基於高折射率差光柵之裸眼立體顯示

Abstract

裸眼立體顯示器是立體顯示技術中的一個分支，其不需要配戴眼鏡的優勢提 供了更廣泛的運用場景，然而市面上的兩種主流技術：視差屏障式(parallax barrier)與柱狀透鏡陣列式(lenticular)各自有著如低出光效率或高交互干擾且體積大等問題存在。2010 年，Chen等人提出利用以布拉茲光柵層為基礎的繞射式光學元件，有著高出光效率與輕量化等優勢，但因繞射元件存在色散效應會降低影像品質，雖然後續以三種不同週期的布拉茲光柵層作為解決方案，卻也同時提高了製程難度。 本論文以有限元素分析軟體模擬單層平面的次波長高折射率差光柵層作為液 晶架構下的奇偶次畫素分光結構，透過改變矩形介電質(TiO2 on glass substrates)的結構參數來操控入射光之相位，不僅可以精準的控制出光方向，同時因為其次波長的週期，只存在零階繞射，可以有效的避免其他繞射階造成的交互干擾。本研究也驗證了相較於主波長，光柵波長色散效應不會對影像品質造成影響，並證實此結構在臨界的背光源角度半高全寬為7度時，能夠創造觀賞者與螢幕距離間高達15cm符合交互干擾標準的自由移動範圍。

The autostereoscopic (AS3D) display is a promising research topic in 3D display technology due to the advantage of providing 3D perception to the viewer without needing to wear special viewing gear. However, among two mainstream AS3D systems, specifically parallax barrier method and lenticular method, some drawbacks are inevitable, such as lack of power efficiency for the parallax barrier method, and image cross-talk with bulky components for lenticular method. In 2010, Chen et al. proposed a revised method by replacing the optical components adhered in front of the display to diffractive blazed gratings, which are more power-efficient and compact. Still, it remains some challenges in the mass-production process. During the past few decades, the advances and the wider accessibility of nanofabrication technologies, dielectric high-index-contrast gratings (HCGs) have caused a surge with its’ outstanding optical performance. In this paper, we propose planer visible-light HCGs with beam steering ability for transmitted beam using titanium dioxide on glass substrates. By choosing proper grating parameters, we can manipulate the phase of incident light according to the design. Subwavelength-grating profiles result in highlydirectional far-field patterns, which decreased image cross-talk naturally. Also, we have verified that color dispersion has a minor effect on the overall image quality. With the threshold FWHM of the directional backlight at 7 degrees, a design based on iPhone XR which viewing distance ranging up to 15 cm meets cross-talk criterion was achieved by the simulation.