Design of large angle directtype LED backlight lens

Costcutting schemes have been proposed more and more in liquid crystal display (LCD) display field. Aiming at the backlight system of LCDTV, a large angle backlight lens design was proposed. Using a specific doublefree surface design, the first hole is set to be elliptic structural surface, which could classify the emergence luminous flux from light source as equal angle. Based on the corresponding relationship between the ideal illumination distribution of receiving screen surface and the exiting luminous flux of every angle of the first hole, the freeform curve of light emitting surface was calculated. Then by means of microstructure processing at the bottom and according to the requests of mould and molding product,the appearance structure was completed, and finally the scheme meeting the design index was achieved,which could effectively solve the macular problem caused by increased angle and satisfy the evenness requirement for target receiving surface. For a 32 inch LCDTV backlight module, 12 LED lamp beads with the max forward current of 350 mA were utilized, in the system with the module height of 30 mm, the designed backlight lens module could match the demands of brightness and uniformity.