Astigmatism analysis and correction method introduced by an inclined plate in a convergent optical path.

A plate beam splitter can simultaneously increase the transmittances and reflectances of different split spectrum segments. The splitter has been widely used in optical systems. However, when a beam passes through a beam splitter in a convergent optical path, the image quality may be degraded severely because the tilted plate may introduce aberrations such as astigmatism at the on-axis point. The formula for calculating this astigmatism is established. The calculated results are consistent with the simulated results, and the validity of the formula is verified through experiments. A cylindrical lens curvature calculation formula is derived to correct the on-axis astigmatism, which reduces the aberrations introduced by the tilted plate and improves the imaging performance. The imaging characteristics of the off-axis field of view and the reasons for the changes in image quality are analyzed. The F-number range of the converging light path is calculated, which provides a reference for tilted applications of flat-panel optical elements in converging light paths.