It shows that a disadvantag ekists when a crsi is used to measure a step structure in a wavefront , but it is useful to adjust a crsi system with lcslm . 4 . according to the didriction effect of an aperture , the spatial resolution of our crsi was analyzed and the transform function of our crsi was calibrated by using the psd method of a step wavefront . and some factors which are associated with the accuracy of our crsi were analyzed too 四、從光學系統衍射效應的角度分析了本文建立的環路徑向剪切干涉儀的空間分辨率,并利用波前功率譜密度的概念對該干涉儀的空間頻率響應特性進行了標定,分析了限制該干涉儀測量精度的主要因素以及徑向剪切比與測量精度的關系,并指出了該干涉儀的測量范圍,結果顯示該干涉儀基本上可用于準確測量中低頻段的波前畸變。