用于自由曲面表面测量的激光差动共焦传感器

Laser differential confocal sensor for freeform surface measurement

针对自由曲面测量问题,构建了一套高精度大量程激光差动共焦传感器。该传感器基于激光差动共焦原理,利用归一化单点定焦模型减小被测表面倾斜角度、反射率的影响,结合非等距分数阶累加预测算法预判焦点位置,实现快速跟踪定焦。将气浮导轨与PZT结合拓展轴向扫描范围。实验表明,该传感器轴向分辨力优于3nm,可测量表面倾斜角度达22°,轴向扫描范围达50mm,差动曲线的过零点标准偏差为5.7nm,有良好的重复性。该传感器为自由曲面的面型轮廓测量提供了一种新的方法。

In order to solve the challenge of freeform surface measurement, a large-range laser differential confocal sensor with high precision was constructed. Based on the principle of laser differential confocal focusing, the sensor uses normalized single-point focusing model to eliminate the influences of the surface reflectivity and tilt of the capsule. A non-equidistant fractional-order accumulation model is used to predict the focus position and achieve fast tracking and focusing. The aerostatic linear guideway and PZT are combined to expand the axial scanning range. The experiment results show that the axial resolution of the sensor is better than 3 nm and the measured surface tilt angle can reach 22°. The axial scanning range can reach 50 mm and the zero-crossing standard deviation of the differential curve is 5.7 nm, which has good repeatability. The sensor provides a new method for measuring the profile of freeform surface.