基于亚波长光纤点衍射干涉技术的三维绝对位移无导轨测量方法研究

The high-precision measurement of absolute three-dimensional distance is indispensable to precise manufacturing field. To meet the need of in-situ three-dimensional absolute distance measurement, this project presents a high-precision method for non-guide three-dimensional absolute distance measurement, which is based on the sub-wavelength-aperture fiber point-diffraction interferometry. The important characteristics of this project are those measurement precision is determined by the point-diffracted precise spherical wavefront, and also the divergence of spherical wavefront is used to realize non-guide three-dimensional measurement.The sub-wavelength-aperture fiber is used as point-diffraction source to get precise and high-energy spherical wavefront within high aperture angle range,by which the conflict between point-diffraction wave angle and energy can be avoided. The precise spherical wavefront used as reference standard is obtained from point diffraction method, and is applied to generate the interference field containing information about the three-dimensional absolute distance under test. With the demodulated phase from interference field, we are capable of reconstructing three-dimensional absolute distance with numerical iterative reconstruction technique. Also, simulation model based on the Finite Difference Time Domain method is established to analyze the point-diffracted wavefront, and it can be applied to guide the paramter design for the point-diffraction source and system development, as well as error analysis. This study will reach the measurement precision better than the level of micrometer in the meter-order measuring range. This novel measurement technology is expected to be widely used in the scientific research and production of the precision manufacturing and measurement field, etc.

三维绝对位移高精度无导轨测量是精密加工制造领域不可或缺的技术手段。本项目提出了基于亚波长孔径光纤点衍射干涉技术的高精度三维绝对位移无导轨测量方法，其特点是以来高精度点衍射球面波前基准来保证测量精度，同时利用球面波前发散性来实现三维方向无导轨测量。为获得大孔径角范围的高精度、高光能量点衍射波前，提出了一种基于单模光纤的亚波长孔径光纤点衍射源，以解决点衍射波前孔径角与光能量之间的矛盾问题。利用点衍射方法获取高精度球面波前作为测量基准并产生含有三维位移信息的干涉场，并根据建立的三维绝对位移重构模型，采用解数值迭代重构算法重构出三维绝对位移信息。同时根据时域有限差分法建立点衍射波前分析模型，用于指导点衍射源与测量系统结构参数设计以及误差分析等。本研究将可对米量级绝对位移范围实现优于微米级测量精度，有望广泛应用于精密加工与测量等领域科研生产中。

三维绝对位移的高精度无导轨测量是精密加工制造领域不可或缺的技术手段。本项目提出了基于亚波长光纤孔径点衍射干涉技术的高精度三维绝对位移无导轨测量方法，其特点是以高精度点衍射球面波前基准来保证测量精度，同时利用球面波前发散性来实现三维方向的无导轨测量。利用点衍射方法获取高精度球面波前作为测量基准并产生含有三维位移信息的干涉场，并根据建立的三维绝对位移重构模型，采用数值迭代优化重构算法得到待测的三维绝对位移。为获得大孔径角范围的高精度、高光能量点衍射球面波前，提出了一种基于单模光纤的亚波长光纤点衍射源，以解决点衍射波前孔径角与光能量之间的矛盾问题。根据时域有限差分方法的矢量衍射理论，对亚波长孔径光纤点衍射球面波前质量进行精确仿真及结构参数优化；同时基于双点衍射波前横向剪切法对亚波长光纤点衍射球面波前基准进行实验标定，提出了适用于大数值孔径点衍射波前的结构误差高精度校正方法以及基于差分泽尼克多项式的点衍射波前重建方法。实际得到的点衍射光斑的孔径全角以及光强透过率分别达到了20°和4.65%，所获得的波前球面精度RMS值优于2×10^(-4)λ。针对实际测量中可靠性、时效性和高精度要求，提出了基于快速搜索粒子群算法的点衍射干涉绝对位移测量方法。所提出的快速搜索粒子群算法针对测量中大量像素点数据的高效处理需要，在三维绝对位移迭代重构过程中采取非线性增加样本点数量的搜索方法，进而在保证测量精度的同时，极大提高了测量效率。利用本研究提出的三维绝对位移测量系统进行实际测量，与三坐标测量机进行比较，结果表明本系统的实际测量精度可达到微米量级。本研究成果可提供一种新型的三维无导轨测量手段，并有望在精密加工与测量等领域科研生产中有着广泛的应用前景。