三维物体空间再现技术中的全息图计算

全息空间再现技术可以记录三维(3D)物体并在空间重构出三维像，是真实地再现三维场景的一种新的可行方法。三维物体全息图的计算是全息空间再现技术中的关键技术之一。本文在简要论述三维物体计算全息技术的理论基础上，对具有代表性的三维物体全息计算方法的原理和技术要点进行了重点论述。采用了层析法、菲涅耳波带法、多视角投影合成全息法等三种方法进行了三维物体全息图的计算，并利用LCR-2500空间光调制器及650 nm的150 mW半导体激光器对层析法计算的三维物体全息图进行了光电再现，对其它两种方法获得的三维物体全息图进行了数值再现，并三种计算方法各自的特点和局限性进行了具体的分析。在对目前三维物体计算全息技术中存在的硬件和算法等关键问题进行分析的基础上，讨论了提高三维物体计算全息图的效率和质量的有效途径。

Computer-generated holograms calculation for spatial display of three-dimensional objects

Holographic spatial reconstruction technique is an important approach to display three-dimensional(3D) images because the amplitude and the phase of object wave can be recorded in a single hologram, and then 3D image can be reconstructed in free space. Hologram calculation of three-dimensional objects is a key part of holographic spatial reconstruction technique. The basic theories for computer-generated hologram(CGH) calculation of 3D objects were described firstly. Then the principles and key techniques of several typical approaches for CGH calculation of 3D objects were analyzed. Three types of CGHs were calculated for 3D objects by use of tomography approach, Fresnel zone approach and multi-view image synthesizing approach. Subsequently, electro-holographic display experiment was performed by inputting CGH of 3D object calculated by tomography approach into LCR-2500 spatial light modulator and using diode laser with wavelength 650 nm and power 150 mW. Numerical reconstruction results were also obtained from the CGHs calculated by other two approaches. Then the characteristics and limitations were analyzed for the existing methods of three-dimensional CGH calculation. Some key problems associated with hardware and algorithms were also analyzed, and the approaches were discussed for improving the calculation efficiency and the quality of CGH.