한국광학회지 (Korean Journal of Optics and Photonics)

  • 제34권3호
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  • Pages.117-123
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  • 2023
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  • 1225-6285(pISSN)
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  • 2287-321X(eISSN)
한국광학회 (Optical Society of Korea)
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고해상도 표면 측정을 위한 회전 프리즘 정합 간섭계

Rotational Prism Stitching Interferometer for High-resolution Surface Testing

  • 송인웅 (한국표준과학연구원 첨단측정장비연구소 우주광학팀) ;
  • 권우성 (한국표준과학연구원 첨단측정장비연구소 우주광학팀) ;
  • 김학용 (한국표준과학연구원 첨단측정장비연구소 우주광학팀) ;
  • 이윤우 (한국표준과학연구원 첨단측정장비연구소 우주광학팀) ;
  • 이종웅 (청주대학교 레이저광정보공학과) ;
  • 양호순 (한국표준과학연구원 첨단측정장비연구소 우주광학팀)
  • In-Ung Song (Space Optics Team, Advanced Instrumentation Institute, Korea Research Institute of Standards and Science) ;
  • Woo-Sung Kwon (Space Optics Team, Advanced Instrumentation Institute, Korea Research Institute of Standards and Science) ;
  • Hagyong Khim (Space Optics Team, Advanced Instrumentation Institute, Korea Research Institute of Standards and Science) ;
  • Yun-Woo Lee (Space Optics Team, Advanced Instrumentation Institute, Korea Research Institute of Standards and Science) ;
  • Jong Ung Lee (Department of Laser and Optical Information Engineering, Cheongju University) ;
  • Ho-Soon Yang (Space Optics Team, Advanced Instrumentation Institute, Korea Research Institute of Standards and Science)
  • 투고 : 2023.03.21
  • 심사 : 2023.05.15
  • 발행 : 2023.06.25
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초록

반사경의 광학면이 넓어질수록 높은 공간 주파수 형상이 광학계의 성능에 큰 영향을 주므로, 대형 반사경 성능 평가에서 이를 측정할 수 있어야 한다. 따라서 높은 주파수의 형상을 샘플링할 수 있는 고해상도 형상 측정 시스템이 필요하다. 본 연구에서는 반사경의 고해상도 형상 측정을 위한 회전 프리즘 정합 간섭계(rotational prism stitching interferometer, RPSI)라는 새로운 방법을 제안한다. RPSI는 기존에 사용되고 있는 상용 간섭계에 빔 확장 렌즈, 이송 거울, 회전 프리즘 등을 추가하여 구성되었으며, 간섭계를 움직이지 않고 원통 좌표계를 기준으로 전체 구경을 아우르는 부분 구경 형상들을 측정한다. 측정된 부분 구경들은 최소자승법을 이용한 부분 구경 정합법을 이용하여 정합되며, 빔확장 렌즈 배율의 제곱만큼 높은 샘플링 밀도로 전체 구경 형상 정보를 복원 가능하다. 3배율을 가지는 RPSI를 이용하여 직경 40 mm의 구면 반사경 형상을 측정하였고, 간섭계 단독으로 측정한 전체 구경 형상과 비교 검증하였다. 약 1 nm RMS의 근소한 차이로 유사한 형상을 잘 복원할 수 있었으며, 간섭계 단독으로 사용한 형상 측정 결과보다 렌즈의 배율의 제곱배만큼 향상된 샘플링 밀도로 형상 측정이 가능함을 확인하였다.

The size of an optical surface can significantly affect the performance of an optical system, and high spatial frequency errors have a greater impact. Therefore, it is crucial to measure the surface figure error with high frequency. To address this, a new method called rotational prism stitching interferometer (RPSI) is proposed in this study. The RPSI is a type of stitching interferometer that enhances spatial resolution, but it differs from conventional stitching interferometers in that it does not require the movement of either the mirror tested or the interferometer itself to obtain sub-aperture interferograms. Instead, the RPSI uses a beam expander and a rotating Dove prism to select particular sub-apertures from the entire aperture. These sub-apertures are then stitched together to obtain a full-aperture result proportional to the square of the beam expander's magnification. The RPSI's effectiveness was demonstrated by measuring a 40 mm diameter spherical mirror using a three-magnification beam expander and comparing the results with those obtained from a commercial interferometer. The RPSI achieved surface testing results with nine times higher sampling density than the interferometer alone, with a small difference of approximately 1 nm RMS.

키워드

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