Effective method for further magnifying the image in holographic projection under divergent light illumination

Divergent light illumination can effectively increase the diffraction angle of holographic projection. However, the achieved maximum image size is limited to the geometric enlargement of the hologram size with the existing double-sampling Fresnel diffraction algorithm. In this paper, an effective method for further magnifying the image is proposed. The theoretical maximum size under divergent illumination is first analyzed. On this basis, a virtual intermediate plane is introduced between the source plane and the image plane. Then three-step diffraction calculation is performed to evaluate the Fresnel diffraction between the hologram plane and the image plane so that the sampling interval on the image plane is related to the position of the virtual plane and can be flexibly tuned. Consequently, the achieved image size can be further enlarged. The feasibility of the proposed method is demonstrated by simulations and experiments.