# Computer-Generated Hologram Based on Reference Light Multiplexing for Holographic Display
## 4 Optical Experiments  
In order to verify the viability of the proposed method, we executed optical experiments. The resolution of the CGH was 1080 \(\times\) 1920 and the pixel size was 8 \(\upmu\)m \(\times\) 8 \(\upmu\)m. The schematic of the experimental setup for reconstruction is shown in Figure 6. The zero order beam introduced by a SLM on the reconstructed images was eliminated by the 4f system, which consists of two lens and a filter [44]. In the optical experiments, a flat reflection-type SLM and plane reference wave with a wavelength of 532 nm was used. The reconstructed images were captured by a CCD.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Image** & **RMSE** & **SC** \\ \hline pepper & 0.232 & 0.367 \\ cameraman & 0.244 & 0.292 \\ baboon & 0.254 & 0.369 \\ woman & 0.221 & 0.345 \\ man & 0.234 & 0.353 \\ girl & 0.238 & 0.300 \\ sailboat & 0.248 & 0.351 \\ bridge & 0.236 & 0.322 \\ \hline \hline \end{tabular}
\end{table}
Table 2: RMSE and SC of numerical results.  
Figure 5: Numerical reconstructions; (**a**) ‘pepper’, (**b**) ‘cameraman’, (**c**) ‘baboon’, (**d**) ‘woman’, (**e**) ‘man’, (**f**) ‘girl’, (**g**) ‘sailboat’, (**h**) ‘bridge’ are target images, and (**i**–**p**) are corresponding reconstructed images with 20 iterations.  
In order to reconstruct different images, the phase distribution \(\Phi_{\text{MCGH}}\) of the MCGH must be precompensated before loading on the SLM. The phase distribution \(\Phi_{\text{R}}\) of reference light wave is added to the MCGH, which is the equivalent of changing the plane reference wave to a cylindrical or spherical reference light wave. After compensation, the phase distribution \(\Phi_{\text{SLM}}\) can be written as:  
\[\Phi_{\text{SLM}}=\Phi_{\text{MCGH}}+\Phi_{\text{R}} \tag{13}\]  
In optical experiments, we first reconstructed four independent images at the same position. Different cylindrical precompensated phases were added to the MCGH before loading on the SLM. In this way, different images, including 'pepper', 'cameraman', 'baboon', and 'woman', were all reconstructed successfully, as shown in Figure 7; the corresponding evaluation parameters are shown in Table 3. It can be observed that the optical reconstructions were in good agreement with the numerical reconstructions and there is little crosstalk in the reconstructed images.  
We also reconstructed eight independent images at different positions. Different spherical precompensated phases were added to MCGH. The reconstructed images are presented in Figure 8, where Figure 8a-d are located at 200 mm and Figure 8e-h are located at 210 mm. The corresponding evaluation parameters of the reconstructed images are shown in Table 4. It can be remarked that the proposed method achieves high reconstruction quality and the optical reconstructions agree with the numerical reconstructions perfectly. With the knowledge gained from these results, the proposed method can further realize  
Figure 6: Schematic of a holographic display system. SLM is the spatial light modulator, PC is the personal computer, L1 and L2 are the Fourier transform lens.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Image** & **RMSE** & **SC** \\ \hline pepper & 0.293 & 0.258 \\ cameraman & 0.322 & 0.296 \\ baboon & 0.294 & 0.244 \\ woman & 0.257 & 0.278 \\ \hline \hline \end{tabular}
\end{table}
Table 3: RMSE and SC of optical reconstructions.  
Figure 7: Optical reconstructions from (**a**) ’pepper’, (**b**) ’cameraman’, (**c**) ’baboon’, (**d**) ’woman’.  
multiplexed information capacity with other multiplexing methods, indicating that the proposed method is flexible and has great potential for dynamic holographic display.