US 6,285,023 B1Granted

Apparatus for generating origin signal of optical linear scale

AssigneeFutaba Denshi Kogyo K.K.

InventorTakahisa Uehira

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Abstract

In a linear scale, a reference point signal is outputted as a signal which is synchronized with an absolute value. 8 is a a/b phase signal generator forming a two-phase a/b signal of a moving signal by an absolute value which divided the inside of pitch when the a scale moves, 31 is a period counter, 32 is a subtracter, 33 is an up-down counter. An absolute value which divided the scale is preset to an internal counter 38 from a counter 25 at the time of, for example, “on” of a electric source, the counted value is changed by a feedback pulse FB forming a a/b phase output signal when the scale moves, a coincidence pulse Pr is outputted from a count comparator 37 when the internal counter 38 comes to a set value Q within a specific 1 (one) pitch, and a reference pulse Pz showing a position of an origin Z can be obtained synchronously with the absolute value interpolating the inside of pitch by extracting the coincidence pulse Pr at a reference position at which an origin detecting signal Sz is detected.

Claims2

Dependent claims

An apparatus for generating an origin signal of an optical linear scale, comprising:

a main scale provided with a first cut line showing at least an origin position and a second cut line graduated longitudinally at equal intervals;
an index scale provided with a cut line across said first and second cut lines, which is placed movably relative to said main scale;
a photoelectric conversion part for detecting Moire fringe generated by the cut lines between said both scales and for generating a signal having sinusoidal waveform which changes by one period every relative movement by unit length and an origin detecting signal showing a range of the above-mentioned origin position;
and
an absolute interpolation means for outputting an interpolating data interpolating the inside of the above-mentioned unit length by generating an interpolating pulse signal according to a prescribed phase deviation of the above-mentioned signal having sinusoidal waveform,
wherein an origin position signal is generated by a logical product of an interpolated count value showing a specific interpolation position information outputted from the above-mentioned absolute interpolation means and the origin detecting signal showing the above-mentioned origin position.

3 more elements

Dependencies are inferred from the claim text.