利用微光學元件及繞射分析提升有機發光二極體顯示器之環境對比度與穿透影像品質

Abstract

有機發光二極體顯示器(OLED)相比目前主流的液晶顯示器，擁有大視角、高對比度、低功耗、具可撓性以及可透明顯示等特性，是次世代顯示主流技術。然而，OLED畫素金屬陰極的高反射率除了有效的回收背向顯示光源外，卻也大量的反射環境光，造成OLED顯示器環境對比度不佳的問題，目前業界使用圓形偏光片消除環境光反射，但OLED有效光亦有極大損失，且偏光片可撓性不佳；而在透明OLED顯示器的應用中，穿透影像品質不佳的現象嚴重影響了觀賞體驗，目前還沒有研究指出穿透影像模糊的成因，亦沒有研究針對穿透影像的模糊化問題做出最佳化設計。 為了解決環境對比度不佳的問題，本論文首先設計了微光學元件，利用微透鏡陣列和非均勻分佈的黑色畫素陣列破壞了環境光反射進入使用者眼睛的光路。微光學元件可以吸收96.25%的環境光、維持95.09%開口率，而且微光學元件厚度只有50.9μm，可撓性佳。本論文還利用等比例實驗模型驗證了設計結果。而在透明顯示的部分，為了解決穿透影像品質不佳的問題，本論文指出繞射是造成模糊化最主要的因素，並且根據觀賞者與背景位置，定量修正了Fraunhofer繞射計算，提出了系統性的穿透影像計算方法。計算的穿透影像與實驗結果比對，誤差只有5.6%。基於提出的計算方法，本論文還設計了新的透明顯示器畫素結構，透過計算與實驗，找到了優於傳統透明顯示器的開口設計。本論文在最後提出兩種機制的合併，以達到高環境對比度與俱備清晰的穿透影像之透明OLED顯示器。

Compared to the current mainstream liquid crystal display, organic light-emitting diodes (OLED) display has wide viewing angle, high contrast, low power consumption and it can apply for flexible and transparent display. However, the metal cathode with high reflectance in an OLED pixel not only recycles display’s effective light, but also reflects ambient light strongly, which makes OLED display to have poor ambient contrast ratio. To solve this problem, circular polarizer is widely used in current products to eliminate ambient light reflection, but it also reduces display’s effective light and has poor flexibility. On the other hand, in the application of transparent display, poor see-through image quality seriously degrades the viewing experience. However, there has been little research that indicates the reason of image blurring or optimizes OLED pixel structure for better see-through image quality. To solve poor ambient contrast ratio of OLED display, this thesis designs micro-optical components, in which micro-lens array and non-uniformly distributing black matrices can block the light path for ambient light to propagate from the ambience to user's eyes. Designed components can absorb 96.25% of ambient light reflection while maintain a high aperture ratio of cathode layer of 95.09%. Moreover, the thickness is only 50.9μm, hence it can adapt to flexible display. Additionally, this thesis also succeeds to verify the design results by using proportional experimental model. On the other hand, to solve the problem of poor see-through image quality of transparent OLED display, this thesis points out that diffraction is the main factor that causes image blurring. By accurately correcting Fraunhofer diffraction according to the viewer and background distances, a systematic method was proposed to calculate see-through image quantitatively. The error between calculated and actually captured see-through images is only 5.6%. Based on the calculation method, this thesis also optimizes transparent OLED pixel structure and achieves significantly higher see-through image quality. By combining these two studies, OLED display can achieve higher ambient contrast ratio and clearer see-through image.