1. Background introduction of LED road lighting system
In order to meet the urban road lighting design standards, traditional road lighting fixtures often use bulbs that consume more than 200 watts of mercury. In contrast, by 2009, the optical efficiency of light-emitting diodes (LEDs) on the market has exceeded 100 lm/W, which means that the power consumption of street lamps using LEDs as light sources will be greatly reduced. Due to the long life of the LED, mercury-free and energy-saving features, it is a good choice to replace the traditional LPS (low pressure sodium lamp) or MH (metal halide lamp) with LED as the light source. At present, LED street lights have been tested in various countries around the world. In order to solve the problem of energy shortage and greenhouse gas emissions, LED street lamps have been put into practical use in some places, and the governments of some regions and cities in China, North America and Europe have actively promoted them.
Since most of the LEDs on the market are distributed in the Lambertian distribution, the central light intensity is relatively strong, and it is a symmetric circular spot distribution, which cannot be directly used for road lighting. In order to meet the urban road lighting design standards, LED street lamps need to be designed with secondary optics to produce a rectangular, evenly distributed spot whose light distribution curve needs to be in the shape of a batwing. In addition, the quality of the optical design directly determines the efficiency of the LED street light. Some LED street lights are added with a poorly designed secondary lens. Some of the light is lost after multiple reflections in the lens or cannot be matched. In the area, some secondary lenses have a spot shape and uniformity, but the light extraction efficiency is reduced by nearly half. In addition, the quality of the optical design is also determined whether the LED street lamp has glare, and some poorly designed lenses, although it can also produce a rectangular, evenly distributed spot, the light distribution curve can also be a batwing, but because Without the cut-off design, there are still a lot of outgoing light in the range of 75ï‚°~90ï‚° along the road, which will cause glare to distant vehicles or pedestrians.
Good optical design should make full use of the advantage of small area of ​​LED light source, fully consider the utilization of light, distribute all the light emitted from the LED chip to the road surface, form a uniformity, no glare, and the light distribution curve is bat. The spot of the wing. This article will explore the optical system design and development trends of LED road lighting systems based on these factors.
2. Design method of free-form surface secondary optics
Since road lighting requires that the spot of the street lamp be rectangular, in the direction perpendicular to the road, the outgoing beam is concentrated, and in the direction of the road, the outgoing beam is divergent and has a large viewing angle. For such a direction is convergence and the other direction is divergent light distribution, then the corresponding lens should have a positive lens in the cross section perpendicular to the road direction, and the cross section along the road should be a negative lens, so The entirety of the lens can be expressed by an irregular free-form surface.
In order to meet the urban road lighting design standards, traditional road lighting fixtures often use bulbs that consume more than 200 watts of mercury. In contrast, by 2009, the optical efficiency of light-emitting diodes (LEDs) on the market has exceeded 100 lm/W, which means that the power consumption of street lamps using LEDs as light sources will be greatly reduced. Due to the long life of the LED, mercury-free and energy-saving features, it is a good choice to replace the traditional LPS (low pressure sodium lamp) or MH (metal halide lamp) with LED as the light source. At present, LED street lights have been tested in various countries around the world. In order to solve the problem of energy shortage and greenhouse gas emissions, LED street lamps have been put into practical use in some places, and the governments of some regions and cities in China, North America and Europe have actively promoted them.
Since most of the LEDs on the market are distributed in the Lambertian distribution, the central light intensity is relatively strong, and it is a symmetric circular spot distribution, which cannot be directly used for road lighting. In order to meet the urban road lighting design standards, LED street lamps need to be designed with secondary optics to produce a rectangular, evenly distributed spot whose light distribution curve needs to be in the shape of a batwing. In addition, the quality of the optical design directly determines the efficiency of the LED street light. Some LED street lights are added with a poorly designed secondary lens. Some of the light is lost after multiple reflections in the lens or cannot be matched. In the area, some secondary lenses have a spot shape and uniformity, but the light extraction efficiency is reduced by nearly half. In addition, the quality of the optical design is also determined whether the LED street lamp has glare, and some poorly designed lenses, although it can also produce a rectangular, evenly distributed spot, the light distribution curve can also be a batwing, but because Without the cut-off design, there are still a lot of outgoing light in the range of 75ï‚°~90ï‚° along the road, which will cause glare to distant vehicles or pedestrians.
Good optical design should make full use of the advantage of small area of ​​LED light source, fully consider the utilization of light, distribute all the light emitted from the LED chip to the road surface, form a uniformity, no glare, and the light distribution curve is bat. The spot of the wing. This article will explore the optical system design and development trends of LED road lighting systems based on these factors.
2. Design method of free-form surface secondary optics
Since road lighting requires that the spot of the street lamp be rectangular, in the direction perpendicular to the road, the outgoing beam is concentrated, and in the direction of the road, the outgoing beam is divergent and has a large viewing angle. For such a direction is convergence and the other direction is divergent light distribution, then the corresponding lens should have a positive lens in the cross section perpendicular to the road direction, and the cross section along the road should be a negative lens, so The entirety of the lens can be expressed by an irregular free-form surface.
