Fig. 1. U-Net network structure

Fig. 2. Five intensity distributions and holograms generated for training

Fig. 3. The on-axis holograms in training set and the reconstructed results

Fig. 4. The SSIM between U-Net results and the intensity distributions of the objects

Fig. 5. The on-axis holograms of phase objects and the corresponding phase distributions

Fig. 6. The test holograms and the results reconstructed by U-Net

Fig. 7. The difference between real phase distributions and the phase distributions reconstructed by Fig. 6（a）

Fig. 8. The on-axis digital holograms generated by the letter data set and the corresponding reconstruction results

Fig. 9. The reconstruction results of on-axis hologram of letter “F” under different noise levers