利用時間多工降低光斑實現彩色全像抬頭顯示器

Reducing Impacts of Speckle on Color Holographic Head-up Display by Time-Division Multiplexing Method

林碩恩(Shuo-En Lin)

指導教授 ： 黃乙白 ； 黃柏蒼

國立交通大學/電機學院/電機學院電子與光電學程/碩士(2020年)

摘要

隨著科技的進展，顯示技術日漸成熟，多年前人們在科幻電影中才能看到的景象，已經一一地被實現在現實生活中。想要看到影像栩栩如生的在眼前呈現，甚至不用出門去電影院看立體電影，在家裡打開頭戴式顯示器，虛擬實境就如同親臨現場。
目前市面上最常接觸的3D影像種類如立體電影，頭戴式顯示器(head-mounted display)，甚至是光柵式裸眼顯示器(parallax barriers display)，都是利用雙眼的視差在空間中錯位，來達到立體成像的效果。然而這種方式有一個缺點，利用視差呈現立體影像會產生所謂的視覺輻輳 (Vergence Accommodation Conflict；VAC)，這是指雙眼對焦的焦點與實際呈現畫面的顯示器位置有所差異，這會導致部分使用者在體驗這類產品時會感到暈眩。
由於上述問題，在一些不允許暈眩現象產生的使用狀況如車用抬頭顯示器，利用全像投影來進行立體投射又開始被重視。全像投影是一個把光聚焦在半空中的技術，配合電腦生成全像片演算法，讓即時的路況資訊，可以立體地被呈現在駕駛者的面前，提供良好及時的警示與輔助作用。
本文目的為提供一個彩色的全像車用抬頭顯示器方案，內容包含兩種消除色差(Chromatic Aberration)的投影架構。另外針對全像投影常見的光斑問題，我們利用時間多工技術達到光斑補償，在對單張投影片的對比度提升上使用演算法的改進，進而達到最佳的彩色投影成果。

關鍵字

全像投影 ； 彩色全像投影 ； 時間多工 ； 光斑消除

並列摘要

With the rapid development of display technology, people could now have amazing experiences realizing those scenes that were only seen in sci-fi movies years ago. People don’t even need to go out for a movie but just turn on the head-mounted display, and there’s a whole new world waiting for you to explore further.
The most accessible stereoscopic display, such as 3D film, head-mounted display, and even parallax barriers display, are all utilizing binocular parallax to produce 3D perception. However, there’s a disadvantage as the so-called Vergence Accommodation Conflict (VAC), which means there would be distances between points that focused on the panel and the actual projected images, thus causes users to feel dizzy.
Due to the issues of VAC, people then start further developments toward the application of holographic display on HUD, for example, an automobile head-up display. This is to avoid danger during some specific circumstances. To be brief, the holographic display is a technology that can focus images in the mid-air. With the usage of computer-generated hologram (CGH) technology, real-time driving information can be projected in the mid-air as a 3D image, which provides drivers some timely warnings and safety support.
In this study, two structures of color holographic display are proposed for HUD. Those different structures provide two ways to eliminate chromatic aberration. On the other hand, the speckle issue is a common problem of holographic display. Part of the research would be focusing on utilizing time-division multiplexing (TDM) method to suppress speckle, also improving contrast with the computer-generated hologram algorithm in holographic display.

並列關鍵字

Hologram ； Color hologram ； TDM ； Reduce speckle

參考文獻

Reference

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[4] Che-Yung Shen. “Holographic Head-Up Display System with a Wide Depth Range Realized by Hybrid Superimposing Multi-Constraints Algorithm”, National Chiao Tung University, master thesis, June 2019.