相位提取的精度直接影响相移干涉测量的精度。在变频相移干涉测量中，相移量由干涉腔长和波长变化量决定，必须对测试系统进行相位标定，但常因相位标定不精确而引入相移误差，影响相位提取的精度。运用一种基于迭代的相位求解算法，该算法无需对测试系统进行相位标定，可以在被测相位和相移量均未知的情况下，通过交替迭代法求解出被测相位。通过仿真比较了传统四步相移和基于迭代的相位求解算法的相位提取精度，结果表明，基于迭代的相位求解算法的相位提取精度优于传统四步相移算法的精度。

Phase extraction precision directly affects the accuracy of phase-shift interferometry. In the wavelength tuning interferometry, a phase calibration is necessary for the test system, because phase shift is determined by interference cavity length and wavelength variation. But an accurate phase calibration is not easy to achieve. The phase shift error can be caused by an inaccurate calibration, which can decrease the phase extraction precision. A phase extraction algorithm based on iteration is proposed. This iteration algorithm does not need to calibrate the phase of the test system, and it can obtain the testing phase and phase shifts through alternate iteration method under the condition that the testing phase and phase shift are unknown. A series of simulations are done to compare the phase extraction accuracy, and the results suggest that the phase extraction accuracy of the proposed algorithm is quite better than that of the traditional four-step phase shift algorithm.