| Because of their light weight,low power consumption and low radiation,the liquid crystal displays(LCD)TVs have occupied a pivotal position in so many kinds of flat plane display TV products.Liquid crystals cannot emit light by themselves,and must be illuminated by a backlight unit.Therefore,some important display indicators such as color gamut,brightness,and contrast are determined by the type of backlight.With the development of social economy,people put forward higher requirements for display color gamut and brightness,which cannot be met by LEDs and other traditional light sources.However,Laser has the natural advantages of high brightness and high monochromaticity.It is an ideal choice for LCD TV backlight.For this reason,a backlight unit using scanning beam splitting system with speckle suppression is proposed in this paper.Firstly,we introduced the development history of LED LCD TVs and their advantages and disadvantages compared with organic light-emitting diode TVs and quantum dot TVs.With the cost of oled TV and qd-led TV reduced in the future,LED LCD TVs will face the crisis of shrinking market.Using laser as their backlight unit,lcd-tvs can improve the display performance and retain the cost advantage at the same time,which is helpful to develop the market better.Then,we investigated some laser backlight schemes at home and abroad and found that multiple lasers were used as their illumination source in these schemes.Generally speaking,the higher the optical power of the laser,the higher the ratio of power to price,so the use of high power laser can reduce the cost.However,multi-beam illumination is a necessary means to generate uniform backlight.In this paper,the scanning beam splitting system divides the high-power laser beam into uniform sub-beams emitted by the multi-mode fiber array for the laser backlight source,and has certain speckle suppression ability.Multimode fiber arrays have one-and two-dimensional forms and with their own advantages in the backlight systems.So we designed a 1-D scanning beam splitting system and a 2-D one for the different arrays,respectively.Using the Zemax simulation software,the optimization design of the two kinds of systems is carried out,and the scanning simulation is carried out using Zemax macro language.The uniformity of the theoretical sub-beam is calculated by simulation.According to the simulation parameters,two kinds of scanning beam splitting systems are studied experimentally.The simulation and experimental results show that the simulation results of the 1-D beam splitting system were as follows: the power coefficient of variation(PCV)among 19 sub-beams was 0.43,and the PCV among the remaining sub-beams after the removal of 4 significant bright beams was 0.18.The corresponding experimental results generated 18 sub-beams with an PCV of 0.26,and the PCV of the remaining beams after the removal of 4 significant bright beams reacheed 0.1.The 2-D system simulation results show that the PCV of six sub-beams was 0.15,and the experimental results show that the PCV of six sub-beams was 0.07.The power distribution trend of the simulated and experimental beams was the same but with some numerical differences.The experiment also verified that both systems have the function of speckle suppression.The more important significance of the experiment is to verify that the scanning beam splitting system applied to the backlight of laser TV can effectively provide uniform backlight with speckle free. |
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