Three dimensional real image display with conical holographic stereograms

由于全息立体图具有计算机再现三维图像的能力，人们研究了多种类型的全息立体图。其中，圆锥全息立体图是最有趣的方法之一，因为以下优点：再现浮在全息图表面上方的图像的设施和从上倾斜方向观察图像的可能性。本研究取得了以下成果。(1)由于图像模糊与图像和全息平面之间的距离成比例，因此在圆锥全息立体图中，模糊趋于大。为了补偿这种模糊，提出了一种新的照明光学重建。（2）为了快速地制作全息图，采用液晶空间光调制器（LC-SLM）代替不同视角的照相全息图来记录全息图。分析了液晶空间光调制器和全息图显示图像的质量。(3)作为制作彩色全息图的基础研究，测量了三种波长制作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彩色液晶空间光调制器的光学系统。

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.