12 September 2013 High efficient polymer dispersed liquid crystal for ultra-bright projected image
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Head-up display (HUD) commonly uses liquid crystal to generate images. However, the intensity of the light decreases a lot because of passing through the polarizers. Therefore, polarizer-free display is a way to enhance the light efficiency. We demonstrate the feasibility of using Polymer Dispersed Liquid Crystal (PDLC), which consists of polymer and liquid crystal, as an optical switch to fabricate a simple see-through projected display device. Due to the unique E-O characteristics of PDLC, it can be a role to define the projected image shape. In our device, we use the ultra-bright collimated LED as a backlight source so that the projected image can also be seen clearly in broad daylight. Besides, PDLC do not need to utilize polarizers. It is achieved to obtain very high light efficiency (~70%). In this paper, we show some results of projected images with various colors (RGB) that can be applied to see-through projected display. From our experiment result, the see-through projected display device by PDLC can achieve high contrast ratio (~1000:1) and response time is about 15~20 ms. The driving voltage is around 20~25 V. Further improvement can be achieved by optimizing the LC material/monomer concentration or others parameters.
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Shun-Ling Hou, Shun-Ling Hou, Wing-Kit Choi, Wing-Kit Choi, Guo-Dung Su, Guo-Dung Su, "High efficient polymer dispersed liquid crystal for ultra-bright projected image", Proc. SPIE 8828, Liquid Crystals XVII, 882816 (12 September 2013); doi: 10.1117/12.2023185; https://doi.org/10.1117/12.2023185

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