Studies on primary lens for LED light source to enhance lateral emission intensity

Typical LED light sources have lower light utilization efficiency (LUE) in reflective directional illumination applications due to light pattern mismatch. Light patterns are generally controlled by secondary optical systems, which are heavy and large. Compared with the secondary optical system, the primary lens is smaller in size, lighter in weight, and more efficient in light extraction. This work is a preliminary study on the primary lens of LED in order to improve the LUE of LED in reflective directional illumination fields. Experimental result shows that the light extraction efficiency (LEE) of LED light source packaged by a primary optical lens is improved by a maximum proportion of 16.3%. The LUE of the LED packaged with the primary lens is up to 40.1% at 60°. After encapsulating the primary lens, the weighted mean angle of light intensity in the full space is at 57° which is bigger than that of LED without primary lens (46°).