# Electro-Optical Imaging Technology Based on Microlens Array and Fiber Interferometer
## 4 Numerical Simulation of the Imaging System  
According to the point-source imaging simulation, as compared with the target source (Figure 3a), the reconstructed image (Figure 3c) is obviously poor. Therefore, we perform further simulations by changing the system parameters in order to evaluate the imaging resolution and quality. First, we only change \(\mathrm{N_{ob}}\), to simulate a resolution panel. With the same sampling interval, \(\mathrm{N_{ob}}\) determines the maximum interference baseline length (\(\mathrm{B_{max}}\)). According to imaging Equations (1) and (2), the larger the interference baseline length, the richer the high-frequency information contained, and the higher the imaging resolution. The imaging achieved by the system when the maximum \begin{table}
\begin{tabular}{c c c c} \hline \hline  & **Parameters** & **Symbol** & **Value** \\ \hline \multirow{2}{*}{Object plane} & Scene side length & D & 30 m \\ \cline{2-4}  & Number of samples & \(\mathrm{N_{ob}}\) & 200 \(\times\) 200 \\ \hline \multirow{4}{*}{Aperture plane} & Sampling interval & \(\Delta\mathrm{u}\Delta\mathrm{v}\) & 0.33 m\({}^{-1}\) \\ \cline{2-4}  & Number of microlenses & \(\mathrm{N_{ap}}\) & 200 \(\times\) 200 \\ \cline{2-4}  & Diameter of microlens & r & 1 mm \\ \hline Image plane & Number of samples & \(\mathrm{N_{im}}\) & 1200 \(\times\) 1200 \\ \hline \multirow{2}{*}{System} & Wavelength & \(\lambda\) & 600 nm \\ \cline{2-4}  & Object distance & z & 10\({}^{5}\) m \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Simulation parameters of the imaging system. Figure 3: (a) Light intensity distribution of target source; (b) detected spatial frequency distribution; (c) image obtained by inverse Fourier transform. baseline (B\({}_{\text{max}}\)) is 1.5, 1.7, and 1.9 is shown in Figure 4a-c. It is obvious that the image resolution was up to the length of the maximum baseline. This result also provides a basis for improving the resolution of the imaging system. The Nyquist sampling density affects the detected spatial frequency distribution. An extremely small sampling density can result in the loss of target information. In contrast, a high sampling density leads to information redundancy. However, the minimum sampling interval is limited to the sub-aperture size (r). Therefore, we have performed several repeated digital simulation experiments on the relationship between sampling density and imaging quality. In this regard, we introduce a sharpness evaluation function to evaluate the image quality. The commonly used spatial domain functions for sharpness evaluation are listed in the literature, among which the spatial domain functions represented by the variance function and the entropy function perform better [19]. We use two imaging quality evaluation methods based on gray variance and entropy function. We use the resolution board as the source target and change the sampling interval. The relationship between the value of the gray-scale variance and entropy and the sampling interval is shown in Figure 5. We see that the imaging quality can be improved by increasing the sampling density, although these two evaluation functions are not sensitive to small local changes. In addition, the imaging system has no oversampling when the minimum sampling density is equal to the sub-aperture size (\(\triangle\)u = 0.33). Thereafter, we used a photograph of an airplane (Figure 6) as the original target to perform the same simulation. Based on the results (Figure 7), we draw the same conclusion, although we compare the image quality visually in this case. Figure 4: (**a**) Image obtained when B\({}_{\text{max}}\) = 1.5 m; (**b**) Image obtained when B\({}_{\text{max}}\) = 1.7 m; (**c**) Image obtained when B\({}_{\text{max}}\) = 1.9 m.  
It is well known that different sources have different frequency information. For some sources, the frequency information was concentrated in the low-frequency part; therefore, the sampling density was increased to obtain a high-quality image. This resulted in a corresponding increase in system frequency.