The Design And Fabrication Of The Straight Down Type LED Backlight Lens

With the continuous progress of technology,the luminous efficiency of LED enhances unceasingly.As a new type of green and energy-saving light source,LED has been attracted extensive concern from governments and institutions.The backlight module using LED as the light source is widely used in LCD TV,panel lights,advertising light boxes,and other fields.Compared with the side type backlight module,the straight down type backlight module has the benefits of higher brightness,higher energy utilization rate,better uniformity and more simple structure.But it needs a backlit cavity to mix the light,a disadvantage of it is that its thickness is too thick.The backlight lens can modify the outing light distribution of LED,so it can reduce the thickness of the straight down type LED backlight module and decide the optical performance of the whole back light module.The straight down type backlight LED lens is generally divided into transmission type and reflection type.Compared with the transmission backlight lens,the reflective backlight lens has higher optical efficiency,shorter mixing light distance and wider application range.It has an important research significance and application value.But the reflection backlight lens contains multiple optical surfaces that all affect the optical effect,and all these optical surfaces should be reasonably collocated to achieve the uniformity requirement,so it is more complex and difficult to design the lens.For the straight down type backlight LED lens' design,producing and testing,this paper makes research mainly in the following aspects:1.This paper refers to grid partitioning method and then solves the initial structure of the backlight lens which is based on the point source model.In order to make the point source can represent the optical characteristics of LED;this paper optimizes the light intensity distribution of the point light source.2.For the design of backlight lens that uses LED as the light source,this paper optimizes the surface shape and determines the key parameters of the lens on the basis of the initial structure which is solved from the point light source.For the free-form surface design,this paper uses the method of optimizing the each segments of the polyline;For the optimization of the polyline,one point can affect the connected two lines when it is changed,so the author proposes to use the slope of line as the variation;In the optimization,the author makes an ASAP code generation tool in combination with Excel VBA scripts.3.In the production of the backlight lens,to reduce the errors between the mould and the design,this paper makes a macro tool to translate the free-form surface into the machine point set.To enhance the backlight lens' central region illumination,this paper makes the sidewall of the backlight lens to be rough surfaces and adds microstructures at the bottom of the backlight lens.The roughness and the microstructures would be decided according to the actual lens optical effect.To analysis the overall uniformity and find the local flaws of the LED backlight module,the author makes a brightness uniformity analysis tool,and carries out the related testing work of the backlight module.