Designing single LED illumination distribution for direct-type backlight.

This study presents a new method for achieving uniform illumination of an LED array by designing single LED illumination distribution (SLID) on the target plane. The SLID with the least coefficient of variation of the root mean squared error is calculated. For square LED arrays, the uniformity of illumination reaches 0.94. A secondary lens was designed to achieve the calculated SLID. Simulation results show that the uniformity of illumination reaches 0.92 when the distance-height ratio is 3.33. The calculated SLID can be used in different distance-height ratios. When the distance-height ratio is 5, the uniformity of illumination reaches 0.91. The calculation method can be used in different kinds of LED arrays. A feedback method of lens design is presented for a real direct-type backlight system.