Encoder for length or angle measuring devices with high accuracy.

摘要

An encoder for measuring devices having a code plate (10) including binary grating patterns arranged in a given regular fashion and forming a first scale, a linear sensor (14) Including photodiode elements (16) arranged with fixed intervals and forming a second scale disposed in parallel with the code plate (10), and processor means (20) for absolute-interpolating one pitch of the first or second scale on the basis of reading data or information (RI) obtained from the linear sensor (14) corresponding to a relative position of the patterns (12) to the elements (16).

When the number of the scale divisions of the first scale within a fixed range is N, the number of the scale divisions of the second scale is N + 1. Accordingly, when the first scale is a main scale, the second scale is a vernier scale. The processor means (20) detects a phase inverting point (X) corresponding to the interpolation point (X) on the basis of the reading data (RI). The processor means (20) performs the absolute Interpolation by detecting the phase inverting point (X).