# Parallel Ghost Imaging with Extra Large Field of View and High Pixel Resolution
## 2 Experimental Methods and Results
For parallel ghost imaging with true magnification, which is prone to larger experimental errors, global ghost imaging improves reconstruction quality compared to other methods. However, due to the need to load all subsystems into memory for simultaneous computation, it places a considerable strain on computational resources.To address reconstruction efficiency, we perform the global ghost imaging reconstruction in blocks of 100 \(\times\) 100 pixels as a global domain and then stitch together the final result. Computational limitations currently restrict the use of global ghost imaging for extra-large field-of-view ghost imaging. This necessitates further modifications to the global imaging approach, which we aim to explore in future work. Figure 1: **(a)** Schematic diagram of the object arm in the parallel ghost imaging experiment. (**b**) The signal coupling between the object and speckle collected from (**a**). (**c**) Schematic diagram of the reference arm in high-resolution parallel ghost imaging experiment. (**d**) The high-resolution speckle patterns collected from (**b**). (**e**) Schematic diagram of the reference arm in extra-large FOV and high-resolution parallel ghost imaging experiment. (**f**) The extra-large field and high-resolution speckle patterns collected from (**e**). In fact, the potential of parallel ghost imaging has yet to be fully realized. The high-resolution speckle patterns collected by the reference arm detector (Figure 1d) actually only cover a small portion of the object arm detector's field of view (Figure 1b), as indicated by the red box. This suggests that we can further exploit the non-local nature of ghost imaging. When pre-recording the reference arm, instead of only capturing the set of speckle patterns with the magnification lens switched (while keeping the detector fixed), we can record the entire large, high-resolution speckle space corresponding to the object arm's field of view. This can be achieved by moving the detector in a grouped manner, recording each set of speckle patterns, and then stitching them together. This approach means that we will capture a total of \(7\times 5\) groups of speckle patterns, which takes about 5 h, as shown in Figure 1f. The experimental diagram for the reference arm, which enables both extra-large field-of-view and high-pixel resolution in parallel ghost imaging, is shown in Figure 1e. Finally, after completing the pre-recording of the reference arm, we successfully achieved parallel ghost imaging with an experimental efficiency of 6 min per sample. The resulting images had a size of 14,000 \(\times\) 10,000 pixels, a pixel resolution of 0.325 um, and good image quality. A total of 400 measurements were made, with a sampling rate of 400%, and the reconstruction results are shown in Figure 3.  
It is important to note that the substantial expansion of the field of view is an enhancement with no negative side effects. Due to the non-local nature of ghost imaging, the ionizing radiation dose absorbed by the sample in the object arm has not increased at all. Figures 2 and 3, which use the same set of speckle patterns from the object arm, provide strong evidence for this assertion. Furthermore, from an optical perspective, temporal coherence can also give rise to certain issues. The coherence of X-rays emitted by the synchrotron radiation source deteriorates over time, which leads to slight differences in the collected speckle patterns. This, in turn, results in the inability to eliminate background interference fringes in the reconstructed results. As the time interval increases, the interference fringes become increasingly prominent, which can be observed from the gradual enhancement of background fringes in the reconstructed results from the upper left to the lower right. Parallel ghost imaging shows great potential for achieving extra-large field-of-view and super-resolution imaging at a low cost. In fact, it can significantly reduce the X-ray dose, and we will continue to explore this in future work.