# Research on Optical System of Dim Target Simulator Based on Polarization Stray Light Suppression
## 5 Conclusions  
In order to meet the optical simulation requirements of dim space targets, a simulation method of dim space targets based on LCOS splicing display technology and polarization stray light suppression technology is proposed. The mechanism of generating stray light in the optical engine is analyzed. Quarter slide phase compensation is used to reduce dark state light leakage, optimizing the matching of the illumination system and critical incident angle of the spectroscopic film to improve the optical engine stray light suppression ability. At the same time, the collimation optical system with large field of view and high image quality and flat aberration is designed, and the polarization stray light suppression effect verification test and star position simulation error calibration test are set up. The results show that the grayscale contrast of the dim target simulator is 6.96, the non-uniformity of the bright state is only 5.88%, and the simulation error of star position is 9.9\".  
However, it can be seen from the experimental results of the simulated black and white grid that the high contrast between bright and dark regions of the target simulation system after depolarization stray light is reduced in the transition area, but there is a sudden increase in the grayscale of pixels in some regions. Therefore, the research should be further aimed at reducing the transition area and clarifying the abnormal grayscale mechanism.  
Compared with the traditional dynamic target simulation method, the proposed dim target simulation method based on polarized stray light suppression technology  
\begin{table}
\begin{tabular}{c c c} \hline \hline \multirow{2}{*}{**Parameters**} & **Traditional Dynamic Target Simulation** & **Dim Target Simulation Method Based** \\  & **Method with Unpolarized Stray Light** & **on Polarized Stray Light Suppression** \\ \hline \multirow{2}{*}{Grayscale contrast} & 2.51 & 6.96 \\ \hline \multirow{2}{*}{Grayscale non-uniformity} & 33.99\% & 5.88\% \\ \hline \multirow{2}{*}{Simulation error of star position} & 18.99\" & 9.90\" \\ \hline \hline \end{tabular}
\end{table}
Table 4: Comparison of main parameters of the target simulation system before and after depolarization stray light.  
Figure 19: Simulation error results of star position before and after depolarization stray light. (a) Results before depolarizing stray light; (b) results after depolarizing stray light.  
can effectively suppress the polarized stray light in the optical engine, meet the ground calibration requirements of dim target detection system, provide strong technical support for improving the simulation magnitude and simulation accuracy of dim targets, and have far-reaching influence on the development of advanced deep-space detection capabilities.  
Conceptualization, X.L. and S.L.; methodology, X.L., S.L. and J.Z.; software, X.L. and Y.W.; resources, X.L. and S.L.; data curation, X.L. and S.L.; validation, X.L., S.L., J.Z. and Y.W.; formal analysis, investigation, and writing, X.L.; review and supervision, H.L. and Z.W. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the National Natural Science Foundation of China (62105042).  
Not applicable.  
The data presented in this study are available in article.  
The authors declare no conflicts of interest.