Bi-function Poly-Ellipsoidal System (PES) solution for a headlamp has been widely used in automotive lighting today. Generally speaking, an opaque shutter is utilized to enable switching between a high beam (also known as an upper beam) and a low beam (also known as a lower beam). There are several main approaches to realize such a shutter function. Two most common examples are discussed as follows.
In a first category of examples, a moveable shutter is adopted. As shown in FIG. 1, the front-lighting system 1 in this case may comprise a LED 11, a reflector 12, a projection lens 13 and a moveable shutter 14. Here, LED 11 serves as a common light source for both high beam and low beam. Specifically, the moveable shutter 14 is configured to switch between the low beam and the full high beam. Traditionally, in this kind of moveable shutter solution, a solenoid valve is needed to control the moveable shutter 14, which is not cost-effective.
In a second category of examples, a fixed shutter 24 is used, see details in FIG. 2. In addition to a projection lens 13 as in FIG. 1, two different light sources for the high and low beams (i.e., the low-beam light source LBS and the high-beam light source HBS) as well as their corresponding reflectors (i.e., 21 and 22) are also provided respectively in the front-lighting system 2. To be specific, the high-beam and the low-beam light sources LBS, HBS can be installed back-to-back in one holder 23. In view of this, the two light sources LBS, HBS will be very close, and the space between them is not enough to dissipate the heat away, which they produce aside of the light. Therefore, active cooling measures are usually required in such a situation. Besides, due to a thickness of the shutter 24 itself, a dark area DA exists in the final projected beam pattern which is clearly visible in FIG. 3. Additionally, a non-uniform color caused by dispersion is often easy to see in this case.
CN105570794A disclosed a condenser in front of the high-beam light source which condenser is further arranged to shade a small part of the light rays of the low-beam light source, i.e., to avoid, by refraction and total internal reflection within the condenser, this small part entering the projection lens.