The Key Technology Research Of The 3d Light Field Display With Large Depth Range And Wide Viewing Angle

The three-dimensional information is crucial for us to fully understand and accurately judge things in living and working scene.However,the traditional plane display device can only show two-dimensional information to the viewers,which loses depth information and then cannot meet the requirements of various industries for the visualization of three-dimensional data and depth information.In recent years,3D display technology has drawn extensive attention of scholars at home and abroad,which can show depth information of the real scene to the audience.Autostereoscopic display technology includes multi-view 3D display and light field display,with which audience can perceive 3D images without any auxiliary glasses.Light field display is considered as the main development direction of the autostereoscopic display technology,which can simulate the light field information of the original 3D scene.However,there are some drawbacks of the light field display need to be solved,such as small depth of field and narrow viewing angle.Here,the key technology of the light field display with large depth of field and wide viewing angle is investigated and developed.The main research content and innovation points of this dissertation are as follows:(1)The analysis method and the improved method of the depth of field for the integral imaging light field displayKey point 1:The depth of field of integral imaging is influenced by the record process and display process.If camera shoots an object out of the focus plane,the captured image on the CCD is composed of speckles.Here,the depth range of the integral imaging in the pickup process is derived by analyzing the optical characteristics of the lens,the acceptable size of speckles and the correct perspective distance.Key point 2:The common methods to analyze the depth of field are based on wave optics.However,the lens aperture of integral imaging system is approximately 104 times of the wavelength of the visible light,thus the diffraction effect is negligible.Here,the phenomenon of facet braiding is analyzed,and then the model of depth of field in the display process is analyzed based on this phenomenon.After the light rays emitted from a sub-image pass through the corresponding lens,an image unit is formed in the image plane.The 3D image is integrated by these image units.The contradiction between the characteristic of lens imaging and the process of light rays intersect to form 3D image appears when the reconstructed plane is away from the image plane of lens,then these image units cannot be stitched as a complete 3D image.This contradiction affects the image quality and reduces the depth of field.Here,the depth range is derived by analyzing this contradiction.Key point 3:An integral imaging display method based on time multiplexing technology is proposed,which can eliminate the influence of facet braiding and improve the depth of field.The display method is realized by high-brightness backlight,pinhole array and liquid crystal.Compared with lens,the advantage of pinhole array is that it has no reference plane.After the light rays emitted from elemental image array pass through the pinhole array,the 3D image corresponding to the different depth scenes will be reconstructed at the original position of the object.Therefore,if the image arrays corresponding to different depth plane are refreshed rapidly on the LCD,audience can simultaneously view the images of multiple depth planes because of the visual staying phenomenon.Thus,the depth of field of the display system is improved.(2)The light field display based on integral imaging and holographic functional screenKey point 4:Here,a light field display system with wide viewing angle based on integral imaging and holographic functional screen is proposed,which is composed of LCD device,lens array and holographic functional screen.In the proposed system,a compound lens array with a large pitch is designed,which can effectively improve the viewing angle.The compound lens can suppress aberrations and improve the image quality.The proposed holographic screen can modulate the light rays emitted from the lens array and smooth the distribution of the light field.Key point 5:Here,a method for acquiring 3D data with off-axis cameras and generating elemental image array is proposed.The way of off-axis shooting is consistent with the way of human viewing real obj ects.The common shooting area of the cameras is large and no redundant information is recorded.The pixel mapping procedure in image encoding algorithm is a point-to-point process,thus the arrangement of viewpoint information is precise.(3)The large scale light field display based on aspheric lens array and holographic functional screenKey point 6:Here,a large-scale light field display system with wide viewing angle is introduced,which is composed of LED device,aspheric lens array and holographic functional screen.In order to improve the viewing angle,an aspheric lens array with a large pitch is designed.The aspheric lens is designed to suppress aberrations and improve the image quality.Compared with the spherical lens,the imaging performance of the designed aspheric lens is better.To improve the viewpoints along the horizontal direction and obtain a continuous and smooth 3D image,a lens structure with inclined arrangement is designed.With this structure,the pixels in the vertical direction is used to construct the viewpoints in the horizontal direction.Combined with the holographic function screen,a large-scale high quality light field display system is realized.