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Design and development of an optical encoder with sub-micron accuracy using a multiple-tracks analyser grating
Guoyong Ye1, Hongzhong Liu1, Weitao Jiang1
1State Key Laboratory for Manufacturing Systems Engineering, Xi'an Jiaotong University, Xi'an 710049, China.
The Review of Scientific Instruments
|February 3, 2017
Summary
This study presents an optimized optical encoder using generalized grating imaging, achieving high accuracy by minimizing harmonic distortions. The developed encoder demonstrates precise positioning with minimal error over a 150 mm range.
Area of Science:
- Optoelectronics
- Metrology
- Optical Engineering
Background:
- Traditional optical encoders face limitations in signal quality and accuracy due to harmonic distortions.
- Harmonic signals can degrade the performance and reliability of precision measurement systems.
Purpose of the Study:
- To develop an optimized optical encoder with enhanced signal quality and accuracy.
- To suppress specific harmonic distortions in encoder signals using advanced grating and photodiode array designs.
Main Methods:
- Implementation of a generalized grating imaging technique.
- Utilization of a multiple-tracks analyser grating to eliminate second and third harmonic signals.
- Employing a photodiode array with optimized cell width to suppress fifth harmonic signals and ensure signal stability via single-field photoelectric scanning.
Main Results:
- Achieved high-quality encoder signals with approximately ideal Lissajous figures.
- FFT analysis confirmed minimal harmonic distortions: second (<0.3%), third (<0.5%), and fifth (<0.1%).
- Demonstrated exceptional accuracy with a positioning error of ±0.12 μm within a signal period and ±0.2 μm over a 150 mm measuring range.
Conclusions:
- The optimized optical encoder design effectively suppresses harmonic distortions, leading to superior signal quality.
- The proposed methods significantly enhance the accuracy and stability of optical encoders for precision applications.
- The experimental results validate the effectiveness of the generalized grating imaging and optimized photodiode array for high-accuracy position sensing.
