Study On Plenoptic Imaging Method Based On Object Space Depth Addressing

As a kind of three dimensional(3D)imaging mode based on microlens array with needed surface profile,many architectural approaches about the plenoptic imaging have been developed.The latest plenoptic cameras applied in industry are mainly composed of several microlens arrays with different fixed focal length.The microlenses with given focal length are used to clearly imaging objects positioned at different object space site so as to extend the depth of field(Do F)of the imaging system.But their 3D imaging ability is still limited and also not compatible with current mature planar imaging mode.The liquid crystal microlens arrays(LCMLAs),as a kind of control lightwave micro-nano-device with tunable focal length for replacing the common microlens arrays having fixed focal length,can be utilized to implement plenoptic imaging so as to demonstrate a larger Do F and an unique ability of addressably tomographic object space,and further being compatible with current planar imaging mode.In this dissertation,several problems such as improving plenoptic image efficiency and realizing highly efficient control lightwave through constructing the LC-based plenoptic camera,and further performing autofocusing to multi-object environment are deeply researched based on increasing beam utilization efficiency of the LCMLAs.The main work is as follows:Firstly,a LCMLA with dense arranging hexagons(Hexagonal-LCMLA)is proposed.Based on excellent electrophoto characteristics of nematic LC materials and the elastic continuum theory,the LC layer driven according to the patterned electrode is simulated by both the relaxation and the finite difference methods.The director of LC molecules and the lightwave phase retardation transmitting through the LC cavity with different LC layer thickness and the intensity of spatial electric field applied over the LC layer are analyzed.A type of LCMLA component with typical patterned aluminum electrode is fabricated by common photolithography and wet etching process.The design parameters of a plenoptic camera based on the LCMLA formed by densely arranging hexagonals are acquired.Compared with traditional LCMLA with basic squared or circular microhole electrode,the light energy and pixel utilization efficiency are increased of ?15%.Secondly,the light field imaging calibration approach based on the dense arranging hexagonals and then a 3D measurement method are proposed.Through analyzing the light path allocation based on the LC-based plenoptic imaging principle,the 3D spatial mapping relationship of the raw lightfield images is given,and then the coordinate projection from the rendering images to the raw lightfield images is inferred,and thus the lightfield image rendering method based on the selected target plane is established.Compared with current lightfield rendering method based on sub-image stitching,the mismatches at the edge of the sub-aperture can be effectively eliminated so as to significantly improve the sharpness and the smoothness of the rendering image.The proposed rendering method demonstrate several characteristics including the wonderful real-time lightfield imaging and then millisecond/sub-millisecond time consume for per frame imaging.Finally,a passive autofocusing method based on the object spatial tomographic imaging is given to the mismatching between the driving and adjusting signals applied over the LC-based plenoptic imaging system corresponding to the multi-objects in complex environment.The association character between the image parallax and the driving and adjusting signals is experimentally evaluated,and also the mapping relationship of the parallax error testing and the autofocusing signal applied over the LCMLA is calibrated.Based on the 3D lightfield passive autofocusing method established,the driving and adjusting signal of the LCMLA can be adjusted automatically.According to the characteristics of the 3D lightfield image process and the tomographic imaging autofocusing acquired,an integrating development idea according to the embedded heterogeneous computing for the LC-based plenoptic imaging is proposed.