Research On Key Technologies Of High Density Small Pitch LED-based Integral Imaging Display System

Ture 3D video generation and large screen display have become the ultimate goal of future stereoscopic video development.Integral imaging technology has become a hot spot research because it can reproduce stereoscopic scenes with continuous parallax,bright colors and real stereoscopic scene.The key to the development of integral imaging is how to generate elemental image array,realize high-definition large screen display and effectively evaluate system performance.In this work we focus on the key technologies of high-density small-pitch LED-based integral imaging display system and the main innovative points of this work are as follows:1.Efficient content generation algorithm based on integral imaging.For the elemental image with high resolution,the computation cost is large and the rendering time is long.To solve this problem we propose a method which can generate the elemental image array quickly by using window interception.The acquisition model of optical information is established according to the structure of the lenslet array and the optical parameters of display platform.The projection of the object on the acquisition plane,that is,the view point images which corresponds to each virtual lens are calculated by parallel ray tracing rendering.And the calculated view point images are intercepted and stitched according to the shape of the lens by using a window function to generate the elemental image array.This method can improve the rendering efficiency with high fidelity.The elemental image array with any aperture and any arranging structure can be generated by changing the window function.The recording direction of the elemental image array is opposite to the watching direction when display,which cause the depth information of the 3D image is reverse to the real object.Therefore,we propose a method based on reference plane to generate the elemental image array without pseudoscopic viewing.By analyzing the correspondence between the observing plane and the reference plane,an optical mapping and pixel matching model is built and the elemental image array without pseudoscopic viewing is calculated using back projection.Various display modes such as real,virtual,and both of them can be realized by changing the position of the reference plane and the 3D effect can be enhanced.The mixture of virtual and reality elemental image array generation method is proposed since the computer is incapable of acquiring the elemental image of real scene.The 3D model of the real object is built and merged with the virtual one,and the ray tracing rendering is used to generate the mixture of virtual and reality elemental image array.Consequently,the scene content is enriched and the problems such as small viewing angel in lenslet array directly pickup or big interval and discontinuous parallax in camera array collection can be avoided.2.Construction of integral imaging display system and optical parameter matching and optimization of lenslet array.We propose the overall construction scheme of integral imaging display system and optical parameter optimization method.The key to achieve large-screen display of integral imaging is the large size high resolution display device and its optically matched lenslet array.The emergence of high-precision flip chip Mini LED has decreased the pixel pitch and the technical bottleneck of LED display applied to integral imaging display system has been broken.At the same time the color gamut,brightness,viewing angle,refreshment frequency and the use range of LED display are better than LCD and projector.In this work we construct the high density small pitch LED-based integral imaging display system by optimal matching the LED display module with pixel pitch of 1.25 mm and the lenslet unit as an integral imaging display unit.Large screen display can be implemented by seamless stitching the high density small pitch LED display module and the optimized optical parameter matching of the lenslet unit solves the problem of difficulty in manufacturing large size lenslet arrays.According to the display space,a certain number of integral imaging display unit can be combined to realize a variety of large screen stereoscopic display such as plane and arc.In order to explore an effective way to improve the performance of integral imaging display system under limited information bandwidth,the circular,square and hexagonal lenslet arrays with different inscribed circle diameter are designed.Experimental results show that the proposed integral imaging display system based on different aperture and high density small pitch LED can reconstruct the 3D image with approximately continuous horizontal and vertical parallax,bright color and realistic effects.Compared with the imaging effects of different lenslet arrays,it can be seen that the 3D image reconstructed by the hexagonal lenslet array with higher filling rate and sampling rate is clearer.3.Evaluation model of integral imaging display system.Generally,the function used to evaluate the performance of an integral imaging display system is proposed under the condition that the horizontal and vertical resolution of 3D image are same.Consequently,it is only applicable to square lenslet arrays.A performance evaluation model for integral imaging system using different lenslet arrays is proposed,which analyzed the relationship between the 3D image point and the shape,size,arrangement structure of the lenslet and the filling factor,sampling rate and diffraction of the lenslet array.We quantitatively analyze the impact of different lenslet arrays on system performance.In order to verify the performance metric results,an objective evaluation method is proposed using quality fluctuation of the 3D image reconstructed at different depth planes.Experiments compare the imaging effects of the designed three different lenslet arrays and the results show that the hexagonal lenslet array has the best display effect which is consistent with the subjective perception.