| 摘要 |
<p>Disclosed is a primary lens for LED used in a direct type backlight module. The dispersion index of the primary lens for LED is smaller than 0.1, and the dispersion index is defined in formula (I), wherein dA is a differential element of area on the primary light emitting surface of a LED wafer, di is a solid angle when the dA light is incident on the lens and the incident angle just falls in the critical region ,wherein the critical region is referred to the region in which the dispersion is occurred in the lens for the light with various wavelengths emitted from the LED. Corresponding to the differential element of area dA, the total solid angle for color separation is followed by formula (II), wherein dtotal is the solid angle of the light emitting surface of the lens corresponding to any differential element of area dA. With the lens, a wide emitting brilliance is ensured and the dispersion is avoided. A backlight module and a liquid crystal display device including the lens are disclosed.</p> |
