# Improvements of Computational Ghost Imaging by Using Sequenced Speckle
## 4 Conclusions  
In this study, we demonstrated the advantages of using sequenced random speckle patterns with varying speckle sizes in DMD-based CGI. By employing suitable sequenced speckle patterns, we can achieve higher CNR and resolution while reducing computational resources compared to traditional random speckle patterns. The simulation results validated the experimental findings regarding CNR and resolution improvements. The DMD device proves to be highly effective in projecting sequenced random speckle patterns, allowing easy control over the speckle size for speckle projection. This feature makes it well-suited to investigating the influence of sequenced random speckle patterns on GI quality. Moreover, the sequenced random speckle pattern exhibits potential in imaging objects with unknown or complex shapes, enabling effective characterization of image contours. It is important to note, however, that while the sequential speckle method may not provide a comprehensive solution for achieving high-quality imaging of arbitrary targets, it demonstrated enhanced robustness across a wide range of cases. Furthermore, this approach can be easily extended to PGI using a rotating ground glass.  
We anticipate that these improvements will prove valuable in practical applications of both CGI and PGI, offering enhanced imaging capabilities and broadening the scope of potential applications.  
Figure 10: Evolution of the retrieved CNR with iteration for the SGI and TGI with similar resolutions in the experiment. The dotted line represents the CNR of 1.8873 for the TGI after 9000 iterations, while DG-6-3 and DG-2-5 achieve comparable CNR values with only 705 and 813 iterations, respectively. The required number of iterations is reduced significantly. To provide a clearer representation of the CNRs for different groups, the data between 1.50 and 2.50 are shown.  
**Author Contributions:** [PERSON] conducted the experiments and performed the simulations. [PERSON] conceived the idea, analyzed the results, and wrote the manuscript. [PERSON] participated in discussion and provided theoretical validation. [PERSON] reviewed the manuscript and supervised the project. [PERSON] and [PERSON] have contributed equally. All authors have read and agreed to the published version of the manuscript.  
**Funding:** Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany's Excellence Strategy--EXC 2051 (Project-ID 390713860), \"Balance of the Microverse\"; The Free State of Thuringia within the project \"Quantum Hub Thuringen\" (Funding ID 2021 FGI 0044); DAAD (Deutscher Akademischer Austauschdienst) German Academic Exchange Service, Funding programme/-ID: (57552340) Research Grants--Doctoral Programmes in Germany, 2021/22; The Fundamental Research Funds for the Central Universities (D5000220481).  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** Data available on request due to restriction of privacy. The data presented in this study are available on request from the corresponding author. The data are not publicly available due to related experiments are still in progress and involve unpublished papers.  
**Acknowledgments:** The author would like to thank [PERSON] for English checking.  
**Conflicts of Interest:** The authors declare no conflict of interest.