9 November 2010 Virtual moiré fringe for grating measurement system based on CMOS microscopic imaging
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Moiré fringe is a traditional subdivision technique in precision displacement measurement. In general, use photodiode as a four-segment sensor. In this paper, we'll introduce a new system for grating subdivision of moiré fringe. The system consists of light source, condenser lens, grating, microscope tube, and CMOS image sensors. Different ways with the traditional image acquisition, there is an angle θ between grating stripe and the optical axis of the microscope system. Therefore, the stripe image which output by the CMOS image sensor becomes oblique. With different method of our previous study, a virtual moiré will form by the oblique stripes superimposed with the CMOS image array, which using digital image processing. The same as traditional method, the movement direction of the virtual moiré fringe is vertical with the direction movement of grating in this system. The virtual moiré fringe will move a space with grating period, the magnification has a relationship with the angle θ. Compare with early study, the largest increase for this system is the average effect of grating measurement system will be fully utilized by virtual moiré formed by CMOS image array. For the subdivision technique use the CMOS image array, system resolution will be large increased too. In this paper, the details of system components will be introduced, the magnification relationship of grating period and tilt angle will be discussed. It can be concluded that virtual moiré subdivision system performs better resolution and precision from experiment results.
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Jin Xu, Jin Xu, Wentong Ye, Wentong Ye, Xuxiang Ni, Xuxiang Ni, Xiangqun Cao, Xiangqun Cao, } "Virtual moiré fringe for grating measurement system based on CMOS microscopic imaging", Proc. SPIE 7853, Advanced Sensor Systems and Applications IV, 785325 (9 November 2010); doi: 10.1117/12.869628; https://doi.org/10.1117/12.869628


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