The light color of the light source includes color rendering and color temperature. Visual function is the ability of a person to complete a certain visual operation with the aid of a visual organ. The visual effect is usually assessed by the speed and accuracy of the completed work. In addition to the human factor, it is closely related to the illumination. Within a certain range, with the improvement of the illumination, The visual effects will be significantly improved.
At present, the tunnel lighting design codes and standards of the EU  and CIE [2-3] only consider the brightness or illuminance level of the tunnel pavement, and the effects on the visual effects such as color temperature, color rendering and spectral distribution are insufficient. The evaluation of tunnel lighting quality is not scientific enough, resulting in traffic safety and energy waste. With the improvement of the functions of instruments and equipment and the development of research methods, more and more researchers are paying attention to the influence of light source color on the visual efficacy of drivers . Liu Yingying et al  will be different through reaction time and pupil experiment. A variety of light sources of color temperature were introduced into the tunnel illumination sections and corresponding research was carried out. The relationship between the color temperature of the light source and the reaction time and the size of the pupil of the human eye was obtained, and the light source suitable for the illumination of the tunnel transition section was found. Zhang Qingwen et al  used the visual effect method to measure the visual effect of the human eye under different color temperature LED light sources by using the “reaction time measurement system”, and obtained the color temperature value of the LED light source suitable for road illumination and applied it in practice. Chen Zhonglin et al  studied the luminous efficiency of high pressure sodium lamp and metal halide lamp under different brightness conditions based on Sichen visual theory and intermediate vision theory. The reaction time experiment was carried out and the Sichen vision of metal halide lamp was obtained. The conclusion that the luminous efficiency is higher than that of the high-pressure sodium lamp under road illumination is worthy of tunnel lighting. Hong Weipeng et al  selected five background brightnesses under bright vision and intermediate vision conditions to test the reaction time of 10 visually normal testers, and studied high pressure sodium lamps, metal halide lamps, compact fluorescent lamps and LEDs. The light effect of 4 kinds of light sources. Using the test results of the reaction time, the suitability and energy saving of different light sources in the tunnel lighting environment were determined. Cui Wei et al  studied the relationship between the color of the tunnel illumination source and the visibility of the small target, and proposed a visual experiment method for the small target color rendering, which opened up a new idea for studying the small target visibility of tunnel illumination. Barbur et al.  proposed the theory of change of visual vision, dark vision and intermediate vision in visual effects. This theory provides a research method and a certain theoretical basis for the study of tunnel illumination. Miomir Kostic et al.  used intermediate vision theory to compare the different cases of applying HPS light source and MH light source in tunnels, pointing out that although HPS has higher color rendering and better color appearance, MH light source is more practical and energy-saving. Should be promoted in tunnel lighting.
The author studies the influence of the light color of the tunnel illumination source on the driver’s visual effect through experiments to obtain the relationship between color rendering and visual effects, as well as the color temperature of the light source, the relationship between the target color and the visual effect.
1The effect of color rendering index on driver’s visual efficacy
1.1 The effect of color rendering index on driver’s vision
The effect of the color rendering index of the tunnel illumination source on the visual performance of the driver was studied through field experiments. Two tunnels were selected for small target recognition experiments. The two tunnels were marked as No. 1 tunnel and No. 2 tunnel. The light source used in No. 1 tunnel was HPS and HPS and LED were installed. One of the light sources is turned on as needed during the process. The basic parameters of the two tunnel illumination sources are shown in Table 1.
The experiment selected three neutral colors (white, gray, black) and four color (red, yellow, blue and green) cubes (20cm × 20cm × 20cm) as the recognition target, and placed the recognition target in the tunnel. On the road, let the 10 testers identify the target from the observation points of the distance recognition target 40, 50, 60, 80, 110m, and answer the following questions: 1) whether there is a target; 2) if there is a target, the target What color is it. Figure 1 is a schematic diagram of the experimental arrangement.
1.2 Analysis of experimental results of the influence of color rendering index on driver’s visual efficacy
The experimental results show that in the observation point with the observation distance of 110m, the correct recognition rate of the small target in the tunnel No. 1 (in this case, the identification of the target object) is 69%, and the correct recognition rate of the No. 2 tunnel with LED illumination is 86. %, the correct recognition rate of the No. 2 tunnel with HPS illumination is 77%; at the observation point with the observation distance of 80m, the correct recognition rate of the small target in the No. 1 tunnel is 77%, and the correct recognition rate of the No. 2 tunnel with LED illumination For 90%, the No. 2 tunnel is 80% when illuminated with HPS. The experimental results are shown in Figure 2.
It can be seen from Fig. 1 that, under other conditions, the higher the color rendering index of the tunnel illumination source, the more favorable the driver’s recognition of obstacles is, which is beneficial to driving safety and lighting energy saving. However, there is no research result on the relationship between the illumination provided by the light source with different color rendering index when the correct recognition rate of the small target is the same. The tunnel lighting design should meet the requirements for light source color rendering. It can be implemented in accordance with the relevant provisions of the Industrial Enterprise Lighting Design Standard (GB 50034-1992). According to the provisions of Article 6.2.3 of the standard, in the workplace where color recognition is required, when the illumination intensity is 500lx or less and the color rendering index of the light source is low, the illumination standard value should be increased, and the improvement value is The illuminance standard value is multiplied by the phase contrast coefficient value in Table 2.
Effect of 2 color temperature on driver’s visual effect
2.1 Tunnel lighting source color temperature impact on the driver’s visual experiment
In order to study the situation that the driver’s visual effect is affected by the color temperature of the tunnel illumination source, the “tunnel illumination reaction time measuring device” is used in the laboratory to simulate the condition of the tunnel illumination, and the test driver simulates the background brightness levels provided by different color temperature sources. Reaction time. The “tunnel illumination reaction time measuring device” consists of four parts: the observation box, the optical system, the light box, and the electronic chronograph. The experimental setup is shown in Figure 3.
In order to study the effect of light source color temperature on vision, two compact fluorescent lamps with color temperatures of 2 700K and 6 400K were selected for reaction time comparison experiments. In the experiment, two kinds of fluorescent lamps were used to provide background brightness of 1.0~4.0cd/m2, and the randomly appearing spots were used to simulate obstacles that may appear in the tunnel. The spot diameter is 26mm, and the relative eyes of the subject are 2° field of view. The brightness of the target can be adjusted as needed to form a different brightness contrast with the background. The color of the spot is changed by adding a filter to make the colors red, yellow, blue and green. The tester responds the fastest to the appearance of the optotype under specific visual conditions and records the reaction time by an electronic timer through a button.
2.2 Analysis of experimental results of color temperature on driver’s visual effects
Under the different background brightness provided by the two light sources, the average time of the tester’s reaction time for different color spots is shown in Fig. 4. As can be seen from Fig. 4, under the tunnel illumination condition, when the color temperature of the compact fluorescent lamp is 6 400K, The tester’s reaction time was relatively short; when the color temperature of the compact fluorescent lamp was 2 700 K, the tester’s reaction time was relatively long.
When the target spot color is different, the relationship between the tester’s reaction time and the background brightness is generally similar. The tester’s reaction time is shorter as the background brightness increases, and the background brightness is the same. The reaction time under the compact fluorescent lamp with high color temperature is shorter than that under the compact fluorescent lamp with low color temperature, as shown in Fig. 5. However, for the target spot of four different colors of red, yellow, blue and green. When the background brightness is the same, the tester’s reaction time difference between the two color temperature light sources is significantly different. It can be seen from Fig. 5 that for the blue target spot, when the background brightness is the same, the difference between the reaction time of the tester under a compact fluorescent lamp with a color temperature of 6 400 K and the reaction time of a compact fluorescent lamp with a color temperature of 2 700 K is compared. Large, and for yellow and green target spots, the difference in reaction time is small. This shows that for practical color tunnel lighting applications, if the reaction time is used as an evaluation index, a compact fluorescent lamp with a high color temperature is better than a compact fluorescent lamp with a low color temperature. If you consider the color of obstacles that may appear on the road, when the color of the obstacle is rich in short-wave components in visible light, the illumination effect of the high-color illumination source is more obvious.
The reaction time experiment results show that under different lighting environment experimental conditions (background brightness, visual eccentric angle, visual standard contrast), the driver has four colors of red, yellow, blue and green under a compact fluorescent lamp with a color temperature of 6 400K. The reaction time of the target spot is shorter than that of a compact fluorescent lamp with a color temperature of 2 700K. By analyzing the spectral composition of these two different color temperature compact fluorescent lamps, it can be found that the spectral energy distribution curves of the two compact fluorescent lamps are basically similar, except that the compact fluorescent lamp with a color temperature of 6 400K is in the spectrum of a compact fluorescent lamp with a color temperature of 2 700K. The shortwave component is more. The tester’s difference in response time to various color target spots under two color temperature compact fluorescent lamps is obvious, and the driver is more likely to find obstacles rich in short wave components in the high color temperature illumination environment, but for yellow and green obstacles. In terms of matter, the difference in response time of the driver in different color temperature lighting environments is not as obvious as that of blue obstacles.
Although the experimental results show that the high color temperature light source is better for tunnel lighting, the tunnel lighting can not only consider the driver’s reaction time, but also consider the influence of the tunnel air condition on the lighting effect. The response time of the driver obtained in the laboratory in different light environments can only be used as one of the factors for the choice of tunnel illumination source. The choice of tunnel illumination source should also consider the various influencing factors of the tunnel illumination environment.
1) Under the same conditions, the higher the color rendering index of the tunnel illumination source, the more favorable the driver is to identify the obstacle. There is a positive correlation between the two, which is beneficial to driving safety and lighting energy saving. In the tunnel lighting design, to meet the safety and comfort of lighting, and to consider energy saving, the source of high color rendering index should be selected as much as possible.
2) In the tunnel lighting environment where the color is considered, the greater the background brightness, the shorter the driver’s reaction time, and the corresponding visual effect is better. When the background brightness is fixed, for a tunnel illumination source with similar spectral energy distribution curve, the driver has better visual effect and better illumination effect in a lighting environment rich in short-band components. When the target color is rich in short-wave components, it is easier to find in high color temperature lighting environment.
Post time: Jan-04-2019