# High-Resolution Pixel LED Headlamps: Functional Requirement Analysis and Research Progress
## 3 Research Progress of High-Resolution Headlamps
### Structure and Performance of Existing High-Resolution Headlamps  
[PERSON] showed a 3 \(\times\) 11 LED array light distribution module [37]. As shown in Figure 4, the LED adopts Philips' small ceramic LED, the size is 2.3 \(\times\) 1.9 mm, the driving voltage is 1.5 A, and the highest it can achieve is 265 lumen. The LEDs are collimated by a near-mode collimator and then distributed through a projection lens, which can achieve an angular resolution of 1.5\({}^{\circ}\), and each LED can be individually controlled. The distance between the light source and the optical system determines the resolution of the system and also determines the brightness of the center point. Due to the Lambertian luminescence characteristics of LEDs, a short focus system is generally used. The problem of dazzling oncoming vehicles can be avoided, and a 15\({}^{\circ}\) cut-off line of light and dark is generated through high contrast, which realizes far and near light illumination and anti-dazzle functions of the car lights. Audi's matrix headlamps [38] consist of 25 LEDs; each LED chip generates a main beam segment in the form of a vertical strip. A total of 25 LEDs form 25 light segments, each of which is independent and affects the others. Cars along the road can produce 100-150 lx luminous flux, thus the driver can clearly see the road with high beams. The matrix beam design allows each light segment to work independently as a camera or a sensor. When an oncoming car is detected, the anti-glare effect can be achieved by turning off the LED of the light segment. The advantage of this technology is that the area dimming is not realized by mechanical blocking or rotation, which facilitates more energy-saving and reduces the volume. However, due to the limitation of LED volume, there is still the problem of insufficient flexibility. Osmam developed of the first-generation LED matrix system \"Smartrix\" [39]. The light source is the Oslon Black Flat from Osram Opto Semiconductors with its low thermal resistance and high output even under extreme conditions, as shown in Figure 5. The biggest advantage of this module is the long-life silicone optics used as the collimation system of the LED system. The entire optical system is relatively small and compact, with good heat resistance and freedom, and its degree is high. The LED adjusts the input current on the voltage regulator through PWM, and each LED can be independently controlled. Compared with matrix light, it not only has an anti-glare function but also can be used for static low beam. There are 3 \(\times\) 12 LED lights, which can adapt to the needs of different types of vehicles. Figure 4: LED matrix using pre-optics projection lens. Figure 5: The dimensions of the Smartrix module. The luxeon chip developed by Lumides solves the problem of chip size. The matrix HD84 headlight module launched by HELLA used this chip to produce HELLA's first high-definition digital headlight [40]. The size of the chip is only 0.5 mm\({}^{2}\); it has a high voltage low current and good heat dissipation performance, and its single luminous flux can reach 150 lm under 750 ma current. In addition, the light-emitting area accounts for more than 95% of the overall size of the chip. This model uses 84 independent silicon lenses to collimate the LEDs, and then the rays after collimating through a preset lens are projected by area division to achieve the illumination of 84 areas at 25 m. Compared with the traditional LED headlights, the flux is increased by 2.5 times to 84 light segments. The 84 light segments are independent of each other, and the brightness of each LED can be controlled by the corresponding control system. When the camera or the sensor detects an oncoming vehicle, the system can selectively turn off or reduce the brightness of the corresponding LED to reduce driver dazzling.