일정높이 주사형 헤테로다인 간섭계를 이용한 정밀측정 방법
Precision method by using the constant height scanning heterodyne interferometer
- 주제(키워드) 간섭계 , 비점수차법 , 포커스오차신호
- 발행기관 서강대학교 일반대학원
- 지도교수 이승엽
- 발행년도 2011
- 학위수여년월 2011. 2
- 학위명 석사
- 학과 및 전공 일반대학원 기계공학과
- 실제URI http://www.dcollection.net/handler/sogang/000000046455
- 저작권 서강대학교의 논문은 저작권 보호를 받습니다.
초록/요약
An interferometer system enables a precise surface measurement with the accuracy of sub-nanometer and the relatively wide detecting range. However, the surface height change between adjacent pixels should be limited to one-quarter of the measurement wavelength, which is usually called “2 π ambiguity”. To solve this 2 π ambiguity problem, an astigmatic method, was proposed by adding a simple device. But the astigmatic method of focus error signal depends on both object lens and surface reflectivity. Therefore a new method is need to measure inhomogeneous surface profiles. In this study, a new scanning interferometer scheme which can overcome 2π ambiguity using a feedback control of astigmatic position sensing scheme and an auto-focusing method. Using the proposed scheme, we are able to simultaneously measure both complex reflection coefficient and step-height of the inhomogeneous sample
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