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Europäisches Patentamt

Absolute position length measurement type encoder | Absolutpositionscodierer vom Längsmessungstyp | Codeur de type mesure de la longueur absolue de la position

IPC Hauptklasse:G01D0005347
Anmelder:Mitutoyo Corporation (0)
20-1, Sakado 1-chome, ; Takatsu-ku, ; Kawasaki, Kanagawa 213-0012, JP
Erfinder:Kusano, Kouhei (0)
c/o Mitutoyo Corporation; 20-1 Sakado 1-chome Takat, Kanagawa 213-8533, JP
Morimoto, Kouji (0)
c/o Mitutoyo Corporation; 20-1, Sakado 1-chome; Takatsu-ku, Kawasaki; Kanagawa 213-8533, JP

Abstract / Hauptanspruch
An absolute position length measurement type encoder includes: a scale (102) which has an ABS pattern (104) based on a pseudorandom code and forms bright and dark patterns by the ABS pattern (104) ; a light-receiving element (112) for receiving the bright and dark patterns; a binarization circuit (124) for dividing a digital signal (SA3) in accordance with a signal (SA1) output from the light-receiving element (112) into a mode (B) having high brightness and a mode (D) having lower brightness, carrying out a binarization process by a threshold value (k) where dispersion (σ' B2, σW2 or σT2) with regard to the two modes is maximized, and decoding the pseudorandom code by the unit of minimum line width (PABS) of the ABS pattern (104) from the binarized values; and a position detection circuit (130) for calculating the absolute position of the scale (102) with respect to the light-receiving element (112) by acquiring the correlation between the decoded pseudorandom code and the design value of the pseudorandom code. Thereby, binarization errors of signals produced by the ABS pattern can be reduced, and highly accurate and stabilized measurement of an absolute position is carried out.


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