US 6,555,809 B2Granted

Incremental rotary encoder

AssigneesPENTAX Corporation, Pentax Precision Co., Ltd.

InventorsKatsuhiko Kenjo, Masami Shirai

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Abstract

An incremental rotary encoder having first and second sensors which each output two sine wave signals having a phase difference of 90 degrees while a rotary member of the incremental rotary encoder rotates. The incremental rotary encoder includes an absolute-zero-index detecting device, provided for the first sensor; at least one binary coding circuit which codes each of the two sine wave signals and the zero index signal into a corresponding binary signal; a holding device for holding the level data of the binary signal of each sine wave signal output from the second sensor when the absolute-zero-index detecting device outputs the zero index signal; and a controller for determining whether the phase of the two sine wave signals output from the second sensor advances or delays with respect to the phase of the two sine wave signals output from the first sensor.

Claims20

Dependent claims

An incremental rotary encoder having a drum, a first sensor and a second sensor, wherein said first sensor and said second sensor each output two sine wave signals having a phase difference of approximately 90 degrees, wherein one of said drum and said first and second sensors is relatively rotatable with respect to the other of said drum and said first and second sensors, wherein said first sensor and said second sensor are positioned so as to be offset from each other by approximately 180 degrees about said drum, said incremental rotary encoder comprising:

an absolute-zero-index detecting device, provided for said first sensor, that outputs a zero index signal each time said first sensor detects an absolute zero index formed on said drum;
a binary coding circuit that codes each of said two sine wave signals and said zero index signal into a corresponding binary signal;
a holding device that holds level data of said binary signal of each of said two sine wave signals output from said second sensor, at a time period when said absolute-zero-index detecting device outputs said zero index signal;
and
a controller that determines whether a phase of said two sine wave signals output by said second sensor is one of advanced and delayed with respect to a phase of said two sine wave signals output by said first sensor.

2 more elements

A surveying instrument, comprising:

a leveling board;
a pedestal coupled to said leveling board to be rotatable about a vertical axis relative to said leveling board;
a collimating telescope coupled to said pedestal to be rotatable about a horizontal axis relative to said pedestal;
a horizontal-angle measuring device that measures an angle of rotation of said pedestal relative to said leveling board;
and
a vertical-angle measuring device that measures an angle of rotation of said collimating telescope relative to said pedestal;
wherein at least one of said horizontal-angle measuring device and said vertical-angle measuring device comprises an incremental rotary encoder having a drum, a first sensor and a second sensor, wherein said first sensor and said second sensor each output two sine wave signals having a phase difference of approximately 90 degrees, wherein one of said drum and said first and second sensors is relatively rotatable with respect to the other of said drum and said first and second sensors, wherein said first sensor and said second sensor are positioned so as to be offset from each other by approximately 180 degrees about said drum, said incremental rotary encoder comprising:
an absolute-zero-index detecting device, provided for said first sensor, that outputs a zero index signal each time said first sensor detects an absolute zero index formed on said drum;
a binary coding circuit that codes each of said two sine wave signals and said zero index signal into a corresponding binary signal;
a holding device that holds level data of said binary signal of each of said two sine wave signals output from said second sensor, at a time period when said absolute-zero-index detecting device outputs said zero index signal;
and
a controller that determines whether a phase of said two sine wave signals output by said second sensor is one of advanced and delayed with respect to a phase of said two sine wave signals output by said first sensor.

9 more elements

Dependencies are inferred from the claim text.