodic signal into a rectangular wave scale signal having phase information at an edge;
- a phase detector configured to detect the phase information of the rectangular wave scale signal at a timing of the edge, wherein
- the phase detector comprises:
- a sampling signal generator configured to generate a sampling signal at the timing of the edge of the rectangular wave scale signal;
- a counter configured to count up a count value according to a clock pulse every certain time and to output the count value at a timing instructed by the sampling signal;
- an edge polarity determinator configured to determine whether a polarity of the edge of the rectangular wave scale signal is a rising edge or a falling edge and to generate an adjustment signal when the edge, from which the sampling signal is generated, is the falling edge;
- and
- an adjuster configured to add a predetermined adjustment amount to the count value output from the counter when receiving the adjustment signal;
- and
- an average calculation executor configured to calculate an average of k number of sampling values, wherein
- the counter synchronizes with a reference signal and is a loop counter in which (k+α)/2 periods of the reference signal is a cycle of the count value,
- the sampling signal generator generates the sampling signal successively k times at the timing of the edge of the rectangular wave scale signal after sampling becomes enabled,
- the edge polarity determinator generates the adjustment signal after the sampling becomes enabled and when a first edge of the rectangular wave scale signal is the falling edge, and
- the adjuster adds a value equivalent to 1/(k+α) of a cycle of the counter to the count value output from the counter as an adjustment amount, where k and a are natural numbers.
13 more elements
Dependencies are inferred from the claim text.