| Microelectronics manufacturing equipment is an important field of manufacturing industry,which is related to national interests and national security.As the key technology of microelectronics manufacturing equipment,precision measurement and terminal positioning technology are of great significance for enhancing the comprehensive manufacturing capacity of our country.It is a hot research topic to improve the measurement accuracy and speed of electronic manufacturing equipment and to achieve high resolution measurement at the same time.Grating displacement sensors are widely used in the field of precision measurement because of their simple manufacturing,high precision and low cost.The traditional grating measurement technology relies on electronic circuit to improve the resolution and measurement accuracy by subdividing the Moire frings.So it is easy to be disturbed by external signals.When the equipment moves at high speed,it is easy to lose step,which reduces the measurement accuracy.The research of grating measurement technology started late in China,and grating displacement sensors mostly depend on imports.Therefore,it is urgent to develop and design high-performance grating displacement sensors.Based on the current research progress of the research group,this paper designs a macromicro composite grating displacement measurement system based on virtual instrument.This system uses CMOS image sensor to collect and process grating images instead of subdividing Moire fringes.In this paper,the problem of improving the accuracy,resolution and speed of grating displacement measurement is explored,which lays a foundation for the later development of new grating displacement sensor.Firstly,the theory of displacement measurement with macro-micro composite grating is introduced in detail.It uses software to count the raster pattern after image processing to get macro displacement measurement.And it uses image sensor pixels to calculate the microdisplacement between the grating lines.It lays a theoretical foundation for subsequent research.Secondly,combining with the accuracy and stability requirements of displacement measurement system to build hardware platform.The hardware equipment includes image sensor,optical imaging system,grating ruler,PXI computer,image acquisition card,etc.According to the size and structure design of the equipment used,the mechanical platform is easy to install and adjust,so as to reduce the error caused by the hardware equipment to the measurement.In addition,the proposed macro-micro composite displacement measurement method is programmed on LabVIEW software platform,which uses G language to complete the acquisition,processing,display and displacement calculation of grating image.In order to facilitate on-line measurement,observation and debugging of grating displacement,a humancomputer interface is designed to meet the requirements of the system.Finally,the grating ruler is fixed on the moving platform of Akibis linear motor,and the grating displacement measurement experiment is carried out by using the designed software and hardware.And using the laser interferometer as the standard for comparison,and analysis of measurement results and error sources.Moreover,in order to verify the reliability and stability of the system,the key part of the displacement measurement method of macro-micro composite grating is analyzed on MATLAB.This shows that the system can effectively solve the problems of incomplete grating caused by long-term use and manufacturing process,meanwhile,the advantages of the method described in this paper for grating image processing are also verified.Because of the limitation of experimental conditions such as PXI computer processor and frame frequency of image sensor,the displacement measurement accuracy of this measuring system can reach ±2μm,the maximum velocity 1mm/s and the highest resolution is 0.275μm.The method and research results presented in this paper provide a new idea for the research of grating displacement measurement. |
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