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.