The splitting mechanism of zero order diffraction pattern by roof prisms

In order to reduce the adverse effects of the roof prism on the imaging quality of the system, the intensity distribution function in the diffraction pattern which is used to analyze the relationship between the characteristic of the zero order diffraction splitting spot and the structural parameters in one roof prism is obtained by methods of polarization ray tracing and far field diffraction integral. The methods are determined by given the general structure parameters of the roof prism, the prism refractive index and the entering azimuth angle if illuminated with linearly polarized light. Based on that, structure parameters and reflection shift on roof surfaces of the roof prisms are analyzed. The result shows that: (1) within the allowable structure angle, the splitting effect decreases with the increase of the structural angle; (2) at a certain wavelength, the optimum condition to eliminate the splitting phenomenon is that the reflection phase shift of the roof surfaces equal to π.