对准系统中调焦机构机械摆动引入误差的补偿

Calibration of error due to mechanical swing of focusing setup in alignment system

为了消减压印对准系统焦平面调整过程中由于机构机械不稳定性产生的对准误差,提出了拟合调整架摆动轨迹来进行软件补偿的方法。通过亚像素模板匹配算法对调焦过程中标记图像的坐标进行定位运算并分析了算法的有效性,结果说明该算法的理论误差<0.1μm。采用该算法计算随调整架摆动的标记坐标,对调整架的摆动轨迹进行了实验标定。分别考察调整架上升和下降时的摆动特性,结果显示,实验具有较好的重复性。以此为基础,建立了调整架的摆动轨迹模型及误差补偿方法,并对模型的预测补偿精度进行了实验研究。结果表明,通过预测调整架摆动轨迹并进行补偿,调焦系统机械不稳定性误差从2.84μm减小到1.29μm,可以满足2μm的总体对准精度要求。

An improved method to fit the side wobble trace of a positioning setup to compensate the software was proposed to reduce the error from the mechanical swing of the focusing setup during focus plane adjustment. The alignment mark was positioned through the sub-pixel correlation template matching algorithm and the validity of the algorithm was investigated, which shows that the resolution of the algorithm is better than 0. 1 um. The positioning algorithm mentioned above was used to calculate the coordinates of the test mark while it moved up and clown along with the focusing positioning setup and then the waving trace was characterized. Experimental results indicate that the mechanical swing trace can offer a good reproducibility, if the ascending and descending of the focusing setup are considered, respectively. Based on the experimental results, the model for the swing trace fitting was established and an error correction method was presented. Finally, experiments were performed to test the calibration accuracy of the model. Obtained results demonstrate that the error from the mechanical instability has been reduced to 1.29 um from 2.84 um, which can meet the overall alignment requirement of 2um.