How to Realize the Design of Light Distribution-Part One

LED luminaires have taken the lighting industry a big step forward and achieved significant energy savings. The basic function of lighting fitting is to provide an electrical connection to the light source. However, today users are concerned about more than just whether the basic function of the lamp can be achieved. It's more about whether the light can illuminate where we want it to light and whether the lamps bring us the vision comfort while realizing illumination function.

Light sources that emit light in all directions are wasteful for most applications unless required. they are likely to cause glare to a great extent. Therefore, for most lamps, adjusting the light to the desired orientation while minimizing the light loss and reducing the glare from the light source is the main object of light distribution design.

Light distribution is one of the most important optical properties of a luminaires.How to control the light distribution? we first analyze the first method - controlling the light distribution through the lens. 

The first lens is directly encapsulated (or glued) on the LED chip board.In theory, LED chips can emit 360 degrees of light. But in fact the chip's maximum Angle of illumination is 180 degree or slightly bigger than 180 degree  (affected by spill light).This is because The chip is encapsulated and placed on the LED board and o that the back side cannot transmit light. Generally speaking, the angles obtained by primary lens are mostly symmetrical .some common angles are 180°, 160°, 140°, 120°, 90°and 60°etc .  Once light angle of LED chip is fixed at the time of encapsulating, it will be unchangeable. So the design of light distribution in this paper refers to the use of secondary lens.

A lens is an optical element whose surface is a part of a sphere and is made of transparent material. The principle is to use the law of refraction of light. Covering the lens on light source can change the direction of the light or control the light distribution.  The result of changing the direction of the light and the refraction angle are determined by  three factors of lens-incident plane,material refractive rate and exit surface . As shown below (cross section), this is a cross section of a single lamp bead with a secondary lens.

In addition to the single lens, lens manufacturers have also developed lens module to meet the needs of different luminaire manufacturers. Below are some single lens and lens module of led street lights.

Generally ,the light spot of the lamp is circular.the lens is mostly axisymmetric body (cross section 2) . and its design is relatively simple . while the shape of lens whose spot is non-circular is generally non-axisymmetric (cross section 3). Here are some examples of them.

However ,In the actual demand of light distribution , things are far more complex. with no light distribution design , the light spot of street light is a  shape like round and about 50% light spills over into areas  that does not need lighting, which lead to low light utilization , unnecessary energy waste and  lighting pollution nearby. The best lighting distribution target should look like the one shown on the right. a light distribution like this can be achieved through using lens ,but unconventional.

For example,  the bat-wing light distribution, which is commonly used for street lighting, also known as the type I optical distribution,the lens is neither an ordinary axisymmetric nor a non- axisymmetric body. It is a double-end lens used to form the light spot similar to the rectangular (shown as the below pseudo-color diagram). General type I light distribution is usually used for one-way street, side road ,  path and footpath lighting.

Different lenses can be used to achieve different light distribution design requirements, but it is meaningless to talk about light distribution design without specific luminaires. Lighting design and light distribution design seem to be separate, but in fact they are a unified whole. AGC Lighting have not only made remarkable achievements in the field of street lighting manufacturing, but also fully considered the diversified demands of road lighting for clients. we combine luminaire design with light distribution design of   extensive requirements, allowing clients to easily address any road lighting project.