The average illuminance of road surface is one of the evaluation indexes of traffic road and pedestrian road lighting, and also an important reference index for how to design and configure street lamps. LED street lamp manufacturer is a solid cold light source, which has the characteristics of environmental protection, pollution-free, low power consumption, high luminous efficiency, long life, etc. Therefore, LED street lamp will become the choice of road lighting energy-saving transformation. LED street lamp is an efficient solid state light source based on semiconductor PN junction, which can emit light with weak electrical energy. Under a certain forward bias voltage and injection current, holes injected into the P area and electrons injected into the N area diffuse to the active area and emit photons after radiation recombination, directly converting electrical energy into light energy. In order to use solar LED street lamps to configure or replace urban or rural roads, the calculation of lighting related indicators should be considered first. LED street lamp is an efficient solid state light source based on semiconductor PN junction, which can emit light with weak electrical energy. Under a certain forward bias voltage and injection current, holes injected into the P area and electrons injected into the N area diffuse to the active area and emit photons after radiation recombination, directly converting electrical energy into light energy. The method of "utilization coefficient" is a simple and effective method

The formula calculated by "utilization coefficient" method absolutely reflects the conclusion of traditional lighting theory research. What we need to do is to input some experimental or theoretical data of LED street lamps into the formula, get the results and compare them with the requirements of road lighting design standards. It goes without saying that these calculations are also necessary for the design, development, improvement, improvement and marketing of LED street lamps.

1 Concept

The utilization coefficient (u) is the ratio of the luminous flux directly illuminating on the road surface to the luminous flux emitted by all light sources, which is related to the height, height, layout and width of the street lamps.

The luminous flux (π) is the sum of the energy emitted by the light source and the energy received by the human eye. It indicates how much light energy is radiated in unit time, in lm. Other representations: cd.sr (cd is the unit of luminous intensity: candela. sr is the unit of three-dimensional angular surface degree.

Illuminance (E) is the proportional coefficient between the luminous flux and the illuminated area in LuxLX. 1Lx refers to the average luminous flux of 1lm distributed in the area of 1m2 energy (i.e. lm/m2).

The average illuminance of road surface (EAV) is the average illuminance of each point measured or calculated at a preset point on the road surface according to relevant regulations.

Maintenance coefficient (k) refers to the ratio of the average illuminance or average brightness on the specified surface to the average illuminance or average brightness obtained on the same surface when the equipment is newly installed under the same conditions after a period of use.

The installation height of the lamp (h) is the vertical distance from the light center of the lamp to the road surface.

The installation distance between lamps is the distance between two adjacent lamps measured along the road centerline.

Cantilever length (XL) is the horizontal distance from the center of the lamp of the lamp to the adjacent side edge, i.e. the horizontal distance of the lamp extending or retracting the rim.

The effective width of pavement (WEFF) is the theoretical width of pavement used for road lighting design. It is related to the actual width of the road, the cantilever length of lamps and the layout of lamps.

2 Calculation formula

According to the definition of illuminance, e=< s>/ a

(1) In the formula, A-irradiation area, M2

Average road illumination, Eav=F/(W * S)

(2) Where, f-rated luminous flux of street lamp light source, lm;

Road width, m.