F-Theta自由曲面透镜的精密与镜面磨削

Precision and Mirror Grinding of F-Theta Freeform Surface Lens

针对光学玻璃的F-Theta自由曲面透镜加工困难等问题,提出将金刚石砂轮的椭圆环面代替圆环面,进行F-Theta自由曲面磨削加工,研究形状误差的补偿磨削方法和光学玻璃的镜面磨削工艺。根据F-Theta透镜的自由曲面建立砂轮与工件相切的刀具轨迹法向算法。采用#46粗金刚石砂轮修整成椭圆环面,提出自由曲面磨削的法向误差补偿加工模式。最后,采用#3000超细金刚石砂轮的椭圆环面进行轴向磨削试验。试验结果表明:传统的垂直误差补偿磨削可减小面形误差45.9%及其PV值11.6%;而新提出的法向误差补偿磨削可减小面形误差47.9%及其PV值41.5%。此外,超细砂轮磨削可使得自由曲面的粗糙度达到28 nm,其镜面磨削工艺有别于较粗砂轮磨削工艺。因此,椭圆环面砂轮的法向补偿磨削是提高自由曲面加工精度的有效方法,而且,无需研磨抛光就可以实现光学玻璃的自由曲面镜面磨削。

Due to the processing difficulties of optical glass F-Theta freeform surface lens, the form error compensation and the mirror grinding processes of freeform surface using an elliptical grinding wheel instead of the arc one are proposed. The F-Theta freeform surface lens is designed by equation, and a normal algorithm model for planning tool paths of freeform grinding is proposed. Second, the form error compensation is employed to grinding F-Theta freeform surface lens with an elliptical toms-shaped #46 diamond grinding wheel, which includes the vertical from error and normal form error compensation. An elliptical toms-shaped #3000 diamond grinding wheel is employed to grind F-Theta freeform surface lens to study the mirror grinding process. Experimental results show that the vertical form errors Ey and PV of F-Theta freeform surface lens are decreased by 45.9% and 11.6% after traditional vertical form errors compensation, respectively; The normal form errors En and PV of F-Theta freeform surface lens are decreased by 47.9% and 41.5% after the new proposed normal form error compensation, respectively; Besides, The roughness of F-Them freeform surface lens ground by #3000 diamond grinding wheel is 28 nm, and its mirror grinding process is different from the coarse grinding process. It is confirmed that normal form error compensation may be an efficient method for precision grinding of freeform surface. In addition, the #3000 elliptical toms-shaped diamond grinding wheel can fabricate mirror optical glass freeform surface lens without polishing.