Currently, more and more complex headlamp systems are finding their way into cars, with LED bulbs increasingly replacing the traditional halogen and xenon headlamps. In the short term, LEDs will completely displace xenon headlamps and, in the long run, replace halogen headlamps as car manufacturers switch from static bulbs to dynamic and aesthetically pleasing LED lighting.
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Dazzling and poor visibility at night
As the US National Highway Traffic Safety Administration (NHTSA) reports, in the United States in 2015, approximately 30 percent of traffic accidents occurred at night. IHS Markit also announced that 50 percent of all crashes in the United States are due to poor eyesight. As a result of the aging population, this proportion is likely to increase.
According to the Technical University of Darmstadt, older drivers tend to experience different types of impaired vision. In addition to reduced visual acuity, an age-related pupil reduction and a slower adaptation to the dark should be mentioned here. People between the ages of 60 and 65 need about twice the brightness and contrast and can only handle half the glare to achieve about the same vision as 25-year-olds.
Even though high-beam glare can distract attention or even cause temporary blindness, in the past it has always been up to motorists to avoid such glare. For this, they only had a switch available to switch between dipped and main beam. The consequence is that during night driving, motorists have their finger on the dimmer switch most of the time to switch between high beam (when on the road alone) and dipped beam (when other vehicles are in the field of view). Would it not make sense for motorists to keep the high beam switched on for better visibility?
Model the light cone and project information
As a combination of driver assistance systems (ADAS) and exterior lighting, adaptive high beams can partially darken the shaft so as not to dazzle oncoming traffic at these points.
Texas Instruments (TI) has further developed this concept and is opening up new possibilities in vehicle lighting technology with Digital Light Processing (DLP). A DLP chipset can control the front light of a car in great detail. Automobile manufacturers and Tier 1 suppliers are thus able to control up to one million pixels per headlamp individually. With this technology, headlights can not only fade out particular areas where other drivers or pedestrians would be dazzled but also project information onto the road, such as lane boundaries or guidance.
CMOS memory cells move micromirrors
The central element of a DLP chipset is an array of aluminum micromirrors called the Digital Micromirror Device (DMD). Depending on the configuration, DMDs contain hundreds, thousands, or even millions of individually controllable micromirrors, with one CMOS cell under each micromirror. Each mirror includes a flexible mechanical support structure that allows the mirror to be suspended using two address electrodes. These electrodes are connected to the memory cell and generate equal electrostatic forces to bring the mirror into one of two possible static positions.
Integrated into an optical system, the DMD acts as a symmetrical bistable optomechanical element in which the position of each mirror determines which direction the incident light is reflected. The high frequency of operation and small pixel size of a DMD allows for fast modulation and compact system latencies, enabling car manufacturers to more precisely control the light thrown on the road and give the driver better visibility.
DLP Pixel Light
DLP-based systems are suitable for all kinds of light sources, including LEDs, laser-phosphor solutions and direct laser bulbs, which can be designed to reduce power consumption and use smaller, more attractive styled lenses than existing adaptive high beam solutions. The DLP technology is not only efficient and scalable but also allows precise control of the headlight beams to improve visibility and visibility in low light conditions.
Various glare-free headlight solutions either dim single LEDs or move the beam down or to the side. Some answers automatically switch between low beam and high beam, and others turn when the vehicle shifts into a bend. In principle, all these systems are based on switching off or blocking the light from their headlights so as not to dazzle oncoming or preceding vehicles. LED matrix headlights usually reduce glare by switching off some LEDs.
Short latencies instead of complex algorithms
Undoubtedly, the automatic turn on and turn off function using given beam patterns is a step in the right direction. However, they do not yet provide the level of control required to develop real-time adaptive headlamps. Such a high-level resolution and adaptability is attractive because it can enable ADAS functions such as the illumination and detection of traffic signs. These, in turn, are needed as the industry moves towards semi-autonomous and fully autonomous driving.
TI’s DLP technology for high-resolution headlamp systems (DLP pixel light) reduces glare for different objects, such as pedestrians or drivers of oncoming vehicles. Minimizing the system latency between providing sensor data and the headlight system response eliminates the need for complicated or even artificial intelligence based algorithms to predict where an object will move next. The fast and direct control achieves a high degree of accuracy, as more pixels can be used on one degree of viewing angle. This gives the system a greater light throughput, allowing more light to get onto the road with precise control. Chip-on-Board (COB) Led Grow Light another similar kind of technology.
The high-resolution system with small dimensions
A system based on DLP technology uses additional sensor data and darkens those light pixels that aim at the windscreens of oncoming cars and thus cause glare to their drivers. The highly detailed control of the single-pixel headlight allows adaptive high-beam functions for better visibility and comfort during night driving. The block diagram of a DLP headlamp system with integrated DLP chipset.
The DLP5531-Q1 chipset for high-resolution headlamp systems provides designers with more customizable beam patterns for more precise control over the distribution of light on the road – with smaller system dimensions. A partial or complete darkening of individual pixels allows a permanently activated high beam while driving, without dazzling other road users.
Future applications of headlamp technology
While many automakers and Tier 1 suppliers focus on the benefits of improving visibility, the DLP technology is further characterized by programmability. It can, therefore, be flexibly configured for new functionalities, as required by semi- and fully autonomous vehicles.
In conjunction with driver assistance systems, DLP headlamp systems can illuminate specific points, such as traffic signs, with just the right amount of Led light, thus ensuring clear visibility.
DLP lighting systems are also able to project images such as lane markings or navigation instructions onto the road ahead of the vehicle. But improving communication between drivers, pedestrians and other cars is becoming increasingly important as the industry continues to evolve. Correctly programmed, a DLP pixel light headlamp system can signal to a pedestrian by signal or sign what the vehicle is about to do next.