US 5,294,793 AGranted

System for measuring lengths or angles with a high-velocity movable scanning unit

AssigneeRSF-Elektronik Gesellschaft m.b.H.

InventorsMax Schwaiger, Rieder Heinz

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Abstract

A system for measuring lengths or angles comprises a scale member provided with absolutely coded scale elements and incremental scale elements, a movable scanning unit generating position-dependent signals in response to the reading of the scale elements, and an evaluating unit for determining the absolute position of the scanning unit relative to the scale member in response to the position-dependent signals. The coded scale elements consist of different code words arranged according to a serial code and are read by a multiline detector which, in any position of the scanning unit relative to the scale member, reads at least an entire code word. The evaluating unit is adapted to detect the position of the beginning of the detected code word relative to the detector and to read each code word so as to determine the instantaneous absolute position in coarse steps and is also adapted to detect the position-dependent signals generated in response to the scanning of the incremental scale elements and to coordinate them with the signals from said detector for a determination of the instantaneous absolute position in fine steps.

Claims13

Dependent claims

A system for measuring lengths and angles, which comprises

(a) a scale member provided with
(1) coded scale segments successively spaced apart in a scanning direction, the coded scale segments consisting of different serially coded code words, and
(2) incremental scale segments,
(b) a scanning unit mounted for movement relative to the scale member in the scanning direction and generating measuring signals responsive to reading respective ones of the scale segments in any position of the scanning unit relative to the scale member, the scanning unit comprising
(1) multiline detector means reading at least one entire one of said code words and
(2) means for reading the incremental scale segments, and
(c) an evaluating unit determining an absolute position of the scanning unit relative to the scale member in response to the measuring signals, the evaluating unit comprising
(1) means operative for detecting the absolute position in coarse steps by detecting the position of the beginning of the read code word relative to the detector means and the subsequent reading of the code word, and in fine steps by detecting the measuring signals generated by the means for reading the incremental scale segments,
(2) means for controlling the absolute position detecting means to operate only when the scanning unit movement proceeds at less than a predetermined velocity, and
(3) means for processing only the measuring signals generated by the means for reading the incremental scale segments after the absolute position has been detected.

7 more elements

Dependencies are inferred from the claim text.