Design Of Grating Macro-micro Compound Displacement Measurement System Based On Linear Array CMOS

With the rapid development of the microelectronics industry,the requirements for high-speed and high-precision performance of microelectronics manufacturing equipment are getting higher and higher.How to obtain higher measurement accuracy at high speeds is not only closely related to the future development of the microelectronics industry,but also it is of far-reaching significance to improve my country's comprehensive manufacturing capabilities.Compared with precision measuring instruments such as encoder disks and laser interferometers,grating measuring sensors are widely used in various measurement industries due to their low price,high resolution,compact structure,and high precision.The traditional grating sensor mainly obtains the displacement measurement value based on the counting of the moiré fringe.In order to improve the accuracy of displacement measurement,complex subdivision processing can be used for the moiré fringe,but it is easy to be interfered by external noise and reduce the accuracy;or the grating distance of the grating can be reduced to improve the accuracy,and the high-density grating reticle process can be used Complex,high production environment and technical requirements,difficult to meet the requirements.First of all,in view of the inherent contradiction between speed and accuracy prevailing in incremental grating displacement measurement systems,this paper proposes to use the high line frequency,high resolution and other characteristics of the linear array camera to design an incremental grating macro based on the linear array CMOS image sensor.The micro-composite displacement measurement system replaces the traditional Moiré fringe measurement method.Among them,the high-line frequency feature can not only reduce the image blur problem at high speed,but also eliminate the impact of the vibration of the moving platform;in order to improve the accuracy of the measurement value,this paper proposes a method of vertical and horizontal conversion to increase the system resolution,which is about line the array CMOS image sensor and the grating ruler form a certain angle.Secondly,in the hardware system design process,the optical imaging system is composed of linear array light source,objective lens,adapter,light source controller,line array camera and other hardware,and then the rotation controller platform is built,and matrox image acquisition card is used to meet the requirements.Fast data transmission;in order to reduce the impact of experimental equipment on the accuracy of the system,according to the size and structure of the existing hardware equipment,a mechanical platform and clamping device that are easy to perform three-axis fine-tuning are designed.Then,in the process of designing the software system scheme,the C++ programming language was used to complete the coding of raster image acquisition and macro-micro composite displacement measurement algorithm,and the local adaptive threshold method was used to eliminate the influence of uneven illumination of the raster image.Aiming at the problem that the collected raster images have a lot of noise and stains and scratches,a raster reconstruction algorithm combined with morphological methods is proposed to process them.According to the characteristics of the linear raster image,the software method is used to determine the direction of movement,and then the development of the QT-based human-computer interaction interface is completed,which is convenient for debugging and observation during the experiment.Finally,the experimental parameters on the hardware and software are modified in the calibration process,and comparative experiments with the Renishaw laser measuring instrument as the standard are conducted,to analyze the experimental results and error sources.Experimental results show that under the existing experimental conditions,the measurement system designed in this paper can achieve a displacement measurement accuracy of 2um,a maximum movement speed of 0.9m/s,and a maximum resolution of 0.06? m.The linear CMOS-based grating macro-micro composite displacement measurement method proposed in this paper provides a new research reference method for the field of grating measurement.