Linear Optical Encoder System With Sinusoidal Signal Distortion Below $-$60 dB

This paper describes a high-precision linear optical scanner, combining an averaged optical sensor array with appropriate 10-¿m graduated scales on a measurement-fixed plate and a Vernier sliced parallel scale on a reading plate, where the total distortion of the generated quadrature sinusoidal signals below -60 dB was achieved by distributing and mismatching optical edges over a number of sine-wave periods within a number of Vernier-scaled periods. The reading plate, which is positioned along the optical array, has a unit division smaller than those on a fixed scale, permitting a far more precise positioned optically generated sine-wave current. Position-like averaging of four generated signals was distributed over an optoarray and a reading scale. Optoedge redistribution over a sliced Vernier's period leads to harmonic distortion reduction, of which the third and all odd spectral components were almost removed. The distortion-reduction background with the prototype is presented. A good match was found between the mathematically analyzed optical scanner and the prototype measurement, where comparable measurements were performed on the optical head, having redistributed and fixed-positioned optoedges.

I. Introduction

Accurate measurement of displacement is of prime importance in any computer-controlled machine [1]. The need to manufacture “something” requires the ability to move “something” with a very high level of accuracy. To be able to do so, accurate position sensors, which are also called position encoders, are needed [2]–[5].