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적외선 광학계용 MTF 측정장치 개발

Development of a MTF Measurement System for an Infrared Optical System

  • 손병호 (과학기술연합대학원 측정과학과) ;
  • 이회윤 (한국표준과학연구원 우주광학센터) ;
  • 송재봉 (한국표준과학연구원 우주광학센터) ;
  • 양호순 (과학기술연합대학원 측정과학과) ;
  • 이윤우 (과학기술연합대학원 측정과학과)
  • Son, Byoung-Ho (Department of Measurement Science, University of Science and Technology) ;
  • Lee, Hoi-Yoon (Center for Space Optics, Korea Research Institute of Standards and Science) ;
  • Song, Jae-Bong (Center for Space Optics, Korea Research Institute of Standards and Science) ;
  • Yang, Ho-Soon (Department of Measurement Science, University of Science and Technology) ;
  • Lee, Yun-Woo (Department of Measurement Science, University of Science and Technology)
  • 투고 : 2015.05.07
  • 심사 : 2015.06.02
  • 발행 : 2015.06.25

초록

본 논문에서는 적외선 파장대에서 렌즈의 변조전달함수(MTF)를 칼날 주사방식으로 측정하는 적외선 MTF 측정장치를 구성하고 평가하였다. 측정장치는 물체부, 평행광을 만들어주는 시준부, 형성된 상을 분석하는 분석부로 나뉜다. 광원으로는 텅스텐 필라멘트 광원을 사용하였으며 중적외선 영상을 검출하기 위해 MCT를 사용하였다. 이 장치를 사용하여 ZnSe 재질의 f 수가 5인 표준렌즈의 MTF를 중적외선 파장대인 $3{\sim}5{\mu}m$에서 측정하고 Zemax 프로그램을 통해 계산한 이론값과 측정값 차이를 비교하여 차단주파수(Cut-off frequency)인 50 1/mm까지 전구간에서 ${\pm}0.035$이내임을 확인하였다. 또한 측정값의 신뢰도를 확인하기 위한 A형 측정불확도를 계산한 결과 MTF의 대표 공간 주파수인 20 1/mm에서 0.002으로 동일한 조건 하에서 측정 시 측정값의 변화가 거의 없음을 알 수 있었다.

In this paper, we developed a MTF (Modulation Transfer Function) measurement system using a knife-edge scanning method for infrared optics. It consists of an objective part to generate the target image, a collimator to make the beam parallel, and a detector to analyze the image. We used a tungsten filament as the light source and MCT (Mercury Cadmium Telluride) to detect the mid-infrared(wavelength $3-5{\mu}m$) image. We measured the MTF of a standard lens (f=5, material ZnSe) to test this instrument and compared the result to the theoretical value calculated using the ZEMAX commercial software. It was found that the difference was within ${\pm}0.035$ at the cut-off frequency (50 1/mm). Also, we calculated the A-type measurement uncertainty to check the reliability of the measurement. The result showed only 0.002 at 20 1/mm in spatial frequency, which means very little variation in the MTF measurement under the same conditions.

키워드

참고문헌

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