Scientists from the Changchun Institute of Optics, Fine Mechanics and Physics, affiliated with the Chinese Academy of Sciences, have successfully developed a new automatic compensation system that significantly reduces eccentricity errors in optical encoders, a breakthrough that promises to enhance measurement accuracy in industrial applications. This achievement, published in the renowned journal Review of Scientific Instruments.

The study, which focused on addressing a common source of error in high-precision measurement devices, employed innovative techniques to minimize the impact of eccentricity - a condition where the center of rotation of an encoder disk deviates from its geometric center. This misalignment can lead to decreased measurement accuracy, affecting the performance of systems that rely on encoders for precise positioning and control.

To tackle this issue, the research team designed a series of radial code paths around the perimeter of the encoder disk. These paths, combined with the moiré fringe technique, enabled the conversion of mechanical angle information into a corresponding digital code. This approach not only facilitated the detection and quantification of eccentricity errors but also provided a means for their automatic compensation.The experimental process involved the use of four approximate sinusoidal signals (J0, J90, J180, J270) output by the reading head. These signals were processed through a differential amplifier to obtain J-SIN and J-COS signals, which were then utilized to calculate radial displacement values. By measuring the eccentricity of the encoder disk and establishing an eccentricity error compensation table, the system could effectively compensate for these errors.

The results of the study were impressive. The peak eccentricity error, which was initially measured at 33.0 arcseconds, was significantly reduced after applying the compensation algorithm. Specifically, the peak error dropped from 27.9 arcseconds to just 3.6 arcseconds, while the mean square error decreased from 21.25 arcseconds to 3.66 arcseconds. This substantial improvement in measurement accuracy was verified using a combination of an autocollimator and a regular heptadecagon as angular references.

The practical implications of this research are profound. Encoders are widely used in industrial measurement and control systems, and any improvement in their accuracy has a direct impact on the stability and reliability of these systems. The new automatic compensation system not only enhances the performance of existing encoders but also paves the way for further advancements in encoder technology.

Looking ahead, the application prospects of this algorithm are vast. It can be adapted to different types of encoders, potentially requiring distinct compensation methods, and could even find use in other precision measurement devices. The research team's innovative approach to reducing eccentricity errors represents a significant step forward in the field of industrial metrology.