Article

# Experimental study on subaperture testing with iterative stitching algorithm.

College of Mechatronic Engineering and Automation, National University of Defense Technology, Changsha, Hunan, PR China.

Optics Express (Impact Factor: 3.53). 04/2008; 16(7):4760-5. DOI: 10.1364/OE.16.004760 Source: PubMed

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**ABSTRACT:**Based on the traditional Hindle-Sphere method and Subaperture stitching method, we introduce a measurement method for large convex hyperbolic mirrors. This method uses a small sphere to get the subaperture's surface shape of the convex hyperbolic mirror, and then uses the stitching method to get the full-aperture surface shape. The experimental demonstrations were performed on a convex hyperbolic mirror with our method. The results show that the repeatability of the RMS is 0.002λ (3σ). Compared with the traditional optical compensation method, it is shown that our results are in good agreement with it. Our method can get high-precision full-aperture surface shapes; furthermore, the cost of maintaining it is relatively low and the operation is convenient.Optics and Lasers in Engineering 07/2013; 51(7):856–860. · 1.70 Impact Factor - [Show abstract] [Hide abstract]

**ABSTRACT:**Applying the iterative triangulation stitching algorithm, we provide an experimental demonstration by testing a Φ120mm flat mirror, a Φ1450mm off-axis parabolic mirror and a convex hyperboloid mirror. By comparing the stitching results with the self-examine subaperture, it shows that the reconstruction results are in consistent with that of the subaperture testing. As all the experiments are conducted with a 5-dof adjustment platform with big adjustment errors, it proves that using the above mentioned algorithm, the subaperture stitching can be easily performed without a precise positioning system. In addition, with the algorithm, we accomplish the coordinate unification between the testing and processing that makes it possible to guide the processing by the stitching result.Optics Express 09/2013; 21(19):22628-22644. · 3.53 Impact Factor - [Show abstract] [Hide abstract]

**ABSTRACT:**An aspheric testing system based on subaperture stitching interferometry has been developed. A procedure involving subaperture aberration compensation and radial position scanning was established to resolve discrepancies in the overlapped regions. During the aspheric measuring process, the Fizeau-interferometer axis, the optical axis of the asphere, and the mechanical rotation axis have to be aligned. Due to the tolerance of alignment mechanisms, subaperture interferograms would be contaminated by various amounts of aberrations associated with the rotation angle. These aberrations introduce large inconsistencies between adjacent subapertures in the stitching algorithm. Zernike coefficients of the subapertures in one annulus were examined and each coefficient term was found to be a sinusoidal function of the rotation angle. To eliminate the influence of misalignments, each subaperture was compensated with appropriate amounts of coma and astigmatism to make the resulting Zernike coefficients converge to the mean values of the sinusoidal functions. In addition, the determination of the overlapped regions relies on the precise estimate of the distance between the center of each subaperture and the center of the aspheric optics. This distance was first provided by the encoder and then estimated by position scanning along the radial direction pixel-by-pixel in numerical computations. The means of the standard deviation in the overlapped regions in the simulation and the experimental measurement of an aspheric lens were 0.00004 and 0.06 waves, respectively. This demonstrates the reliability of the subaperture aberration compensation and position scanning process.Proceedings of SPIE - The International Society for Optical Engineering 01/2012; · 0.20 Impact Factor

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