| Over a long term great efforts have been devoted to developing three-dimensional (3D) display. A great deal of researches have been carried out to investigate the methods and systems for 3D display, for this reason, rapid progress has been made in this area. Hitherto there exist many approaches to implement 3D display. Among them, holography is the only 3D imaging technique capable of recording and reconstructing genuine 3D image. However, conventional optical holography is considerably complex, time-consuming, and irreversible. Even after the realization of computer generated holography (CGH), we still need plotter or laser beam scanning recording device to make hologram with the results calculated from CGH, and reconstruct 3D image. In addition, real-time display has not been accomplished yet for a long period.For the past few years, with the development of semiconductor optoelectronic technology, computer generated holographic technique, spatial light modulator (SLM) and digital light processing (DLP), genuine 3D display becomes feasible.By combining SLM and the holographic technology, the present research proposes a method for reconstructing 3D image from kinoform with the use of two cascading liquid crystal spatial light modulators (LC-SLM), one of which is phase-only type and the other is amplitude type. The phase-only LC-SLM is used for displaying the kinoform and the amplitude LC-SLM is for amplitude information of the object. In this way,3D image reconstruction is achieved by diffracting the collimated light from the two LC-SLMs cascaded.This thesis is composed of three parts. In the first part, the history and the main developments of the 3D display techniques were reviewed, and then the present status of 3D display with spatial light modulator was introduced, as well as the basic theory of the kinoform.In the second part, including chapters 2 and 3, we introduced principles and applications of LC-SLM, especially, the characteristics of phase-only LC-SLM. After that, we measured its phase response curve. Furthermore, we analyzed the relationships between the parameters of LC-SLM, information quantity of kinoform, and the resolution of reconstructed image.In the third part, including chapters 4 and 5, we presented the experiment for reconstructing 3D image from kinoform with two LC-SLMs.3D objects such as Chinese character"光"and cubic framework were simulated with the use of computer software. The corresponding kinoform and the amplitude image of objects were calculated, respectively. The kinoform (phase information) was written to phase-only LC-SLM1, the amplitude image (amplitude information) was written to another LC-SLM2 operated in amplitude modulation mode, and the kinoform was imaged on LC-SLM2 by the image Lens. When gray-scale kinoform and amplitude image of 3D object were illuminated by a parallel light, the image of the original 3D object could be reconstructed. The experimental results suggested that the proposed technique was feasible. Taking the advantage of the characteristic of real-time display of phase-only LC-SLM, a complex objects-Portrait was reconstructed by time-division multiplexing. The object was decomposed along the longitudinal direction into several sampling groups. The kinoforms of the packed sampling were calculated and then inputted to phase-only LC-SLM in sequence. Due to the time residual effects of human eyes, the corresponding image from the kinoforms could be reconstructed by the diffraction. Accordingly, the 3D image could be seen in free space.Finally, the experimental results were analyzed, and then the problems appearing in experiment were pointed out. In further, we proposed a scheme on how to improve the experiment. |
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