Abstract
This investigation develops a laser encoder system based on a heterodyne laser interferometer. For eliminating geometric errors, the optical structure of the proposed encoder system was carried out with the internal zero-point method. The designed structure can eliminate the geometric errors, including positioning error, straightness error, squareness error, and Abbe error of the positioning stage. The signal processing system is composed of commercial integrated circuits (ICs). The signal type of the proposed encoding system is a differential signal that is compatible with most motion control systems. The proposed encoder system is embedded in a two-dimensional positioning stage. By the experimental results of the positioning test in the measuring range of 27 mm × 27 mm, with a resolution of 15.8 nm, the maximum values of the positioning error and standard deviation are 12.64 nm and 126.4 nm, respectively, in the positioning experiments. The result shows that the proposed encoder system can fit the positioning requirements of the optoelectronic and semiconductor industries.
Highlights
Nowadays, the semiconductor and optoelectronics industries are some of the most important industries worldwide
It is a well-known method [15,16], by which the positioning error of the X or Y axes can be reduced by the two laser encoders, which are represented by the orange arrows
The contributions of this research are shown as follows: 1. Referring to the references of the Abbe error-free design, this research has proposed a geometric error-reducing design for the heterodyne laser encoder in the two-dimensional stage. This embedded optical, mechanical design can improve the accuracy of the positioning stage
Summary
The semiconductor and optoelectronics industries are some of the most important industries worldwide. In the research field of precision positioning technology, there are many ways to reduce geometric errors. The design of the positioning stage in this reference has three laser interferometers that are aligned in x, y, and z directions This design is based on the Abbe principle, which can reduce the geometric error for the positioning system; this is one of the milestones of precision positioning technology. Much research on precision positioning and measuring machines is based on this design [22,23] These error-reduction technologies are achieved through the optical, mechanical design of the stage and laser encoders. This research focuses on the two-dimensional positioning issue and proposes a laser encoder system for the precision X–Y stage. Proposed heterodyne laser encoder system Previous system based on internal zero-point method [24] Previous system based on external zero-point method [21,22,23] Commercial encoder system of optical grating interferometer
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