Mechatronics 63 (2019) 102274 Contents lists available at ScienceDirect Mechatronics journal homepage: www.elsevier.com/locate/mechatronics Laser encoder system for X-Y positioning stage ✩ Chung-Ping Chang a,∗ , Yi-Chieh Shih b , Syuan-Cheng Chang a , Yung-Cheng Wang c a Department of Mechanical and Energy Engineering, National Chiayi University, Chiayi 600, Taiwan b Department of Mechanical Engineering, National Central University, Taoyuan 320, Taiwan c Department of Mechanical Engineering, National Yunlin University of Science and Technology, Yunlin 640, Taiwan a r t i c l e i n f o Keywords: Geometrical error Laser encoder system Pentaprism beam splitter Precision positioning Positioning stage Interferometer a b s t r a c t In this investigation, a novel opto-mechatronics design of linear Laser encoder system which can eliminate geo- metrical errors of X-Y positioning stage was proposed. The eliminated geometrical errors, which are squareness error, straightness error and Abbe error, can be reduced by this Laser encoder system. Those errors are induced by the mechanical components and assemblies. In this design, a pentaprism beam splitter was employed to divide the laser beam into two encoder axes which are perpendicular to each other. For this arrangement, a real zero point of the positioning stage was set inside the pentaprism beam splitter. Therefore, those specific geometrical errors can be minimized by the proposed system. In this research, the design of the opto-mechatronics structure and its theoretical simulations will be studied. The experimental results which were obtained in the ordinary environment revealed that the resolution of the proposed positioning stage is about 15.8 nm. In addition, the maximum standard deviation of static positioning error is about 50 nm. The Laser encoder system presented in this study is recommended to be used in the precision machinery and semiconductor industries for the precision positioning purpose. 1. Introduction Precision machinery and semiconductor industries are one of the most important industries in worldwide. The positioning system with multidimensional axes and high accuracy is the key to the next gen- eration of those industries. For example, mask aligner, mass transfer of LED, imprint of quantum dots and Laser cutting technology [1–4]. Those technologies are based on the high accuracy positioning stage of sub-micrometer to nanometre scale. For this reason, the positioning technology is one of the most important tasks of the current precision machinery and semiconductor industries. The Laser interferometric technologies have the advantages of large measuring range, noncontact measurement and resolution of nanometer scale. Laser also can trace to the definition of length [5]. Because of those features, Laser interferometers play an important role in the modern length measurement and positioning technology [6]. However, the precision measuring and positioning technology are not only just focusing on the linear motion, but also the straightness and the squareness of the moving axes. Therefore, the multidimensional positioning technology became a key to the next generation of precision positioning technology [7–9]. Currently, the positioning technologies are restricted by the mechan- ical and optical structure. The opto-mechatronics design of the position- ✩ This paper was recommended for publication by Associate Editor “Dr. Lianqing Liu”. ∗ Corresponding author. E-mail address: cpchang@mail.ncyu.edu.tw (C.-P. Chang). ing system provided by G. Jaeger et al., in 2013 [10–12] had been es- tablished. This design is focused on the alignment for six optical axes of the laser interferometers to minimize the Abbe error. The dual-axis nanopositioning stages for analyzing the cross- coupling effect had been proposed by ChaBum Lee et al., in 2017 [13]. In this structure, two optical knife-edge sensor (OKES) based on the interferogram are utilized to determine the displacement of the stage in X and Y axes. In this structure, the voice coil motor is aligned with the movement axis of the stage, and the two sensors are placed perpendicularly with each other to minimize the geometric error. A 2D nanopositioning stage is developed by L.C.Díaz-Pérez et al., in 2017 [14]. In this research, the laser interferometers are employed in the stage as the encoder systems for obtaining the high resolution. By the integrating of the linear motors, Laser interferometers, and control system, the XYRz positioning stage with nanometer resolution and the working distance of 50×50 mm 2 can be realized. The translational displacement algorithm of the grating interferom- eter had been constructed by Weinan Ye et al., in 2018 [15]. The algo- rithm is based on Taylor series expansion and polynomial regression. In the experimental structure, two ZYGO ZMI compact 3-axis high stability plane mirror interferometer are employed to verify the feasibility of the algorithm. By this way, the calculation of the translational displacement https://doi.org/10.1016/j.mechatronics.2019.102274 Received 30 March 2019; Received in revised form 31 July 2019; Accepted 11 September 2019 0957-4158/© 2019 Elsevier Ltd. All rights reserved.