Three dimensional real image display with conical holographic stereograms

由于全息立体图能够再现计算机生成的三维图像，人们对其进行了大量的研究。其中，锥面全息立体图是最有趣的方法之一，因为它具有以下优点：可以方便地在全息面上再现浮动图像，并且可以从上倾斜方向观察图像。研究结果表明：(1)锥面全息立体图中，由于像的模糊程度与像到全息平面的距离成正比，所以图像的模糊程度往往较大。为了补偿这种模糊，提出了一种新的用于重建的照明光学系统。在这种方法中，全息图被与全息图具有相同平均空间频率的光栅的衍射光照射。(2)为了快速制作全息图，使用液晶空间光调制器(LC-SLM)来记录全息图，而不是使用不同视角的照相透明片。分析了LC-SLM和全息图的显示质量。(3)作为制作彩色全息图的基础研究，测量了三种波长的布拉格光栅的光谱衍射效率。为了制作彩色全息立体图，提出了一种利用三种不同的激光和一台彩色LC-SLM制作彩色全息立体图的光学装置。

Many types of holographic stereograms have been studied due to their ability of reconstructing three dimensional images made by computers. Among then, the conical holographic stereogram is one of the most interesting methods because of the following advantages ; the facility of reconstructing floating images above the hologram surface and the possibility of observing images from the upper inclined direction. The following results are obtained in this research.(1) Since the image blur is in proportion to the distance between the image and the hologram plane, the blur tends to be large in conical holographic stereograms. To compensate this blur, a new illumination optics for reconstruction is proposed. In this method, the hologram is illuminated by the diffracted light of a grating with the same average spatial frequency as the hologram(2) To make the hologram quickly, a liquid crystal spatial light modulator(LC-SLM)is employed to record the hologram, instead of photographic transparencies with different perspectives. It is analyzed that the quality of images displayed by the LC-SLM and by the hologram.(3) As a basic study of making color holograms, it is measured spectral diffraction efficiencies of Bragg gratings made with three wavelengths. In order to make a color holographic stereogram, an optical setup is proposed by using three different laser lights and a color LC-SLM.