提出了一种基于空间光程差调制的条纹位置测量方法, 用于恒星干涉仪条纹搜寻和条纹追踪.来自基线两端的两光束合束时, 通过合束器在两光束之间引入一个倾角, 用以实现静态的空间光程差调制.使用成像透镜将静态光程差调制得到的白光干涉条纹成像到CCD探测器上.白光条纹位置的偏移与两光束之间的光程差大小相关, 使用获得的干涉条纹实时计算白光条纹位置, 测量出两束光之间的光程差, 用于延迟线的实时光程差补偿, 从而可以稳定干涉条纹.数值模拟和实验结果表明, 采用该方法获得的最大光程差测量误差为0.159 μm, 小于数值模拟和实验所用宽带光的平均波长0.555 μm, 测量精度满足条纹相干的要求.与时间调制方法相比, 该方法原理和算法简单, 且对于大气扰动更不敏感.

A fringe position measurement method is proposed based on the spatial optical path difference modulation, which is applicable to fringe searching and fringe tracking. When combining the two beams from the two ends of a baseline, a static optical path difference modulation is brought in by a beam combiner introducing tilt angle. An imaging lens is used to image the interferogram onto a CCD detector. The translation of the white-light fringe packet is related to the optical path difference between the two combined beams. The position of interference fringe can be computed with the acquired fringe and used to calculate the path difference. The evaluated optical path difference value is further used to cancel the path difference error by the delay line and to stabilize the fringe. The numerical simulation and experimental results indicate that the maximum experimental measurement error is 0.159 μm, which is smaller than the average wavelength 0.555 μm of the broadband light used in the research, the proposed method can achieve the accuracy that meets the requirement of fringe coherencing . Compared with the previous temporal optical path difference modulation method, the proposed method is simple in principle and algorithm implementation, moreover insensitive to atmospheric turbulence.