Design of Highly Accurate Linear Carriage Guided by Laser Beam Straight Datum and Its Application for Profile Measurement and Machining

通过基于衍射理论的计算机模拟，证明了在夫琅和费衍射区，当谐振镜角不对准或谐振镜中心与毛细管均不对准时，光束强度大于理想谐振腔强度的1/4时，光束中心轨迹直线度小于1 nm / 1 m。随着谐振腔不对准的增加，QPD的束心跟踪精度下降。然而，使用QPD组合孔径对谐振镜进行高精度对准，表明跟踪精度可能小于1 nm / 1 m。结果表明：在姿态控制下，以QPD中心为最优位置的位移传感器端部安装在直线小车上的运动精度等于激光束直线基准的稳定性。设计并搭建了利用波纹管和真空系统控制波束波动的移动真空波束路，工作距离为1m，提高了波束位置和方向的稳定性。设计并研制了低系数热膨胀外谐振镜定向稳定氦氖激光器。在恒温大气条件下用真空光束路径评价定向稳定性，确定了200秒内激光束的水平方向稳定性为32 nrad，垂直方向稳定性为37 nrad。利用安装在直线架上的位移传感器测量表面轮廓，证实了测量精度等同于激光束直线基准的稳定性。平面由超高精密直线运动机构的两轴交叉组成，以定向稳定激光束为直线基准。提出了以平面为平面基准的高精度平面度测量方法。

By the computer simulation based on diffraction theory, it is proved that if beam intensity with angular misalignment of resonant mirror or misalignment of both center of resonant mirror and capillary tube is more than 1/4 the intensity of ideal resonator at Fraunhofer diffraction region, locus straightness of beam center is less than 1 nm per 1 m.Tracking accuracy of beam center of QPD decline as increase of misalignment of resonator. However, using QPD combined aperture for high accurate alignment of resonant mirror, it is shown that tracking accuracy is possible to be less than 1 nm per 1 m. It is shown that the motional accuracy of the end of displacement sensor mounted, with the optimum place to the center of QPD, on the linear carriage under posture control is equivalent to the stability of the laser beam straight datum.Moving vacuum beam path using a bellows and a vacuum system which controls fluctuation by air flow in the beam path, with working distance of 1 m is designed and built, then improves stability of beam position and direction. Directional stabilized He-Ne laser with outer resonant mirror supported by low coefficient thermal expansion is designed and built. Evaluating directional stability using vacuum beam path at thermostatic atmosphere, it is confirmed that horizontal and vertical directional stability of laser beam are 32 nrad and 37 nrad for 200 second.By measuring surface profile using the displacement sensor mounted on the linear carriage, it is confirmed that the measuring accuracy is equivalent to the stability of the laser beam straight datum. The plane is made from crossed two axes of ultra high precision straight motion mechanism with directional stabilized laser beam as straight datum. Ultra high precision flatness measuring method using the plane as plane datum is proposed.