點矩陣式LED交通標誌之光學元件設計與評估;Optical Lens Design and Evaluation of LED Traffic Signs of Dot Matrix Type

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題名:	點矩陣式LED交通標誌之光學元件設計與評估;Optical Lens Design and Evaluation of LED Traffic Signs of Dot Matrix Type
作者:	方俊皓;Fang, Jiun-Hau
貢獻者:	照明與顯示科技研究所
關鍵詞:	LED交通標誌;套件;背向照明;概化估計方程式;LED traffic signs;Lens;Backward lighting;Generalized estimating equation
日期:	2019-08-12
上傳時間:	2019-09-03 15:26:25 (UTC+8)
出版者:	國立中央大學
摘要:	現今LED技術日新月異，在生活中各處皆可見到LED產品的應用，LED的低耗電、高流明、使用壽命長等優點使得LED儼然成為照明等相關應用的主流，在交通標誌上也是如此，為了增加夜間行駛的安全性，LED交通標誌也在逐漸增加，但LED標誌優劣仍是需要評估的。在先前研究之四種LED交通標誌結果中，針對各個標誌進行了舒適度、判別度與喜好度三個面向進行主觀感受問卷分析，但分析數據僅在各個面向獨立比較，而本研究利用概化估計方程式，將此三種面向的數據同時納入考量計算出一整合三者之邊際均值作為評估之綜合得分，隨後以各個LED交通標誌進行事後成對比較，其比較結果與先前研究結果相似，且利用這種估計方法可得單一得分作為指標，能更直觀的評估LED交通標誌不同設計的優劣，後續相關實驗可改採用此種方式進行評估。　　同時本研究針對先前研究所設計可用於點矩陣式LED的部份背向照明反射套件進行修正與人因實驗分析評估。先前研究中所設計之11種反射套件最後評估可使用之套件有兩種，本次選用的套件為薄塑膠套管，在一端鍍上90%高反射率鍍膜，背向反射照明分布為一環狀。在該研究中設計時僅考慮砲彈型LED而設計，但在實際應用上LED為了防水防塵需求會在外層額外增加ㄧSilicone防水層，使得LED尺寸增大，套件也因此較原先設計的大，增加了背向反射的範圍，而同時套件也為了耐用因素考量由壓克力改為聚碳酸酯，由以上因素影響使得背向反射光線範圍增加但強度下降，向前向後之光強度比為10.38:1，雖與原先預期有所差異但仍在可接受範圍。　　後續實驗分別對75公尺與30公尺的觀測距離對交通標誌看板各個部位的舒適度、判別度、喜好度進行評估後分析，其實驗所得數據由前段所述之概化估計方程式的方法進行綜合得分的計算與針對套件裝設有無進行事後成對比較，比較的方法以萬里兩字、單獨萬字、單獨里字等三個方式去評估套件的裝設成效，實驗數據雖在75公尺時有些許實驗上誤差，但在實驗結果上顯示該反射套件對於點矩陣式LED的觀看感受改善上並無幫助，後續實驗仍可改選用另一種反射套件並就反射光強及範圍進行修正後，嘗試得到預期的設計效果。 ;LED technology is changing with each passing day. LEDs have been widely used in lighting applications, including traffic signs. In order to improve the safety of night driving, more and more traffic signs have utilized LEDs. But these traffic signs need to be evaluated. Our previous studies have evaluated four custom-made LED highway traffic signs with different designs in three aspects, including the legibility, visual comfort and preferences. Each aspect was evaluated independently at the time. The current study uses the generalized estimating equations to calculate the marginal mean as the evaluation score for each sign’s messages when legibility, visual comfort and preferences across all signs are controlled. 　　The other study in this thesis is modifying the lens design with partial backward lighting in our previous studies to be used on LED traffic signs of dot matrix type. We designed a total of 11 lenses back then, and among them two lenses were more effective and applicable. The lens that we selected for the ergonomic experiment is based on a thin plastic sleeve with one end coated with 90 % highly reflective coating. The lens was designed to be fitted on bullet-shaped LEDs, but the LEDs used on the signs have silicone on the outer layer for waterproof and dustproof. So the lens is larger than the original design. In order to be durable, the lens material is changed from acrylic to polycarbonate. The influence of the above factors increases the illumination area of the backward light, and the intensity decreases. As a result, the power ratio of front-facing light to backward light is 10.38:1, which is still within the acceptable range although it is different from the original expectation. 　　The ergonomic experiments evaluate the legibility, visual comfort and preferences of each part of the traffic sign at the distance of 75 m and 30 m. The experimental data are estimated by the method of generalized estimation equations described in the previous paragraph. Then the pairwise comparisons on the mean evaluation scores are tested in three ways, including the data of Wan word, Li word and both of them. The results show that the lens with partial backward lighting has no benefit in improving the visual quality of LED traffic signs of the dot matrix type. Nevertheless, future experiments can still try some other lenses and tune the optical design to control the illumination area and intensity of backward lighting, in order to achieve better visual quality of LED traffic signs of dot matrix type.
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