基于小目标可见度STV的LED路灯视觉研究

【作者】 李福生；

【导师】 陈大华；

【作者基本信息】 复旦大学 ， 物理电子学， 2011， 博士

【摘要】 本论文主要是基于小目标可见度概念,研究LED在道路照明中应用基础。本论文主要内容是：首先进行了基于单色光小目标可见度视觉实验,并在此基础上建立了阈值亮度差光源光谱模型；然后以钠灯与LED为背景光,进行小目标可见度视觉比较实验和现场视觉评价实验；并根据道路照明小目标可见度标准,进行LED自由曲面反射器光学设计。在大量调研光源小目标可见度和LED道路照明国内外研究成果的基础上,提出采用投影法进行小目标可见度视觉实验。小目标可见度实验与其它视觉实验的主要不同点是小目标可见度要求视觉目标持续时间为0.2s,也就是视觉目标出现0.2s后消失。以前实验大都采用较长时间的刺激或静态刺激。投影法小目标可见度实验解决了观测时间和位置移动难题。投影法实验是通过电脑软件编程控制视觉目标持续时间、出现时间、对比度、背景亮度、背景光谱等参数,记录受测人员的反应,从而研究这些参数对小目标可见度影响。投影法更符合小目标可见度标准,也符合道路照明中,驾驶员视觉的真实情况。本论文进行了两个实验室小目标可见度视觉实验。首先利用窄带滤色片与投影仪组合,在屏幕上形成单色视觉目标和背景,研究探测几率和反应时间受背景亮度、对比度、背景光谱等参数的影响。利用上述单色光谱视觉功效实验与中间视觉理论,提出小目标可见度阈值亮度差光源光谱模型,并采用此模型对钠灯和LED灯具视觉实验进行修正,结果表明此模型可以修正光源光谱对小目标可见度的影响。根据道路照明亮度标准和小目标可见度标准,利用非成像光学理论进行了自由曲面反射器设计。首先根据非成像理论建立了反射器自由曲面的偏微分方程组,由于方程组比较复杂,将矢量偏微分方程组简化并代入柱面极坐标进行数值求解。将方程数值解导入3D软件生成自由曲面,并将其导入到光学软件进行光学模拟。本论文在上述实验室视觉实验的基础上,进行了小目标可见度场地实验。实验将钠灯和LED灯具照明效果进行比较。实验采用灰色和彩色视觉目标,由观测者观察视觉目标并做出视觉效果评价,从而比较光源光谱对小目标可见度的影响。实验得到钠灯和LED灯具灰色视标视觉评价值与小目标可见度关系曲线,并对两种光源对灰色和彩色视标可见度的影响进行了比较。论文的创新之处在于：1)提出阈值亮度差光源光谱(TLLS)模型,采用单色光的反应实验将中间视觉与小目标可见度相关联后,使小目标可见度能够更准确的适用于各种道路照明光源。2)设计了小目标可见度标准的自由曲面反射器,利用非成像光学理论,进行LED自由曲面反射器设计,反射器在达到基本亮度均匀度的基础上,大大提高了道路上面物体的可见度。3)采用实验室与道路场地两种实验方法进行LED与钠灯道路照明效果对比实验。其中场地实验采用IESNA道路照明标准灰色视标和彩色视标,对LED和钠灯道路进行现场视觉效果实验,并分别得到钠灯和LED灯具视觉评价与小目标可见度水平关系曲线。更多还原

【Abstract】 The principal purpose of roadway lighting is to produce quick, accurate, and comfortable visibility at night. Usually the truth that night accident rates would decrease and nighttime driver performance would increase with increasing light levels is accepted. This truth is now confronted now, and small target visibility (STV) is more suitable for roadway lighting.A STV experimental was designed, which parameters, such as back ground luminance, contrast, spectrum, duration of target are controlled by computer. With the aid of filter, five monochromatic lights were produced. And the reaction time which are influenced by the spectrum of these lights are record and analyzed. Based on the results of this visual performance experiments, a model for the calculation of threshold luminance was established, which can predict the influence of the relative spectral power distributions of light on the STV. More than that, a similar projector experiment was designed. In this experiment, the background of STV were light by LEDs and HPS, and the reaction time of subject were record and analyzed, then the comparison between LEDs and HPS is made. The result shows that targets are more visible under LEDs illumination conditions than under HPS illumination conditions despite the visibility levels of the small targets are all the same.Now LED has been widely used in roadway lighting because of characteristics such as high efficacy, long life and white light. Because of its luminous distribution is different from other light sources, optic design should be applied to the LED. Different with imaging optics, illumination optics belongs to nonimaging optics. Base on the standard of STV, a new method to design free form reflector was introduced.An in situ field study was conducted to examine the effect of SPD on the ability of detection of small object on the road surface, which it crucial for the safety of the drivers. Comparison between subjective rating in the case of fixed road lighting installation with LEDs and those in the case of HPS lamps was made by using visual experimental data and computer programs. And visual experiments with colored targets were also conduced to study the effect of color on the detection of small object under the road lighting conditions lit by LEDs and HPS lamps.The results of this comparative study show that achromatic and colored targets are a little more visible under LEDs illumination conditions than under HPS illumination conditions despite the visibility levels of the targets are all the same. The LEDs in our study have positive influence on visibility under road lighting conditions, but it is difficult to guarantee the influence is positive because of the diversity SPD of LEDs. The results also suggest if the road is lit by LEDs, colors have an effect on the visibility of object on road surface. This is very important, since color difference will play a prominent role on the detection of hazard object,when the difference between luminance of object and road surface is small,.更多还原