Image magnified lensless holographic projection by convergent spherical beam illumination

In liquid crystal spatial light modulator (SLM)-based holographic projection, the image is usually displayed at a distant projection screen through free space diffraction from a computer-generated hologram (CGH). Therefore, it allows for removing of the projection lens for the sake of system simplification and being aberration free, known as the "lensless holographic projection". However, the maximum size of the optical projected image is limited by the diffraction angle of the SLM. In this Letter, we present a method for the implementation of image magnification in a lensless holographic projection system by using convergent spherical wave illumination to the SLM. The complete complex amplitude of the image wavefront is reconstructed in a lensless optical filtering system from a phase-only CGH that is encoded by the off-axis double-phase method. The dimensions of the magnified image can break the limitation by the maximum diffraction angle of the SLM at a given projection distance. Optical experiment results with successful image magnification in the lensless holographic projection system are presented.