现代Michelson恒星干涉仪精度要求的分析

ANALYSIS OF THE TOLERANCE OF A MODERN MICHELSON STELLAR INTERFEROMETER

本文根据现代Michelson恒星干涉仪的工作原理,分析了定天镜、光程补偿器、波前倾斜改正镜等仪器各部分的误差对干涉条纹可见度的影响,并讨论了消除某些仪器误差的办法。

With the theory of the modern Michelson stellar interferometry, we discuss in this paper how the loss of fringe visibility is caused by the instrumental imperfection of different parts of a stellar interferometer. In other words, in order to ensure the accurate measurements of modulus of the source coherence function, a stellar interferometer must meet the tolerance deduced here. The first section of this paper describes the relation between the modulus of the source cohe- rence function and the fringe visibility observed with an interferometer which consists of two apertures of single ro. Section 2 explains the four main factors which cause the loss of fringe vi- sibility. They are the unparallelism (θ″) of wavefronts of the two optical beams when they are combined, the non-zero optical path difference (so) between the two beams, the imperfection (PR) of the surfaces of optical parts involved in the interferometer and the intensity difference (I_1/I_2) between the two beams. Table 1 shows the tolerances corresponding to different losses of fringe visibility (η). The third section and Table 2 illustrate the tolerance of the optical path length compensator, which includes the precision of the path length compensation and the vibra- tions (with different frequencies) of the compensator. The pointing accuracy of siderostats and the spatial stability of the center of a siderostat are discussed in section 4. Fig.2 shows the varia- tion of optical path length caused by the shift of the center of a siderostat. The last section of this paper is the discussion of the possibility of relieving some of the tolerance. The analysis of the tolerance in this paper would serve as a guideline in the design of the prototype of the China Infrared and Optical Interferometry Project.