Research On Correction Method Of Uneven Distribution Of Viewpoints In Three-Dimensional Light Field Display

Three-dimensional display technology can display objects with complete spatial information including depth,which has a strong application demand in many fields including medical,military and education.Among numerous three-dimensional display technologies,light field display has attracted much attention because of its ability to provide large scale and high quality dynamic three-dimensional experience.Light field display constructs voxels in space to represent luminous points on real objects.Light beams emitted from voxels in different directions carry different spatial information.Natural three-dimensional display can be achieved after encoding the beams to reconstruct original light field of objects.Various methods to realize light filed display have been proposed by scholars at home and abroad.Extensive researches on viewing angle,spatial resolution and number of viewpoints have been conducted to improve performance.However,the analysis of the uniformity of viewpoint distribution has often been ignored.It is found that the problem of uneven distribution of viewpoints is common in most light field display systems,which will lead to perspective relation errors and other problems in displayed images and affect the accuracy and effectiveness of the reconstructed spatial information.The correction method of uneven distribution of viewpoints is studied in this thesis.The main innovation points and research content of this dissertation are as follows:(1)A correction method of uneven distribution of viewpoints based on viewpoint-matching pixel encoding is proposed.In light filed display systems based on cylindrical lens arrays,the distribution of viewpoints is uneven due to lens distortion.Distortion becomes severer with the increase of viewing angle.It is found that the uneven distribution of viewpoints will lead to mismatch between the reconstructed images and the viewpoint positions,resulting in the wrong perspective relation of the displayed image and affecting the viewers’perception on spatial depth.A real-time rendering method of synthetic image based on viewpoint-matching pixel encoding is proposed.The method makes the reconstructed image match the non-uniform viewpoints without modifying the system hardware.The experiments show that this method increases the average SSIM value between the displayed image and the original image from 0.7693 to 0.8135,effectively solving the problem of incorrect perspective relation of displayed images and improving the display quality.(2)A correction method of uneven distribution of viewpoints based on optimization of lenticular aberration is proposed.In tabletop light filed system based on directional backlight,the distribution of viewpoint is nonuniform due to the lenticular aberration,especially spherical aberration.The light beams emitted from the backlight source cannot converge to an ideal point but create a shape of dispersion spot on the focal plane after passing through the lens,which leads to uneven distribution of viewpoints,with dense distribution in the middle of the viewing area and sparse distribution at the edge.Analysis shows that the uneven distribution of viewpoints not only causes the incorrect perspective relation in the displayed image,but also causes the crosstalk between the adjacent viewpoints and reduces the display clarity.A method of optical optimization of lenticular lens array by introducing a aspheric surface is proposed to reduce aberration,which essentially improving the uniformity of viewpoint distribution from 39.32%to 98.39%,and effectively solving the problem of perspective relation error and crosstalk between adjacent viewpoints.