Korean Journal of Optics and Photonics (한국광학회지)

Optical Society of Korea (한국광학회)
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Analysis of the Optical Measurement Error Induced by Vibration of the Optical Measurement Tower for Large Mirrors

대구경 반사경 광학측정용 타워의 진동에 의한 광학측정오차 분석

  • Kang, Pilseong (Advanced Instrumentation Institute, Korea Research Institute of Standards and Science) ;
  • Kim, Ohgan (Advanced Instrumentation Institute, Korea Research Institute of Standards and Science) ;
  • Ahn, Hee Kyung (Advanced Instrumentation Institute, Korea Research Institute of Standards and Science) ;
  • Yang, Ho-Soon (Advanced Instrumentation Institute, Korea Research Institute of Standards and Science)
  • 강필성 (한국표준과학연구원 첨단측정장비연구소) ;
  • 김옥관 (한국표준과학연구원 첨단측정장비연구소) ;
  • 안희경 (한국표준과학연구원 첨단측정장비연구소) ;
  • 양호순 (한국표준과학연구원 첨단측정장비연구소)
  • Received : 2017.10.30
  • Accepted : 2017.11.09
  • Published : 2017.12.25
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Abstract

In the present research, the optical measurement error induced by vibration of the optical measurement tower for large mirrors at KRISS (Korea Research Institute of Standards and Science) is investigated. The vibrations of the tower structure, the interferometer, and the null lens are measured while the surface errors of the 600-mm-diameter on-axis aspheric mirror are measuring, under various environmental conditions. The increase of surface error induced by alignment error with respect to vibration is analyzed. As a result, the interferometer and the null lens, which are located on the top of the tower, are highly sensitive to vibration. Additionally, the surface error of the mirror is strongly increased when the vibration directions of the interferometer and the null lens are different. To reduce the alignment error and the surface error induced by vibration, the tower structure should be improved, to be insensitive to low-frequency vibration. Alternatively, optical measuring under stable conditions by vibration monitoring can improve the reliability of the surface error measurement.

본 연구에서는 한국표준과학연구원(KRISS)에 설치된 대구경 반사경용 광학측정타워를 이용한 광학측정 시 타워에 유입되는 진동과 그로 인해 발생하는 광학측정오차에 대한 분석을 수행하였다. 여러 환경조건에 대해 타워구조물, 간섭계, Null lens의 진동측정을 수행하였으며 동시에 직경 600 mm의 축대칭 비구면 반사경의 광학측정을 수행하여 진동과 광학측정오차간의 연관성을 분석하였다. 진동측정 결과 타워의 상단에 위치한 Null lens 및 간섭계가 외부 진동요인에 매우 취약하여 외부 진동유입 시 광학측정오차가 민감하게 증가됨을 확인할 수 있었다. 특히 간섭계와 Null lens의 각 방향 진동이 서로 다르게 발생하는 경우 광학측정오차가 크게 증가하는 것으로 나타났다. 진동에 의한 간섭계, Null lens, 반사경의 정렬오차를 줄이기 위해 타워 구조 시스템이 저주파 진동에 둔감하도록 구조개선이 필요할 것으로 판단되며 진동 모니터링을 통해 간섭계와 Null lens의 진동이 안정화된 시점에 광학측정을 수행하여야 형상 오차 측정값에 대한 신뢰도를 높일 수 있는 것이라 사료된다.

Keywords

References

  1. B. Martin, J. Burge, S. Miller, B. Smith, R. Zehnder, and C. Zhao, "Manufacture of a 1.7 m prototype of the GMT primary mirror segments," Opt. Fabr. Test., Opt. Soc. Am., p. OFWB3 (2016).
  2. J. H. Burge, S. Benjamin, D. Caywood, C. Noble, M. Novak, C. Oh, R. Parks, B. Smith, P. Su, M. Valente, and C. Zhao, "Fabrication and testing of 1.4-m convex off-axis aspheric optical surfaces," Proc. SPIE 7426, 74260LR (2009).
  3. T. L. Zobrist, J. H. Burge, and H. M. Martin. "Accuracy of laser tracker measurements of the GMT 8.4-m off-axis mirror segments," Proc. SPIE 7739, 77390S (2010).
  4. K.-A. Lee, O.-H. Kim, and E.-S. Lee, "Study on fabrication of a large concave mirror surface using a swing-arm type profilometer," J. Korean Soc. Manuf. Process Eng. 7(3), 41-46 (2008).
  5. Y.-G. Kim, H.-G. Rhee, H.-S. Yang, Y.-W. Lee, and J. Lee, "A laser tracker based automatic surface profiling for precision grinding of 1-m scale mirrors," Proc. KSMTE, 287-287 (2015).
  6. J. H. Burge, L. B. Kot, H. M. Martin, R. Zehnder, and C. Zhao, "Design and analysis for interferometric measurements of the GMT primary mirror segments," Proc. SPIE 6273, 62730M (2006).
  7. H.-B. Kim, J.-M. Lim, and H.-S. Yang, "Vibration suppression design on the instrument supporting structure for the optical performance measurement," Proc. KSNVE, 205-208 (2005).
  8. J. Hayes, "Dynamic interferometry handles vibration," Laser Focus World 38(3), 109-116 (2002).
  9. S.-H. Lee, E.-C. Park, K.-J. Youn, S.-K. Lee, E. Yu, K.-W. Min, L. Chung, J.-K. Min, and Y.-C. Kim, "Forced vibration test of a real-scale structure and design of HMD controllers for simulating earthquake response," J. Earthquake Eng. Soc. Korea 10(6), 103-104 (2006). https://doi.org/10.5000/EESK.2006.10.6.103
  10. K.-W. Min, S.-H. Lee, J.-K. Kim, Y.-C. Lee, S.-J. Lee, and H.-H. Choi, "Excitation and system identification of a fullscale five-story structure for the application of viscoelastic dampers," J. Earthquake Eng. Soc. Korea 7(3), 1-7 (2003). https://doi.org/10.5000/EESK.2003.7.3.001