基于光栅的贴片机对准系统的精度标定

摘要

贴片机对准系统的精度标定是视觉定位的关键环节,直接影响贴片精度与贴片质量.为提高对准系统标定精度,提出了基于光栅的精度标定方法.将光栅图像灰度值之和形成一组周期固定的准正弦信号,通过像元平移把图像条纹灰度值变为李萨如图.对李萨如图及其数据进行分析与处理,直接计算出光学系统的分辨率,从而实现光学系统的精度标定.采用上述方法得到了与理论计算比较吻合的贴片机对准系统精度标定结果,并且利用标准大刻尺进行了标定验证实验.获取了标准大刻尺的图像,通过图像处理计算出刻线间的像素坐标差,将像素坐标差值与成像系统分辨率相乘计算出代表实测的刻线间距.对实验数据的误差分析表明,这种标定方法精度高,偏差＜0.2 μm,满足贴片机的对准精度要求.%Accuracy calibration is a key of the vision alignment system of a high-precision chip mounter,which affects the precision and quality of the chip mounting greatly.For improving the calibration accuracy of the alignment system,this paper presents a new calibration method based on a grating.With proposed method,a group of data similar to quasi-sinusoid signals is abtained by calculating the sum of gray-value of pixels in each column.Then,these calculated data are elaborately converted into a Lissajous figure by pixel translation.The size mapping coefficient between the grating groove and their image pixels of the optical alignment system is calculated to realize the accurate calibration,obtained calibration results indicate that it is coincident with the theoretical calculation results well.A big standard ruler is used to verify the calibration experiment,the error analysis on the experimental data shows that the accuracy error by proposed method is less than 0.2 μn,which can meet the precision needs of vision alignment systems of automatic chip mounters.