Methods For Enhancing Depth Of Field Of The Naked-eye Three-dimensional Light Field Display

Light field display technology can reproduce all the information of the scene in line with the perception habits of the human eyes,including color information,light intensity,direction information and depth information,so it is a three-dimensional(3D)displaytechnology based on light field reconstruction.Compared with traditional 2D display technology,3D light field display can provide depth information for reproducing the scene,and the amount of information is more substantial.Therefore,light field display technology can better help people understand the shape of the objective scene and improve work efficiency.However,there are still many problems to be solved at this stage,especially the limited depth of field,which restrict the development and application of light field display in various fields.In the traditional light field display based on lens array,depth of field,viewing angle,and viewpoint resolution compromise each other.Depth of field is the imaging property of 3D display systems and generally correlates with the parameters of a lens,which in turn necessarily changes the display properties such as viewpoint resolution and viewing angle.For example,in a 3D display,the depth of field can be elevated by decreasing the lens aperture,but a small aperture lens decreases the viewing angle,and increases viewpoint resolution instead.Therefore,aiming at the trade-off issue of limited depth of field,the key technologies for improving the depth of field of light field display while ensuring high resolution and large viewing angle are proposed in this dissertation.The main research contents and innovations of this dissertation are as follows:(1)Depth of field analysis of 3D light field display based on holographic function screenAiming at the unknown reason of limited depth of field based on holographic function screen light field display,a depth of field analysis method based on pixel deviation effect is proposed.By analyzing the imaging characteristics of the integrated imaging display system after introducing the holographic function screen,the direct reason affecting the reproduction depth of field,the pixel deviation effect,is explained.Then,the mathematical relationship between the degree of pixel deviation and the parameters of the display system is deduced,and the depth of field model based on holographic function screen light field display is established.The simulation results show the accuracy of calculating the depth of field with the proportion of pixel deviation.Finally,the effectiveness of the simulation results is verified by the optical reproduction experiment.As an important reference formula,the proposed depth of field model can reproduce the clear depth of field range to the greatest extent,which has guiding significance for the lens parameter design of optical system.(2)Depth of field enhancement method of 3D light field displayAiming at the difficulty of improving the depth of field in light field display,a light field display method based on depth-layered multi-view fitting coding algorithm is proposed on the basis of reproducing the depth-of-field model.The method is implemented by a light field display system composed of a holographic function screen and a lens array,and mainly performs weight calculation processing for different depth layers of a 3D image.is related to the degree of pixel deviation.By constructing a light field display model,the principle of multi-view fitting with fusion characteristics is analyzed,and the solution of the weight matrix and the initial coded image are determined by least squares fitting.The results of simulation experiments and optical experiments show that the proposed fitting algorithm can minimize the influence of pixel deviation on the depth of field of the display system,and the maximum clear depth of field reproduced by the light field display system is increased from 125 mm to 140 mm,which enhances the light field.Field display system visualization.(3)Large viewing angle and enhanced depth of field light field display based on optimized viewpoint distributionIn order to improve the depth range and viewing angle at the same time,a new light field display system based on the optimal distribution of non-uniform viewpoints is presented.In order to improve the viewing angle,the lens array is composed of a composite light control structure with a wide pitch.Because the opaque mask used by the composite structure reduces the light intensity,the display system uses 54-inch LED as the display source to increase the display brightness.The cylindrical lenses in this composite lens array are stepped arranged.Under the combined modulation by the holographic function screen,vertical pixels are used to construct horizontal viewpoints,which ultimately result in a sparse arrangement of viewpoints on both dense sides in the middle.This non-uniform viewpoint arrangement improves the depth range of the intermediate viewport,and effectively balances the internal relationships among the number of viewpoints,viewing angle and depth of field.Experiments show that the display system can reconstruct 160 viewpoints with a 65° viewing angle,the depth of field in the center of the viewing area is increased to 300 mm,which meets the expectation of reproducing a 3D scene with a clear and wide field depth range.