高分辨率多视点动态全息3D显示

High-Resolution Multiview Dynamic Holographic 3D Display

提出了一种高分辨率多视点动态全息3D显示方法,观看视点位置变化时,观看者能够看到连续变化的3D效果。在进行全息图计算时,首先根据针孔阵列投影模型,渲染3D动画中每一帧3D模型的光场图像序列;然后从已渲染的多组光场图像序列中抽取对应视角信息的光场图像进行融合,得到融合后的动态光场图像序列;在进行全息图编码时,以动态光场图像序列中的一帧图像作为物光振幅,以来自于针孔的发散球面波的相位作为物光相位,引入平面参考光进行编码,得到一个单元全息图。由于每个单元全息图的计算是相互独立的,因此在计算过程中使用并行加速计算,实现了尺寸为32 mm×32 mm、分辨率为100000 pixel×100000 pixel的高分辨率全息图,其光场图像融合和全息编码的时间仅需27 min。光学再现结果证明了该方法的可行性。所提出的高分辨率多视点动态全息3D显示方法在全息包装和3D广告等领域具有广泛的应用前景。

Objective Holographic 3 D display has gained considerable attention owing to its ability to completely reproduce the wavefront information of a 3 D scene.To reconstruct a real and virtual 3 D scene,computer-generated hologram(CGH)is found to be more flexible than optical holography.The CGH has two main branches,namely,the dynamic holography reconstructed by liquid crystals on silicon(LCoS)and the static high-resolution holography realized by photolithography.However,due to the large pixel size and low-resolution,dynamic holographic 3 D display based on LCoS can only achieve a small field of view and small display size,thus limiting its application.High-resolution CGH can be calculated and printed using photolithography and copied for mass production.However,the computational time is a big challenge.To overcome this challenge,holography is regarded as an information encoding method,which is employed to encode light-field images,thereby significantly reducing the calculation time.Moreover,highresolution holography can only reproduce a static 3 D image,indicating that the viewer can see the perspective information of the 3 D image from different angles,but with a static 3 D image.Thus,more vivid holographic 3 D display needs to be realized.In this study,multiview dynamic holographic 3 D display is proposed by coding the dynamic light-field images fused from multiple rendered light-field images via 3 D animation.In this new display,the viewer can see a 3 D dynamic image when the viewpoint changes.Methods In the hologram calculation,the sequence of the light-field image of each frame of the 3 D model in the 3 D animation was first rendered according to the pinhole array projection model.Then,the light-field images that correspond to the view angle information were extracted from the rendered multiple sets of light-field image sequences and fused to achieve the fused dynamic light-field image sequence.In the hologram coding,the frame of images in the dynamic light-field image sequence was taken as the object light amplitude,and the phase of the diverging spherical wave coming from the pinhole was taken as the object light phase.In addition,the plane reference light was used to obtain a unit hologram.Since the calculation of the dynamic light-field image and each unit hologram are independent of each other,we used parallel acceleration in the calculation process.Light-field image fusion and holographic coding of a high-resolution hologram with a size of 32 mm×32 mm and a resolution of100000 pixel×100000 pixel only took 27 min.Results and Discussion A 3 D model with a size of 18.8 mm×30 mm×17 mm containing 4.06×105 object points was employed for high-resolution hologram calculation.The distance between the 3 D model and the hologram plane was 17 mm,and the 3 D animation was rotated horizontally,including 50 frame.The 355×139×50 light-field images of the 3 D animation were first calculated,and the 355×139 dynamic light-field images fused from the rendered light-field images were then utilized for hologram calculation.The high-resolution hologram with a size of32 mm×32 mm and a resolution of 100000 pixel×100000 pixel is calculated and printed using our holographic output system.The dynamic light-field image fusion and hologram calculation only took 27 min.In the hologram reconstruction,a white LED light from a mobile phone was used to illuminate the hologram at the back of the hologram at a proper distance and illumination angle.A USB camera on a one-dimensional rail was used to take pictures of the hologram.When the camera was focused on the holographic plane,the holographic plane became clear,whereas the reproduced 3 D image became blurred.When the camera was focused only on the 3 D-reproduced image,the reproduced image became clear,whereas the holographic plane became blurred.This phenomenon indicates that the proposed display can realize the 3 D light-field reconstruction.By moving the camera,the reproduced images of the other two perspectives were taken.Based on the results,we can infer that the 3 D image actions are different in different perspectives.In the actual view,human eyes can see the continuously changing 3 D animation by changing the viewpoints.Conclusion High-resolution multiview dynamic holographic 3 D display is realized based on the direct coding of dynamic light-field images.To produce the dynamic light-field images from the 3 D animation,the mapping relationship between the viewpoints and the time sequence of 3 D animation is established.The proposed 3 D display is vivid with a dynamic 3 D display from different viewpoints.The calculation method is also found to be effective.Although the display is a monochromatic 3 D display,the color 3 D display can be achieved using the combination of the color rainbow holographic method and the proposed method here.This will be the focus of our future work.Moreover,a large hologram can be produced for a more complex 3 D animation to improve the practicality of the proposed method.