Unlike traditional lighting, LED has the characteristics of point light source, high brightness and narrow beam output. When designing LED street lights, the first consideration is to make full use of the limited luminous flux to the effective illumination range. The street light requires the lighting effect of the road, and the open space beyond the road is not the place where the street lights need to be illuminated. The light becomes a long strip of light that spreads along the road surface, and at the same time, the control of glare must be taken into account, so higher requirements are placed on the designers of LED lamps. In terms of optical design, the radiation forms of LEDs include Lambertian, side-firing, bat-wing and concentrating. In the field of road lighting, according to the design experience, the Lambertian type and the manta potato type are more suitable. Through the secondary optical design, the illumination range and luminosity curve of the LED can meet the needs of road lighting.
There are no more than two ways in the products launched by many manufacturers. With or without a lens, it should be emphasized that, from the perspective of the actual luminous flux and color temperature consistency of today’s LEDs, it is particularly important to optimize the design of the light distribution to improve the uniformity of the illuminated road surface. In the light distribution design of LED lamps, a simple, efficient, mass-produced, and easy-to-install LED condensing reflector should be used to improve the light output efficiency and effectively control the light output angle and light intensity distribution.
The high-efficiency concentrating reflector adopts a grid-like method. Each LED corresponds to a reflection groove. The holes in the groove correspond to the installation positions of the LEDs. The LED reflected light corresponding to each hole is irradiated vertically by the LED lamps. The light spot formed on the surface is an elliptical light spot, which mainly uses the reflection of light to distribute the light in an elliptical range. The surface of the reflective groove is coated with a reflective film, and the reflective film is preferably a chrome film or a nickel-chromium film. The light emitted by the LED is uniformly gathered and reflected to the required area. The light efficiency is high and there is no obvious spot, which improves the lighting distance and effect of the lamp. The LED has the characteristics of directional lighting. Light sources such as high-pressure sodium lamps and metal halide lamps emit light to the whole space.
Compared with the envelope angle of the reflector to the light exit surface, a large part of the light emitted by the traditional light source can only be emitted after being reflected or refracted by the optical system. The utilization efficiency of the light by the optical system determines the overall efficiency of the lamp, and the traditional light source Its own volume is large, and the efficiency of the lamp is reduced due to the absorption and reflection of secondary light.
LED has the characteristics of emitting light into half space, which greatly reduces the proportion of light absorption by the light source. This is the second advantage of LED lamps in terms of lamp efficiency. LED has the characteristics of small size and similar to point light sources. In addition to absorption and retention, it also provides great convenience for the secondary optical design of the matching lamps, ensuring the high efficiency of the optical structure and the accuracy of the optical path control. A large part of the non-imaging light used in lamp design is the practical application of classical geometric optics, that is, a large number of quadratic or even multiple curves are used as lamp reflectors or lenses. The closer the light source itself is to the point light source, the more satisfying The approximate conditions of classical geometric optics make the design closer to the actual result and the optical device can control the light more accurately.