In-situ measurement is an ideal method to improve the precision and efficiency of manufacturing. This paper developed an in-situ subaperture stitching interferometric measuring system for large plano optics in the workshop environment. It can realize high precision and considerable repeatability. The principle of in-situ subaperture stitching measurement was introduced briefly. A validation test has been presented to verify that the in-situ measuring can be realized with the developed system.
High precision optical components with large numerical aperture are widely used in industrial products. The stitching interferometry system was designed to measure high-numerical-aperture sphericity and extended the measurement range of interferometry. Firstly, sub-aperture stitching model and experimental system were analyzed. Adjustment mechanism with seven degrees of freedom was built to keep spherical surface in the null position. Then, optical path difference caused by adjustment errors was described by mathematical model. The misalignment aberrations in measurement result were removed after fitted by the Zernike polynomial and the accurate surface shape of single aperture is gained. Finally, a high-numerical-aperture sphericity was measured by the error homogenization algorithm. The PV and RMS are consistent with the results of full aperture testing.
Stitching interferometry is an effective method to extend the measurement range of commercial interferometer. It has been applied in the laboratorial environment, but rarely in workshop. In order to improve the testing efficiency in workshop, stitching interferometry could be combined with machine tool and implement in-situ testing. A dynamic stitching interferometer system is established in this paper, which contains dynamic interferometry, precision motion control and advanced stitching algorithm. This system has been prepared for the in-situ testing of large plano optics. One example optical flat with size 200mm×300mm was used to verify the feasibility and accuracy of this system. Many repetitive experiments have been proved the well reliability of the system and method.
The systemic error is the main error sauce in sub-aperture stitching calculation. In this paper, a systemic error calibration method is proposed based on pseudo shearing. This method is suitable in dynamic stitching interferometry for large optical plane. The feasibility is vibrated by some simulations and experiments.
Accurate and efficient measurement method is necessary to improve the testing efficiency for large optical plane. In this paper, a system is proposed for testing large optical plane in the workshop which combined dynamic interferometry with stitching algorithm. The feasibility is vibrated by an optical flat with 200mm×300mm.
Phase shifting interferometry is commonly used in precision optical surface measurement, but which possesses some limitation because of the sensitivity to environment. Therefore, it is hardly used in optical testing in the workshop environment. Thus, the instantaneous interferometry is a good choice because of the insensitive to vibration. This paper will describe an instantaneous interferometry utilizing spatial carrier and Fourier transform, and discuss the accuracy of the interferometer for optical testing when phase-shifting interferometry is unable to realize the precision measurement. With a lot of experiments, some problems were analyzed, including the relationships between the measurement accuracy and systematic error, vibration, temperature, the test surface cleanliness and so on. The discussed work of error restraint can provide a reference for the instantaneous interferometry applications.