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Proceedings Paper

The in-situ LTP window glass optomechanical analysis
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Paper Abstract

The goal of an in situ Long Trace Profiler (LTP) is to adjust the mirror to 0.1 μrad Root Mean Square (RMS) under thermal load. Here we introduce the measurement configuration for in situ LTP. To avoid lens aberration, the moving optical head keeps the optical paths constant, and the reference beam is used to the correct of the unavoidable air bearing errors. The window glass in this test has a rather high optical quality, with a flatness of 1/150 (RMS) over 120 × 20 mm. The optical quality of the window was specified to be ± 1 μrad slope distortion in an aperture length of 100 mm. The window glass deformation for the air pressure was calculated by the Finite Element Method (FEM) software (ANSYS). The window glass deformation results can be fitting by the Zernike polynomial, and then bring it into the sequential optical ray tracing software (ZEMAX), and evaluating the window glass effect on the LTP measurement results. By this approach, we found that this has a constant error. Thus, the window glass air pressure error can be effectively removed from the measurement result to reveal the real mirror profile. Using the in situ LTP measuring result and the data iteration process, the bendable mirror can control the optical surface locate profile and thereby minimize the thermal distort effect. The slope error will be reduced to 0.1 μrad at the thermal load.

Paper Details

Date Published: 9 September 2019
PDF: 10 pages
Proc. SPIE 11109, Advances in Metrology for X-Ray and EUV Optics VIII, 111090Q (9 September 2019); doi: 10.1117/12.2525560
Show Author Affiliations
Ming-Ying Hsu, National Synchrotron Radiation Research Ctr. (Taiwan)
Gung-Chian Yin, National Synchrotron Radiation Research Ctr. (Taiwan)
Chien-yu Lee, National Synchrotron Radiation Research Ctr. (Taiwan)
Bo-Yi Chen, National Synchrotron Radiation Research Ctr. (Taiwan)
Hok-Sum Fung, National Synchrotron Radiation Research Ctr. (Taiwan)
Shang-Wei Lin, National Synchrotron Radiation Research Ctr. (Taiwan)
Duan-Jen Wang, National Synchrotron Radiation Research Ctr. (Taiwan)
Yu-Shan Huang, National Synchrotron Radiation Research Ctr. (Taiwan)


Published in SPIE Proceedings Vol. 11109:
Advances in Metrology for X-Ray and EUV Optics VIII
Lahsen Assoufid; Haruhiko Ohashi; Anand Asundi, Editor(s)

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