LED光源光谱对隧道出口段明适应的影响

Impact of the Spectra of LED Sources on the Light Adaptation in Tunnel Exit

随着我国经济的不断发展,高速公路隧道建设的发展也非常迅猛。前期在隧道的实际工程设计中,为完全保证隧道车辆通行安全,隧道内部全线灯具的输出功率和安装布置全部取决于一年四季中最大的洞外亮度值和车辆速度值。这样的设计尽管充分考虑了安全性,但盲目的增加隧道照明亮度,不能够缓解视觉适应的问题。随着LED在隧道照明中的应用, LED光源光谱的影响逐渐引起人们的关注。调查研究发现高速公路隧道在出口段交通事故发生率比较高,主要原因是隧道出口段内外亮度差较大,驾驶员在驶离时明适应时间较长。LED光源的光谱呈现双峰结构,在长波长范围内,光谱含量差异明显。明适应的能力主要与两个因素有关,一是瞳孔面积的变化;二是感光色素的光化学反应。不同色温的LED具有不同的光谱特性,进而通过影响感光色素的合成,来影响明适应的时间长短。现在市场上可用的隧道照明LED光源的色温可选范围比较广,所以实验选取了市场上可用的不同色温的大功率的LED光源作为研究对象,其色温分别是3 000, 3 500, 4 000, 4 500, 5 000, 5 700和6 500 K等7种。邀请了30名视觉功能正常,矫正视力1.0以上,且无色盲、色弱等其他眼疾的观察者参加了本次实验。地点选择在长9 m,高2.8 m,宽5 m的模拟隧道内。实验参数选取3组亮度值,分别为4, 8和12 cd·m^-2;2个灯具安装高度分别是2.0和2.4 m;3个安装角度分别是15°, 20°和25°。共评估了126种照明条件。实验结果表明:隧道出口段亮度越大,明适应时间越小;当亮度相同时,随着色温的增大,明适应时间减小;灯具安装角度和安装高度对光谱的影响很小,改变安装高度和安装角度并不能有效的减小明适应时间。从明适应的角度出发,通过分析不同色温LED灯的光谱,为隧道照明设计与应用中出口段LED光源的选择提供数据和理论支撑。

With the development of China’s economy, the development of highway tunnel construction is also rapidly. In the early stage of engineering design to ensure the safety of traffic in the tunnel, the power and location of the tunnel lighting sources all depend on the maximum outside luminance value and vehicle speed value through out the year. Although such a design considers safety, but it blindly increases the luminance of the tunnel illumination and it can not alleviate the problem of visual adaptation. However, with the application of LED in tunnels, the impact of LED sources spectra gradually attracted people’s attention. Moreover, the investigation found that the traffic accident rate of the highway tunnel in the exit section is relatively high. The main reason is that the luminance difference between the inside and outside of the tunnel is large, and the light adaptation time is long when the driver leavesthe tunnel exit. In order to study the impact of LED sources spectra on the light adaptation in tunnel exit, and to provide a basis for the selection of light source in tunnel exit, the LED source was characterized by a wide spectrum double-peak pattern. In the long wavelength range, the spectral content is different. The light adaptation is mainly related to two factors: the change of pupil area and photochemical reaction of the photopigment. LED light sources with different color temperatures have different spectral characteristics. The spectrum affects the time of light adaptation by affecting the synthesis of photopigment. The experiment selected 7 color temperature LED light sources used in the field of highway tunnel. The color temperatures are: 3 000, 3 500, 4 000, 4 500, 5 000, 5 700 and 6 500 K. Thirty observers were chosen for the experiment. All observers had normal visual corrected visual acuity. None of the observers had night blindness, color blindness or other diseases affecting night vision functions. The experiment was carried out in a simulated tunnel with a height of 2.8 m, length of 9 m and width of 5 m. Three photopic luminance levels for the experimental LEDs(4, 8 and 12 cd·m^-2), three illumination angles(15°, 20° and 25°) and two mounting heights(2.0, 2.4 m) were applied. In total, 126 lighting conditions were evaluated in the experiment. The results show that the higher luminance of the tunnel exit section, the shorter light adaptation times. When the luminance is the same, as the correlated color temperature increases, the light adaptation times decrease. The installation angle and height of the lamps have little effect on the sources spectra. Changing the installation height and angle can not effectively reduce the light adaptation time. This paper provides data and theoretical support for the selection of the color temperature in the exit section by analyzing the spectrum of LED sources with different color temperatures.