Split Lohmann computer holography: fast generation of 3D hologram in single-step diffraction calculation

Holographic display stands as a prominent approach for achieving lifelike three-dimensional(3D)reproductions with continuous depth sensation.However,the generation of a computer-generated hologram(CGH)always relies on the repetitive computation of diffraction propagation from point-cloud or multiple depthsliced planar images,which inevitably leads to an increase in computational complexity,making real-time CGH generation impractical.Here,we report a new CGH generation algorithm capable of rapidly synthesizing a 3D hologram in only one-step backward propagation calculation in a novel split Lohmann lens-based diffraction model.By introducing an extra predesigned virtual digital phase modulation of multifocal split Lohmann lens in such a diffraction model,the generated CGH appears to reconstruct 3D scenes with accurate accommodation abilities across the display contents.Compared with the conventional layer-based method,the computation speed of the proposed method is independent of the quantized layer numbers,and therefore can achieve real-time computation speed with a very dense of depth sampling.Both simulation and experimental results validate the proposed method.

High efficiency generation of tunable ellipse perfect vector beams

We present a highly efficient method of generating and shaping ellipse perfect vector beams (EPVBs) with a prescribed ellipse intensity profile and continuously variant linear polarization state. The scheme is based on the coaxial superposition of two orthogonally polarized ellipse laser beams of controllable phase vortex serving as the base vector components. The phase-only computer-generated hologram is specifically designed by means of a modified iteration algorithm involving a complex amplitude constraint, which is able to generate an EPVB with high diffraction efficiency in the vector optical field generator. We experimentally demonstrate that the efficiency of generating the EPVB has a notable improvement from 1.83% in the conventional complex amplitude modulation based technique to 11.1% in our method. We also discuss and demonstrate the simultaneous shaping of multiple EPVBs with independent tunable ellipticity and polarization vortex in both transversal (2D) and axial (3D) focusing structures, proving potentials in a variety of polarization-mediated applications such as trapping and transportation of particles in more complex geometric circumstances.

Learning-based phase imaging using a low-bit-depth pattern

Phase imaging always deals with the problem of phase invisibility when capturing objects with existing light sensors.However,there is a demand for multiplane full intensity measurements and iterative propagation process or reliance on reference in most conventional approaches.In this paper,we present an end-to-end compressible phase imaging method based on deep neural networks,which can implement phase estimation using only binary measurements.A thin diffuser as a preprocessor is placed in front of the image sensor to implicitly encode the incoming wavefront information into the distortion and local variation of the generated speckles.Through the trained network,the phase profile of the object can be extracted from the discrete grains distributed in the low-bit-depth pattern.Our experiments demonstrate the faithful reconstruction with reasonable quality utilizing a single binary pattern and verify the high redundancy of the information in the intensity mcasurement for phase recovery.In addition to the advantages of efficiency and simplicity compared to now available imaging methods,our model provides significant compressibility for imaging data and can therefore facilitate the low-cost detection and efficient data transmission.

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.

Curvilinear Poincaré vector beams

We develop a method for completely shaping optical vector beams with controllable amplitude, phase, and polarization gradients along three-dimensional freestyle trajectories. We design theoretically and demonstrate experimentally curvilinear Poincaré vector beams that exhibit high intensity gradients and accurate state of polarization prescribed along the beam trajectory.