Research On The Calibration Of The Space State Of The Axis For Swing Arm Profilometer

With the rapid development of science and technology, the large aspheric optical systems have been more and more widely used in the astronomical observation, space optical and other fields. Compared with the spherical optical systems, the aspheric optical systems are better, which feature simpler structures, larger field of view, as well as better image quality. So the large aspheric optical systems have become the development trends of the optical systems in the current and the future. However, the large aspheric mirrors(especially the convex aspherical mirrors) and the off-axis aspheric mirrors are very difficult to test, which is the technical bottleneck that restricts the development of the aspheric optical system. Aiming at this problem, the Swing Arm Profilometer(SAP) is proposed to perform the high precision measurements. The SAP features simple structure, low cost and large measurement range, which can perform high precision measurement on workshop, and raise the efficiency of test and processing. The SAP realizes the measurements of the different surfaces by adjusting the relationship of the axis of the arm bearing and the axis of the worktable bearing. So the determination of the spatial relationships of the two axes accurately is very important. The focus of this paper is to measure the spatial relationships of the two axes accurately. A four laser trackers calibration method is proposed. The main research contents are as follows,1. The developments of the SAP have been investigated both at domestic and abroad. The working principle of the SAP is introduced. The effect of the calibration error of the two axes are analyzed and discussed. To meet the requirement of the 0.5 micron rms in surface error measurement, the measurement uncertainty of the two axes must be controled within 2".2. The structure and the working principle of the laser tracker are introduced. The single laser tracker calibration of the axis of the swing arm is analyzed in theory. A validation experiment is performed, which shows the single laser tracker measurement method can’t meet the specific measurement task.3. A four laser trackers calibration method is proposed. The four laser trackers measurement principle is introduced, the measurement model is established, the measurement algorithm is studied, the four laser trackers layout scheme is analyzed, the uncertainty of the four laser trackers calibration method is analyzed in theory by using the Monte-Carlo simulation method. The calibration experiments of the swing arm axis are done by using the four laser trackers, the experimental results show that the calibration precision of thefour laser tracker is much better than the single laser tracker, which can meet the demand of practical engineering.4. The four laser tracker calibration method is used to calibrate the SAP and a Ф300 mm flat standard validation experiment is performed. The results of the SAP and the interferometer of the Ф300 mm flat standard show the two measurement results are very close and the residual error maps look the same, which verifies accuracy of the four laser tracker calibration method indirectly.