| We are living in a three-dimensional world.When we observe the surrounding scenery through our eyes,we will not only receive the color and light intensity information from the surface of the object,but also obtain the spatial depth information,which helps us to judge the size,distance and position of the object.However,the traditional flat display device can only display the two-dimensional(2D)projection image of one side of the three-dimensional scene,which loses the depth information,and seriously affects people's three-dimensional spatial information acquisition,processing and expression.Naked eye three-dimensional(3D)display technology can reproduce stereo images with spatial depth information for viewers without wearing any visual aids.Therefore,it is considered to be the main development direction in the next generation of display technology,and has been widely concerned by researchers and enterprises in various countries.Among many naked eye 3D display technologies,light-field display technology can truly restore the light field distribution of objects and achieve realistic and natural 3D display effect.It is recognized as one of the most promising 3D display technologies.However,there are still some problems in the light-field display technology,such as limited viewing angle,high crosstalk,low image resolution and so on,which restrict its development and application.In order to achieve high-quality 3D light-field display effect,this paper studies the key technologies to improve the performance of 3D light-field display.The main research content and innovation points of this dissertation are as follows:(1)Wide-viewing-angle light-field display technology based on viewing-zone-stitching of voxelsIn order to solve the problem of the limited viewing angle in the light-field display technology,a wide-viewing-angle light-field display method based on viewing-zone-stitching of voxels is preposed.In this method,the multi-directional collimating light source is adopted to replace the scattering light source in the traditional light-field display systems.Combined with the lens array,it can realize the construction of dense voxels and the stitching of multiple viewing areas.As a result,the inherent contradiction between viewing angle and image resolution can be resolved,and the viewing angle of the light-field display can be significantly improved under the condition of ensuring the image resolution.Based on the proposed display method,a time-multiplexed light-field display system with large viewing angle is demonstrated.In the system,the LCD panel is adopted as the display source for the light-field display.With the alternate illumination of three groups directional backlights and the synchronous refreshing of coded images on LCD,the three constructed viewing areas can be spliced up in a time-multiplexed way.Finally,a clear 3D display effect with a large viewing angle of 120 degrees can be achieved.(2)Analysis and removal of crosstalk in a time-multiplexed light-field displayIn order to solve the crosstalk issues in the time-multiplexed light-field display system,this dissertation introduces and analyzes two different types of crosstalk in the system:structural crosstalk and optical crosstalk.For structural crosstalk,a crosstalk suppression method based on the ladder-type LCD sub-pixel arrangement is proposed,which reduces the average value of structural crosstalk from 20.3%to 0%.For optical crosstalk,a compound aspheric lens-array is proposed,which can achieve a uniform distribution of the emergent light,and the maximum optical crosstalk is reduced from 17.3%to 0.26%.Simulation and experimental results indicate that the depth range of clear 3D image is significantly improved based on the two crosstalk suppression methods proposed in this paper.(3)Resolution enhancement technology of integral imaging light-field display systemIn the traditional integral imaging system,due to the existence of lens aberration,the human eye can only see one pixel in the element image through each lens,which leads to the insufficient resolution of 3D image reproduction.To solve this problem,an integral imaging display method based on holographic function screen is proposed in this dissertation.This method can effectively suppress the aberrations of the lens,so that the human eye can observe multiple pixels in the element image through each lens,and significantly improve the 3D image resolution.In addition,by setting the diffusion angle of the holographic function screen,the lens gap can be eliminated visually,which can improve the uniformity and the smoothness of the 3D image.Based on the improved integral imaging system,a coding method of the element image based on multi-ray fitting algorithm is proposed,which can achieve high-precision light-field reconstruction.Simulation and experimental results show that the proposed method can produce a clear and uniform 3D image with full-parallax in a 400 viewing angle. |
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