| Integral imaging, as a novel3D imaging and display technique, first proposed by Lippmann in1908, has been resurrected and developed rapidly during these ten years. The principles of this technique can be divided into two parts:Recording3D scene and reconstruct3D scene. To record3D scene, the information of3D scene is recorded onto2D sensor by a micro lens array (MLA). To reconstruct3D scene, we just reverse the record process. There are lots of advantages of integral imaging technique. Compared with polarization and red-green3D display techniques, no glasses are required by integral imaging. Compared with grating and cylindrical lens array3D display technique, full parallax and quasi-continuous views angles can be display by integral imaging. Compared with holography3D display technique, no laser is needed during recording and reconstructing process by integral imaging. All in all, integral imaging is a novel3D technique with merits of viewed by naked eyes, no need of coherent light and displayed with full parallax views. However, every coins has two sides, integral imaging is not perfect. Two major drawbacks of this technique are poor lateral resolution and limited depth of field (DOF), which is either constrained by pixel of display, or limited by sizes of MLA, or both of them. Therefore, it is quite meaningful to improve the DOF and resolution of integral imaging.To contribute to this promising3D technique, we have put our effort into improving the DOF of integral imaging system during" last three years. This dissertation mainly focus on improve DOF of integral imaging system by wave coding technique. Designing new phase plate and concrete experiment are also included. The dissertation can be divided into the following six parts:Firstly, the principles of integral imaging are introduced and three main parameters (view angle, resolution and DOF) of integral imaging are analyzed. After most existent methods to extend DOF of integral imaging system are reviewed, we proposed a new method, which is using wavefront technique to enlarge DOF of integral imaging system. Secondly, we introduce the principles of wavefront coding technique and discuss several asymmetric phase plate used in wavefront coding system. Later, we reviewed all kinds of phase plate to extend DOF. And several continuous relief phase plates are fabricated by laser direct writer.Thirdly, a new method of generating high quality phase plate is proposed. By adding a conventional blazed grating onto a cubic phase plate, it enables elimination of direct incident illumination in the reconstructed beam. Experimentally measured intensity distribution of the blazed cubic plate is found in much better than traditional cubic phase plate.Fourthly, we demonstrate an experimental approach to enhancing DOF of the integral imaging system by using a coded camera array with a cubic phase plate (CPP). A7x7coded elemental image array is acquired by moving a single CPP coded camera placed on the electric translation stage for7x7times. The coded elemental images captured by the coded camera array have larger DOF than common camera array. After digital process of the coded elemental images, we obtained elemental images with enhanced DOF for3D display.Fifthly, we try to apply wavefront coding technique to integral imaging microscopy. We build the wavefront coding integral imaging system and choose hair of a man as a3D sample. After digital process of the coded elemental images, we obtained elemental images with a little enhanced DOF.Finally, an improved sinusoidal phase plate is proposed by adding a new parameter to a conventional sinusoidal phase plate. A series of performance comparisons are made among various phase plates including sinusoidal, cubic phase and the modified logarithmic phase. The results demonstrate that the improved sinusoidal phase plate can further extend the depth of field in incoherent hybrid imaging systems, with a lower surface relief phase structures fabricated in photoresist (AR-N4340, ALL Resist, Germany). |
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