三步无混叠采样菲涅耳衍射实现大视场全息显示

Large Field-of-View Holographic Display Realized by Three-Step Non-Aliasing Sampling Fresnel Diffraction

提出一种大视场全息显示方法,在空间光调制器前方引入一个短焦凸透镜,并根据光经过凸透镜时先聚焦再发散的性质执行三步菲涅耳衍射,通过调控凸透镜所在平面、凸透镜焦平面、观察平面3个平面的位置,扩大观察平面的显示范围。同时针对此结构,提出相匹配的三步无混叠采样菲涅耳衍射算法,避免了传统菲涅耳衍射算法中由欠采样造成的混叠误差,最终实现高质量的大视场全息显示。通过仿真和光学实验验证了所提方法的可行性和有效性,其可用于大视场全息投影、大衍射图案的光束整形等领域。

Objective Holographic display technology can fully capture and reproduce the wavefront information of 3D light fields,making it the most promising 3D display technology.With the advancement of spatial light modulators(SLMs),they have become integral to holographic display systems,typically used to load phase-only holograms for modulating incident light.Holographic display technology based on SLMs digitizes recorded objects to generate holograms,simulating the propagation of object light.This allows reproduction not only of real objects but also virtual ones,unconstrained by the physical form of the object.However,current SLM structures limit the size of holographic reconstruction images,often failing to meet the demands of large field-of-view holographic displays.This paper proposes a method for achieving large field-of-view holographic displays.It involves placing a short focal length convex lens in front of the SLM.By utilizing the lens’s property of focusing and then diverging light,a three-step Fresnel diffraction process is implemented.Adjusting the position of the convex lens plane,its focal plane,and the observation plane expands the display range of the observation plane.Furthermore,to mitigate aliasing errors caused by undersampling in traditional Fresnel diffraction algorithms,a novel three-step non-aliasing sampling Fresnel diffraction algorithm is introduced.This approach ultimately enables large field-of-view holographic displays with high quality.Methods The holographic display system comprises an SLM and a short focal length convex lens.Leveraging the convex lens’s property of focusing light before diffusing it,and considering the size relationship between objects and images in the Fresnel diffraction algorithm based on a single fast Fourier transform(FFT),we adjust the positions of the convex lens plane,its focal plane,and the observation plane to enlarge the reconstructed image.Next,we propose a three-step non-aliasing sampling Fresnel diffraction algorithm tailored to this setup.Different optimizations are applied to each diffraction calculation step to mitigate sampling errors inherent in traditional Fresnel diffraction methods.Finally,we employ the Gerchberg‒Saxton(GS)algorithm for iterative optimization to generate accurate phase-only holograms.Results and Discussions The generated hologram is utilized for simulation and optical experiments,comparing it with traditional methods.Simulation results demonstrate that the proposed approach significantly enlarges the field-of-view of the reconstructed holographic image and eliminates aliasing interference,thereby improving the reconstruction quality(Fig.5).Experimental results corroborate the simulation findings(Fig.7).The proposed method effectively mitigates the zero-order background noise originating from the SLM,which is focused at the focal plane of the convex lens and subsequently diffused over increased diffraction distances.However,the periodic pixel structure of the SLM still induces higher-order diffraction images on the observation plane.Additionally,pixel interactions on the SLM induce fringe field effects,causing unintended phase variations among neighboring pixels.This can result in image artifacts,reduced modulation fidelity,and inaccurate wavefront manipulation.Conclusions In this paper,we propose a method for large field-of-view holographic display.The holographic display system consists of an SLM and a short focal length convex lens.It utilizes a three-step Fresnel diffraction process,leveraging the optical properties where light passes through the convex lens to focus and then disperse.By modulating the positions of the convex lens plane,focal plane,and observation plane,the field-of-view at the observation plane is effectively enlarged.Building upon this framework,we introduce a three-step non-aliasing sampling Fresnel diffraction algorithm to mitigate aliasing issues inherent in traditional methods,thereby enhancing calculation accuracy.Finally,a phase-only hologram is generated using the GS algorithm.Experimental results in optics align closely with numerical simulations.Compared to alternative methods,this approach is characterized by simplicity and efficiency,requiring minimal additional optical components.It holds promise for applications such as large field-of-view holographic projection,beam shaping for expansive patterns,and other related fields.