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A real-time distance measurement data processing platform for multi-axis grating interferometry type optical encoders
Author(s): Xinghui Li; Su Xiao; Qian Zhou; Kai Ni; Xiaohao Wang
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Paper Abstract

Among various nano-scale linear displacement sensors, grating scales have been widely used in industrial fields due to their strong anti-interference ability, cost-effectiveness and compactness. The main development directions of the scale are: high precision, large range, high speed, high dimension and absolute type. Our team has completed the optical layout design of the absolute two-dimensional grating rule, which brings new challenges to the design data acquisition and processing hardware system due to the requirements of multiple dimensions and high speeds. There is no real-time data processing system suitable for absolute two-dimensional scales. This paper presents our latest progress in designing and implementing an absolute two-dimensional grating distance measurement real-time data processing platform. Our platform mainly contains four different functional modules. First, the circuit conditioning module performs I-V conversion and signal amplification and filtering on the weak current signal output from the photodiode. Secondly, an 8- channel high-speed data acquisition module with 14-bit resolution and 80 MSPS maximum sampling rate was designed to convert analog laser pulse signals into digital signals. Third, we have established a real-time data processing module that allows 16 bits of data to be entered in the FPGA to calculate the absolute two-dimensional scale distance. Finally, a data transfer module based on 128MB DDR SDRAM and USB 2.0 was added so that we can easily debug the platform on a PC. The performance of our system is evaluated in real time. The test platform consists of a laser, a twodimensional grating optical path, and our data processing system. The absolute two-dimensional scale has a moving speed of 1m/s, a signal frequency of 10MSPS, a laser emitting signal wavelength of 540nm, and a moving distance of 10-15mm. Experimental results show that our system can output at a rate of 2500 points per second. Measurement results, measurement deviation is less than 50nm.

Paper Details

Date Published: 7 March 2019
PDF: 8 pages
Proc. SPIE 11053, Tenth International Symposium on Precision Engineering Measurements and Instrumentation, 110533Y (7 March 2019); doi: 10.1117/12.2512313
Show Author Affiliations
Xinghui Li, Graduate School at Shenzhen, Tsinghua Univ. (China)
Su Xiao, Graduate School at Shenzhen, Tsinghua Univ. (China)
Qian Zhou, Graduate School at Shenzhen, Tsinghua Univ. (China)
Kai Ni, Graduate School at Shenzhen, Tsinghua Univ. (China)
Xiaohao Wang, Graduate School at Shenzhen, Tsinghua Univ. (China)


Published in SPIE Proceedings Vol. 11053:
Tenth International Symposium on Precision Engineering Measurements and Instrumentation
Jiubin Tan; Jie Lin, Editor(s)

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