【作者】 敖磊；

【导师】 谭久彬；

【作者基本信息】 哈尔滨工业大学 ， 仪器科学与技术， 2008， 博士

【摘要】 超精密加工、精密和超精密装备制造和光学制造等技术的迅速发展,对光电自准直仪的测量稳定性提出了更高的要求。在实际应用中,尤其对用于实验室环境下的高精度的激光CCD自准直仪,激光光束角漂移对激光CCD自准直系统测量稳定性的影响更是致命的。课题“基于靶标反馈的自准直光束漂移抑制技术研究”的目的就是针对目前由于激光光束角漂移量引起的激光CCD自准直系统测量稳定性差的问题,探讨研究一种高稳定性的激光CCD自准直光束漂移抑制技术。本课题的技术难点在于激光光束角漂移量产生的实质是激光器自身产生的热漂移、空气折射率变化引起的漂移以及大气随机扰动引起的漂移这三种漂移量的综合作用结果,其随机性和不确定性使其无法用简单的数学模型进行描述,这也是当前激光CCD自准直研究领域中一直未能很好解决的重要原因之一。本文提出一种基于靶标反馈的自准直光束漂移抑制技术,设计并研制了基于靶标反馈的激光CCD自准直测量系统,提出并研制了一种分光式靶标探测器,采用分光式靶标探测器可在获取小角度变化量的同时分离并反馈回与测量光束特性完全相同的角漂移量反馈光束,进而结合闭环反馈控制技术抑制耦合在测量信号中的测量光束角漂移量,可实现高稳定性的激光CCD自准直测量。提出并建立采用透视投影变换技术的基于靶标反馈的激光CCD自准直系统数学模型,确定了系统各组成单元之间的坐标对应关系,并且分别针对理想无漂移、有漂移无反馈和有漂移有反馈控制三种情况,分析和推导了CCD图像传感器和四象限探测器接收的光斑位置、分光式靶标探测器旋转角度和激光光束角漂移量之间的对应关系,为基于靶标反馈的激光CCD自准直测量系统的参数调节及性能分析提供理论依据。为了提高激光CCD自准直系统的图像边缘定位精度,进而得到更高的激光光斑中心定位精度,本文提出一种基于正交傅立叶-梅林矩(OFMM’s)及其偏差补偿的亚像素边缘定位方法,通过将OFMM’s的幅值旋转不变性和更低的径向矩阶数应用于边缘检测,并根据不同阶次的OFMM’s之间的关系得出边缘亚像素位置,并对不同模板大小和实际边缘模型引入的偏差进行分析和补偿,从而达到更高的边缘定位精度,实验结果表明,相对于传统的Zernike矩亚像素边缘定位方法,光斑中心重复定位结果的峰峰值由0.29像素提高至0.13像素,而相对于灰度重心法,光斑中心重复定位结果的峰峰值由0.21像素提高至0.13像素,且光斑中心定位偏差的峰峰值由0.23像素提高到0.19像素。最后,本文对基于靶标反馈的激光CCD自准直测量系统进行性能测试和实验研究,测试和分析了激光光束角漂移的特性,柔性铰链的特性以及控制系统的控制特性;对基于靶标反馈的激光CCD自准直测量系统的稳定性进行了测试,实验结果表明,采用该技术后激光CCD自准直光束稳定性测量结果的峰峰值由0.46″减小到0.15″,最后,对自准直测量系统角漂移量产生的主要因素:激光器自身的热漂移、空气折射率变化以及大气的随机扰动引起的漂移进行了相关的分析。更多还原

【Abstract】 With the development of the manufacturing technology in ultra-precision and micro-mechanical, higher requirements on the measurement stability of opto-electronic autocollimator become more and more stringent. In actual applications, the influences of laser beam shift on the measurement stability of the laser CCD autocollimator with higher accuracy are always fatal especially for the experimental conditions.The subject“study of the key technology for autocollimating beam shift restraining based on target feedback”aims at the measurement stability of laser CCD autocollimating system caused by the laser beam shift. The laser CCD autocollimating beam shift restraining technology to realize high measurement stability is discussed. The technical difficulty of the subject result from the laser beam shift virtually composed by three beam shifts, which are the thermal shift of the laser, the shift caused by the change of air refractive index, and the random shift caused by atmospheric disturbance. The characteristics of randomness and uncertainty of the laser beam shift synthetically composed by the three factors can not be simply mathematical modeled. That is also an important problem which still could not be well resolved in laser CCD autocollimation research.This paper presents a technology for autocollimating beam shift restraining based on target feedback. A laser CCD autocollimating measurement system based on target feedback is proposed, in which a beam-splitting target detector to separate and feedback the laser beam shift with the same characteristics as the measurement beam is developed. The beam shift coupled in the measurement beam could be restrained by real-time closed-loop feedback control, and then the higher stability for laser CCD autocollimating measurement is achieved.A mathematical model of the laser CCD autocollimating measurement system based on target feedback is researched using perspective projection transformation techniques. The relationships among every elements of the system are researched, the relationships among the beam spot location received by CCD and QPD, the rotating angle of the beam-splitting target detector, and the laser beam shift are analyzed. The establishment of the mathematical measuring system model could be used for the parameters adjusting and performance analysis of the laser CCD autocollimating measurement system based on target feedback.In order to improve the edge location accuracy, and then higher center location accuracy of beam spot in laser CCD autocollimating measurement system could be obtained, a new subpixel edge location method based on orthogonal Fourier-Meilin moments (OFMM’s) and error compensation is proposed. The detailed information of the edge is fully extracted based on the rotation invariance and the lower radial orders of OFMM’s in edge detection. Subpixel location of the edge is obtained according to the relationships among different orders of the OFMM’s in vertical directions. Compensation of errors caused by templates with different sizes and the actual edge model are also provided to achieve higher edge location accuracies. Experimental results show that the peak-peak value of the repeated locations of the edge location method proposed in the paper is improved from 0.29 to 0.13 pixels compared to the traditional Zernike moments edge location method, the peak-peak value of the repeated locations is improved from 0.21 to 0.13 pixels and the peak-peak value of the edge location results is improved from 0.23 to 0.19 pixels compared to the gray-level weight center method.Finally, the experiment for the performance of the laser CCD autocollimating measurement system based on target feedback is performed. The performance of the laser beam shift, the flexible hinge, and the characteristics of the control system are tested. The measurement stability of the measuring system is also tested. The experimental results show that the peak-peak value of the stability of the laser CCD autocollimating measurement system is decreased from 0.46" to 0.15". At last, the main factors result in the laser beam shift is analyzed.更多还原