A high accuracy method for rapid measurement of resulted code pattern radial runout of rotary optical encoder disc

Abstract

Optical rotary encoders are generally known as rotational angle measuring devices with high accuracy, resolution and reliability. One of important sources of error in these encoders is their disc code pattern radial runout. Usually, for high accuracy measurements in the range of ±1 arc sec to ±5 arc sec, the code pattern radial runout resulting from bearing or during installation must be significantly less than 1μm. In this paper, an instrument is purposed for installation of encoded disc that can rapidly measure radial runout of code pattern both during installation and after temporary installation of encoded disc with high accuracy and reliability. Systematic characteristics of this instrument are proven through mathematical equations. Accuracy of determination equations of this measuring method in various setup are evaluated and by analyzing its results, performance characteristics of the proposed instrument are extracted. The purposed instrument can communicate data with a PC, so avoids need to microscope as used in conventional assembly of encoder disc method and also may be used for automatic assemble or monitoring of assembly process of encoded disc. © 2011 Springer-Verlag Berlin Heidelberg.