| 摘要 |
PROBLEM TO BE SOLVED: To reduce the binarization error of a signal originating from an ABS pattern and perform stable, high-precision absolute position measurement. SOLUTION: The absolute position length measurement type encoder includes: a scale 102 which is provided with the ABS pattern 104 on the basis of a pseudo random signal and forms a light and dark pattern by the ABS pattern 104; a light receiving element 112 for receiving the light and dark pattern; a binarization circuit 124 which divides a digital signal SA3 following a signal SA1 output from the light receiving element 112 into two modes, or a high-brightness mode B and a low-brightness mode D, to perform binarization processing with a threshold k allowing the dispersion between the two modes (inter-mode dispersion) to be maximized, and decodes the pseudo random signal with a unit of the minimum line width P<SB>ABS</SB>of the ABS pattern 104 from the value subjected to the binarization processing; and a position detection circuit 130 which calculates the absolute position of the scale 102 with respect to the light receiving element 112 by correlating the decoded pseudo random signal with the design value of the pseudo random signal. COPYRIGHT: (C)2010,JPO&INPIT
|
