LED direct backlight lens design based on modulation of paraboloid inner surface for uniform illumination

In the system of near-field uniform lighting, lens design methods commonly use sphere as the inner surface, and the calculation of the free-form surface only considers primary reflection . But when the angle reaches a certain scope, total reflection on the free-form surface of the lens is easy to occur ,which will lead to the poor illumination performance. In order to get the larger light distribution in the near-field lighting system ,a free-form lens design method based on the modulation of the parabolic inner surface was proposed. The parabolic can diffuse the energy of the light source, and then calculate the free-form surface. Through simulation, the uniform light spot with 40 mm radius can be realized at 15 mm distance away from light source, while the uniformity reaches 95%, the efficiency reaches 97.8%. Comparing with traditional direct lens, the uniformity is enhanced and the height of backlight box is decreased by using the structure of this lens.