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Proceedings Paper

Optomechanical design of near-null subaperture test system based on counter-rotating CGH plates
Author(s): Yepeng Li; Shanyong Chen; Bing Song; Shengyi Li
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Paper Abstract

In off-axis subapertures of most convex aspheres, astigmatism and coma dominate the aberrations with approximately quadratic and linear increase as the off-axis distance increases. A pair of counter-rotating computer generated hologram (CGH) plates is proposed to generate variable amount of Zernike terms Z4 and Z6, correcting most of the astigmatism and coma for subapertures located at different positions on surfaces of various aspheric shapes. The residual subaperture aberrations are then reduced within the vertical range of measurement of the interferometer, which enables near-null test of aspheres flexibly. The alignment tolerances for the near-null optics are given with optomechanical analysis. Accordingly a novel design for mounting and aligning the CGH plates is proposed which employs three concentric rigid rings. The CGH plate is mounted in the inner ring which is supported by two couples of ball-end screws in connection with the middle ring. The CGH plate along with the inner ring is hence able to be translated in X-axis and tipped by adjusting the screws. Similarly the middle ring is able to be translated in Y-axis and tilted by another two couples of screws orthogonally arranged and connected to the outer ring. This design is featured by the large center-through hole, compact size and capability of four degrees-of-freedom alignment (lateral shift and tip-tilt). It reduces the height measured in the direction of optical axis as much as possible, which is particularly advantageous for near-null test of convex aspheres. The CGH mounts are then mounted on a pair of center-through tables realizing counter-rotation. Alignment of the interferometer, the CGHs, the tables and the test surface is also discussed with a reasonable layout of the whole test system. The interferometer and the near-null optics are translated by a three-axis stage while the test mirror is rotated and tilted by two rotary tables. Experimental results are finally given to show the near-null subaperture test capability of the system for a convex even asphere.

Paper Details

Date Published: 18 September 2014
PDF: 7 pages
Proc. SPIE 9282, 7th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Optical Test and Measurement Technology and Equipment, 92820I (18 September 2014); doi: 10.1117/12.2068330
Show Author Affiliations
Yepeng Li, National Univ. of Defense Technology (China)
Hu’nan Key Lab. of Ultra-Precision Machining Technology (China)
Shanyong Chen, National Univ. of Defense Technology (China)
Hu’nan Key Lab. of Ultra-Precision Machining Technology (China)
Bing Song, National Univ. of Defense Technology (China)
Shengyi Li, National Univ. of Defense Technology (China)
Hu’nan Key Lab. of Ultra-Precision Machining Technology (China)


Published in SPIE Proceedings Vol. 9282:
7th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Optical Test and Measurement Technology and Equipment
Yudong Zhang; Wei Gao, Editor(s)

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