利用CMOS相机拍摄双棱镜干涉图像，经过图像处理得到干涉光强分布.发现干涉条纹的包络在中央区域存在有规律的起伏，两侧则存在迅速的衰减，明显有别于经典的双缝干涉图样.为解释这个现象，本文考虑了光在双棱镜脊线附近的直边衍射，并利用MATLAB仿真复现了实验观察到的光强分布特征.在此基础上分析了干涉条纹间距的变化规律，条纹数量和可见度与狭缝宽度、双棱镜位置的关系，结论与实验结果符合较好.

The interference pattern of Fresnels biprism is recorded by a CMOS camera and converted to intensity distribution curve. It is found that the envelope of the interference fringes fluctuates regularly in the central region and decays rapidly on both sides, two features cannot be observed in the classic double-slit interference pattern. To explain this phenomenon, a simple model is proposed that take the straight-edge diffraction at the ridge of the biprism into consideration. By MATLAB simulation, light intensity distribution matching the observed characteristics is obtained. The model also implies that the spacing between interference fringes gradually narrows in the diffraction regions on both sides. Moreover, the relationship between the number and visibility of interference fringes in the central region with the slit width and the position of the biprism is studied. All the results are in good agreement with the experiment measurements.