Auxiliary Resonant Scanner to Increase the Scanning Capability for Coarse Integral Holographic Displays

Schematic of the scanned holographic display system. (a) The two-stage scanning structure, which has one resonant scanner and one 2-axis galvanometer scanner. (b) The sub-vertical dither scan pattern. By taking advantage of the high scanning ability of the auxiliary scanner, the overall visual extent of the system is able to be expanded by multiple times.

The light propagation reconstruction feature supported by holography can provide all necessary 3D visual information, in theory. Therefore, holographic display has been considered as the promising candidate of the futuristic 3D image display for decades since the image hologram was realized.

However, there are some constraints limiting the applications of 3D holographic display technique. One of the major challenges to realizing a holographic display is to provide sufficient distribution capabilities for the high amount of optical information from spatial light modulators (SLMs). Nowadays a single SLM can achieve the rate of more than 10 Gpixels/s, nevertheless, all this information needs to be evenly distributed in space to tile up the targeted visual scope (image size and viewing angle). Scanning this information by a galvanometer (rotating mirror), however, is limited by the mechanical limitation, and this method doesn't support to distribute the information at the rate of 10 Gpixels/s or more.

To deal with this difficulty, the research team led by Prof. Daping Chu has proposed a scanned holographic display system which takes advantage of a high-speed resonant scanner to augment a galvanometer and hence improves the opto-mechanical information distribution capabilities, thereby potentially achieving the increased image sizes and the enlarged viewing angles. This work is published in Chinese Optics Letters, Volume 15, No. 4, 2017 (Jhen-Si Chen, et al., Auxiliary Resonant Scanner to Increase the Scanning Capability for Coarse Integral Holographic Displays).

In the proposed scheme, a resonant scanner is combined with a 2-axis galvanometer, to introduce another sub-dimensional scanning. It takes advantage of the high speed of the resonant scanner (because of the small mirror) to scan information into a larger but still small area before the galvanometer further distributes this information to a larger area.

This two-stage scanning structure fully utilizes the scanning capability of the two kinds of scanners and shows its potential to support distributing information rate of 50 Gpixels/s. The present work will play an essential role in the investigation of the coarse integral holographic video displays for achieving the target of a full-bandwidth, large image size and field of view (FOV).

Further work will focus on developing scalable, tile-able, and integrated coarse integral holographic video display systems by using the auxiliary resonant scanner, and approaching the challenges of applying these techniques to different 3D holographic displays systems.




然而,全息显示技术实现应用也面临着一些需要克服的障碍。主要挑战之一便是如何分配来自空间光调制器的大量光信息。当前单个空间光调制器能达到高于10 G 像素每秒的信息率,但所有这些信息需要在空间上均匀地分布,以便根据图像尺寸和视场角拼接成目标视觉范围。通过电流计扫描振镜来传递这些信息受到其自身机械性能的限制,无法满足每秒分配10 G像素或更高速率的信息量的要求。

为了克服这个困难,剑桥大学初大平教授课题组提出了一种扫描式全息显示系统的方案。该方案利用一种共振扫描振镜,与电流计扫描振镜实现互补,从而提高了信息分配能力,满足了大图像尺寸和广视场角的需求。相关研究成果发表在Chinese Optics Letters 2017年第4期上(Jhen-Si Chen, et al., Auxiliary Resonant Scanner to Increase the Scanning Capability for Coarse Integral Holographic Displays)。


利用这种两级扫描结构,可以充分发挥两种扫描振镜各自的优势——共振扫描振镜的高扫描速率和电流计扫描振镜的大扫描镜面,进而有效实现信息的分配。实验结果表明这种方法具有高达每秒分配50 G 像素信息量的潜力。这项工作对于以大图像尺寸、广视场角和全带宽为需求进行疏积分全息显示的研究有着极为重要的价值。