Investigation On Light Field Holography Algorithm Based On Complex Modulation

The holographic display can reconstruct the complete light field of any three-dimensional scene,and can provide all the depth clues needed by the human eye to perceive the world,thus becoming the most attractive display technology in the future three-dimensional display field.With the rapid development of computer technology and silicon-based liquid crystal technology,computer holograms becomes more and more popular due to their unique features such as simple production,easy storage,and wide range of uses,which have freed us from complex interference systems and high precision operation requirements.However,when using computer holograms for three-dimensional reconstruction,there are still some problems,such as speckle noise,field angle,and depth of field,which restrict the development and progress of holographic displays.This article focuses on the depth of field in holographic display.By combining the idea of light field control based on the complex amplitude modulation algorithm,more and more accurate depth clues can be obtained without affecting the reconstruction quality,making the depth of field effect more natural,which can expand the application scenarios of holographic display in the future.This article first briefly describes the development process of holography and computational holography,and introduces the current status and problems of computational holography research at home and abroad.Then from the theoretical aspect,the scalar diffraction theory in Fourier optics and the numerical calculation method of hologram are introduced,and the algorithm and advantages of phase hologram are discussed.On this basis,the method of complex amplitude modulation is mainly discussed,and the depth of field of the image in holographic reproduction is considered.The main innovations of the article are as follows:1?The complex amplitude modulation with double-phase encoding algorithm is studied,and the reason why the depth of field range of the holographic display image is large is that the uniform phase of the algorithm results,that is,the uniform phase causes the spectrum range of the hologram to be narrow.Therefore,this paper uses the G-S(Gerchberg-Saxton)iterative method to expand the spectrum range of complex amplitude.The algorithm idea is as follows:First,the original image is filtered to obtain the amplitude map of the depth of field change,and then the G-S loop iteration is used to gradually approximate the depth of field of the reconstructed image and the natural scene.Through simulation and optical experiments,it is found that compared with the original two-phase coding algorithm,the reconstructed image in this method expands the spectrum range,and the image is naturally blurred outside the reconstruction plane.2?The holographic display method based on light field is studied,from the aspects of light field display technology and acquisition method of natural light field.It includes three light field display technologies: light field-based holography based on light,light field-based holography based on wavefront,and mixed light field holography based on light and wavefront.And two methods of obtaining natural light field: perspective projection geometry and orthogonal projection geometry.Finally,it is analyzed that the holographic display method based on the light field can contain more and more accurate depth clues required by human eye perception,and then reconstruct the effect closer to the natural scene.3?Based on the research of complex amplitude modulation and light field holography,it is proposed to introduce light field information into the hologram calculation model on the basis of complex amplitude modulation,so as to obtain more accurate depth clues.The algorithm idea is as follows: First,the ray sampling(RS)plane is used to capture the perspective projection sub-image of the three-dimensional scene.Secondly,the tilt plane phase factor corresponding to each viewpoint is calculated according to the spatial coordinate position of each viewpoint,and each image is multiplied by the tilt plane phase factor corresponding to its angle information.Finally,each image is added directly in the spatial domain to obtain a complex amplitude hologram.Also through simulation and optical experiments,the depth of field effect of this method is verified,which shows that the simple accumulation of light field information can improve the spatial bandwidth product of holographic imaging and improve the quality of the displayed image.