Lighting design: what are the factors that affect the quality of road lighting? (three)

The following two types of instructions:

A, due to the increase of the effective background brightness, just can see the brightness contrast of the object that is the threshold contrast Cth decreased, the ability to improve. Formula: Lbeff - effective background brightness

B, effective contrast reduction. Formula: Ceff - effective luminance contrast

On the one hand, due to the increase of background brightness, the contrast of the threshold is reduced, on the other hand, the contrast is reduced, but the positive effect of the reduction of the threshold contrast is not enough to compensate for the loss of effective contrast. In other words, in the absence of glare, an object can be seen (threshold contrast). Under the glare of the role, it is not clear, we must increase contrast to see. This part of the increase in contrast with the original contrast, it is the expression of visual function due to the loss of energy loss caused by a measure of the decrease, known as the threshold contrast increment, referred to as threshold increment.

When the road surface brightness range of 0.05cd/m2 < Lav < 5cd/m2, the threshold increment TI formula is as follows:

In type:

Lav - the observer's adaptation luminance (cd/m2)

Eeye - the illumination (LX) produced by the surface of a luminaire in the observer's view perpendicular to the line of sight in the eye

The contribution of all lamps in the observer's field of view to TI

The angle between the line of sight and the center line of the human eye to the light of the lamp (line of sight below the horizontal line of 1O and passing along the longitudinal vertical plane of the observer's eye).

The TI is the third parameter to evaluate the quality of lighting.

Three, visual comfort

The requirements of visual comfort and visual function, the purpose is to ensure the driver's visual reliability, thereby ensuring the safety of driving. Visual comfort is a kind of psychological function, which is mainly determined by subjective evaluation, but it can guarantee the quality of lighting by restricting some parameters. And visual function, visual comfort is also affected by the lighting level, uniformity, glare three lighting parameters, as follows:

1, lighting level:

Under the condition of keeping the glare level is low, the average brightness of the high road will make the driver feel more comfortable. Therefore, the average luminance of the road is not only an important parameter for visual function, but also an influential parameter for visual comfort.

2, uniformity:

When the vehicle is traveling on the road, there will be a light and dark area in front of the road, there will be a rhythm of flashing. It is called the "speckle effect" phenomenon. This phenomenon will interfere with the driver, causing visual and mental fatigue. This is also a cause of the impact of visual reliability accident. Therefore, fourth kinds of lighting parameters, the longitudinal uniformity (UL), which affect the reliability of vision, are proposed:

In type:

UL longitudinal uniformity

L, min - lane center line minimum brightness

The maximum luminance of Lmax Lane centerline

3, glare:

Glare has a great influence on the driver's visual comfort. According to the experimental results, the degree of discomfort glare can be measured by glare control level (G). This is the fifth parameters that affect the reliability of vision, which is mainly affected by the characteristics of the lamp and the characteristics of the device in two areas.

The expression is as follows:

In type:

G glare control level

I80, I88 - illumination in the vertical plane parallel to the road axis and the vertical axis of the lamp in the angle of 80 degrees and 88 degrees of absolute light intensity;

F - the illumination area of the illuminator in the 76 degree direction perpendicular to the axis of the road and the vertical axis of the lamp;

C - light source color correction factor; (low pressure sodium lamp =+0.4; high pressure sodium lamp =+0.1; high pressure mercury lamp =-0.1; other bulb =0)

Lav - Road average brightness;

H - the vertical distance between the horizontal line of sight and the height of the luminaire (lamp height - 1.5m);

P - the number of lights per kilometer.

The formula is an empirical formula, in which the square brackets represent the characteristics of the lamp, which is called the lamp index (SLI).

4, induced:

The lighting along the road to the appropriate configuration, so that vehicles, pedestrians on the road ahead of the road, the route and the relevant configuration, such as a clear visual conditions, which is called the road lighting induced. Although we can not give a quantitative parameter in this respect, it is also an important factor that can not be ignored for visual reliability.

In road lighting, in order to enhance the optical induction, the following methods are generally adopted:

A, straight line road lighting configuration, should be parallel with the road, neat;

B, at the corner of the road lighting device shall be installed in the outer corners;

C, intersection with different light source of road lighting;

D, different streets use different types of light sources;

In addition to the above mentioned factors, different light sources have different effects on the visual reliability due to their different emission spectra. In recent years, with the development of the LED light source and its application in road lighting field is increasingly popular, but the research on the effects of LED light source for road lighting environment in motor vehicle driver's visual reliability is not comprehensive and thorough, still need to further expand the road lighting workers, in order to promote the application of LED light source of science, promote the development of green lighting.