Objects with extremely high brightness or strong contrast in the field of view may cause discomfort and cause a decrease in vision. This is glare, which can be divided into disability glare and discomfort glare. The glare that reduces the vision of the human eye is called disability glare. Any glare that makes people feel uncomfortable is called discomfort glare. Glare is one of the important factors affecting the quality of lighting.
2 The generation of glare glare is divided into direct and reflected glare. Direct glare is caused by an over-bright light source that appears in the observer's normal visual range. The reflected glare is caused by the observer's strong reflected light from the light source on the smooth surface.
The main factors that cause glare in road lighting: 1 the brightness of the light source (the higher the brightness, the more significant the glare); 2 the position of the light source (the closer the line of sight, the more significant the glare); the size and number of the light source (the larger the apparent area) The more the number of light sources, the more significant the glare is; the environment around 4 (the darker the ambient brightness, the lower the brightness of the eye, the more significant the glare).
3 glare analysis Nowadays, new road lighting projects in some cities tend to be better than climbing. In fact, not only is energy wasted, but it may also cause glare. China's urban road lighting design standards for brightness regulations are shown in Table 1. Table 1 other lj road type expressway trunk roads and Yingbin Road, roads leading to government agencies and large public buildings, downtown or commercial centers, large roads The secondary trunk roads such as transportation hubs are mainly used for pedestrians and non-motor vehicles. The average brightness of roads and sidewalks in residential areas is Note: The value in the table is the maintenance value, and the initial brightness value of road surface of newly installed light source lamps is increased by 30%~50%. In order to avoid glare, a semi-transparent diffusing plate should be used for the brightness of 20 light sources to improve the luminous surface of the lamp, reduce its brightness or use a combination of reflectors, grids or reflectors to block the light source lamps so that the light source cannot directly enter the human eye. For light sources with a brightness above 20 000 cd/m2, only the occlusion method can be used.
The degree of glare is also closely related to the position and angle of the illuminator relative to the eye. The smaller the angle, the stronger the glare phenomenon and the greater the illuminance loss.
The urban road lighting standard (CJJ45-91) is to reduce the glare and stipulate the expressway. The main road must adopt the cut-off type and half-cut type luminaire; the secondary trunk road should adopt the half-cut type luminaire, and the branch road should adopt the half-cut type luminaire. The elevation angle of the lamp arrangement should not exceed 15*; the maximum light intensity direction and vertical angle of the lamp should not exceed 653. In the past, there is often a misunderstanding in road lighting. It is believed that the more light sources and the larger the apparent area, the better the lighting effect. In fact, this It is only to meet the requirements of people's visual perception, and it does not have much benefit in improving the lighting effect. The increase of the luminous point and the increase of the luminous surface make the nightwalker's attention less concentrated, increasing the probability of glare and causing hidden dangers to safety. For this reason, in the three-dimensional cross lighting, it is not appropriate to set too many light source lamps, and high pole lighting should be preferred. Under the premise of meeting the functional requirements, it should be as beautiful as possible, and the function of road lighting should not be sacrificed for the pursuit of beauty. Nowadays, overpasses in some cities are often adorned with crystal clear lamps on the railings, but as a hub for urban transportation, overpasses are particularly limited to glare. Especially in the steep section of the bridge, avoid glare to the driver on the bridge; secondly, avoid glare to the driver on the road connected to it or on the adjacent road; the third is to cause glare to the vehicle or vessel under the bridge. If it is necessary to have decorative lighting, it is necessary to use lamps that are strictly light-controlled (such as special light barriers or grilles in the lamps).
The glare caused by the environment generally appears in the transition of light and dark environment such as tunnels in road lighting. There is an adaptation process from the bright environment to the dark environment or from the dark environment to the bright environment. The former is called dark adaptation, the latter is called adaptation, the dark adaptation is longer than the adaptation time, and the time and brightness required to adapt are poor. related. The main consideration in road lighting is dark adaptation. In order to avoid such glare, it is not suitable for the human body. Therefore, it is necessary to add transitional illumination from the section where the illuminator is installed to the section where the illumination is not provided. That is, the lighting section is extended and the lighting level is gradually lowered.
There are two main methods for glare evaluation from the perspective of road lighting technology. 1 brightness curve method: also known as brightness limit curve method, is an evaluation method of discomfort glare, is established in the experiment by a group of observers to evaluate the discomfort glare, and uses the evaluation value to describe the degree of glare feeling, Finally, the brightness limit curve is converted. °! Xuanguang index method: Although the brightness curve is an intuitive and easy glare evaluation method, it is difficult to take into account various factors in the light environment by the two sets of brightness limit curves, especially the brightness of the surrounding environment. The effect and the effect of multiple light sources on glare. The glare index method is a more accurate method for evaluating glare, but the calculation is more complicated and cumbersome. In the actual road lighting engineering design, the cooperation of lighting experts is required to calculate accurate data.
4 Conclusion Glare is not beneficial in road lighting. For example, in commercial streets, residential areas, pedestrian tunnels, pedestrian bridges and other places where motor vehicles are prohibited, glare can be used to create an atmosphere. A large number of incandescent lamps are placed in the space to sparkle, giving a gorgeous, joyful feeling; using high-brightness light sources to illuminate the reflectors such as glass to reflect people's eyes, some dazzling, but give a pleasant and exciting feeling. Therefore, glare is a hindrance to the visual or active atmosphere, and should be differentiated and utilized according to the different needs of different places.
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