Daytime optical observation has always been an important application in spatial situational awareness. Research has found that interference detection techniques can effectively suppress the influence of the skylight background and improve the detection capability of dim targets. However, it is intuitively believed that the interference detection system only has a small field of view (FOV), which is inconsistent with the experimental results (at least an FOV of 20°). This paper will study the reason why the shearing interference detection system can achieve imaging with a large FOV, provide the theoretical analysis conclusions and the simulation results, and then point out that the FOV of the interference detection system can be greater than 20°. A 97° FOV can form image plane interference.