“Traditional automotive headlamps only illuminate the field of view in front of the vehicle, improving driver visibility in dim light and bad weather conditions. The low beam illuminates a short range in front of the vehicle, while the high beam has a longer beam distance and wider beam angle. For a long time, headlight systems have followed this design pattern, and with the advancement of technology, headlight systems are undergoing major changes.
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By Brian Ballard, Texas Instruments
To eliminate glare in headlamp high beam systems, designers can now employ pixel-level digital control.
Traditional automotive headlamps only illuminate the field of view in front of the vehicle, improving driver visibility in dim light and bad weather conditions. The low beam illuminates a short range in front of the vehicle, while the high beam has a longer beam distance and wider beam angle. For a long time, headlight systems have followed this design pattern, and with the advancement of technology, headlight systems are undergoing major changes.
In the 1950s, American automakers began installing two enclosed headlamps at the front of the vehicle, which eventually evolved into the vehicle’s high-beam and low-beam systems. Fast forward to 2018, and the headlight systems in vehicles are more complex. Light-emitting diode (LED) light sources are replacing traditional halogen and xenon bulbs. LEDs are likely to completely replace xenon lamps in the short term and halogen lamps later, as automakers move from static incandescent bulbs to more flexible and stylish LED lamps.
Sadly, despite decades of development, the National Highway Traffic Safety Administration (NHTSA) reported that about 30 percent of crashes in the United States in 2015 occurred at night.1IHS Markit reports that 50% of accidents in the United States are due to low vision; this number is bound to continue to increase as the population ages.
According to a survey by the Technical University of Darmstadt, Germany3, In terms of vision, older drivers tend to experience various types of vision degradation, including decreased visual acuity, miosis, and slower adaptation to the dark. People between the ages of 60 and 65 need twice the illumination and contrast and half the glare load to achieve the level of vision a 25-year-old would have.
Although glare from high beams can be distracting and even temporarily blind, glare prevention has historically been done by the driver, with switching between high and low beams the only means of control. Therefore, in reality, the driver often has to operate the headlight pole: switch the high beam when there is no oncoming vehicle, and turn off the high beam when other vehicles appear.
How can the driver keep the high beams on while driving the vehicle to improve visibility?
Figure 1. An example use case for adaptive headlight (ADB) technology. (Source: Texas Instruments)
Adaptive headlights (ADB) (Figure 1) combine advanced driver assistance systems (ADAS) with external lighting systems to achieve this functionality. In addition to ADAS technology, Texas Instruments (TI) now offers DLP chipsets that enable more granular control of automotive headlights through ADB technology, enabling automakers and Tier 1 suppliers to individually Control over 1 million pixels. With this technology, headlights can go out in areas that affect the vision of other drivers or pedestrians, and can even be programmed to map road information, such as lane lines or route guidance.
Micromirror
The core component of a DLP chipset is a set of aluminum micromirrors called a digital micromirror device (DMD). Depending on the specific configuration, a DMD can contain hundreds of thousands or millions of individually controlled micromirrors, each built on top of an underlying CMOS memory cell.
Each mirror is fitted with a flexible mechanical support structure that allows the mirror to be suspended from the two addressing electrodes. These electrodes connect to the memory cells and generate complementary electrostatic forces that position the mirrors in one of two stable landing states.
When integrated into an optical system, a DMD is a symmetrical two-state optomechanical element, so the position of the micromirror for each landing state determines the direction of incident light reflection. The high operating frequency and small pixel size of the DMD enables high-speed modulation and low system latency, which in turn improves the precision of headlight control and enhances the driver’s visual visibility.
Systems that support DLP technology can be used with any light source, including LED, laser/phosphor, and direct laser illumination sources. Compared with existing ADB solutions, it can be designed as a lighting system with less power and volume, and a more stylish appearance. DLP technology is also efficient and scalable, while providing better beam control, improving viewing distance and visibility in low light conditions.
Either dim individual LEDs in the light, or move the beam down or to the side of the opposite lane, compared to comparable anti-glare high beam solutions. Some solutions switch between high and low beams, while others rotate the beam as the vehicle turns. In effect, what these systems do is turn off or block the light from the headlights, blocking oncoming vehicles or vehicles ahead to avoid glare. Typically, LED matrix solutions reduce glare to oncoming vehicles by turning off some of the LED lights.
While automatic on/off with predefined discrete beams is a good idea, this capability does not achieve the level of control required to develop beams with real-time adaptability. This resolution and adaptability facilitates ADAS functions such as traffic sign lighting for traffic sign recognition. This capability is necessary given the direction of semi-autonomous and autonomous driving in the automotive industry.
2. ADB technology can be used to improve the visibility of road signs. (Source: Texas Instruments)
The benefits of DLP technology in high-resolution headlamp systems include reducing glare on objects such as pedestrians (Figure 2) and drivers of oncoming vehicles. Minimize the time from sensor sending information to headlamp response (system latency), enabling high accuracy by providing higher pixels per viewing angle. In turn, it enables more luminous flux in the system, i.e. increasing the amount of light that can be controlled and hit the road surface. With low latency, complex AI-based predictive algorithms are no longer required to determine where an object will move next.
The DLP technology-based system uses additional sensor input to turn off the portion of the headlight projected onto the windshield of the oncoming vehicle so that the glare does not cause discomfort or distraction to the driver. The use of DLP technology in the headlight system allows fine-grained control of the pixelated headlight beam, enabling adaptive high beams, which help improve visibility and comfort during nighttime driving. Figure 3 shows an example of a system block diagram employing a DLP chipset in a headlamp system.
3. System block diagram using DLP chipset. (Source: Texas Instruments)
The DLP5531-Q1 chipset for high-resolution headlamp systems (Figure 4) provides engineers with a small-footprint system design that can customize the illumination spot for more precise control of light distribution on the road. The system can also partially or fully dim individual pixels, enabling extended use of high beams without affecting other drivers.
4. The DLP5531-Q1 chipset developed by Texas Instruments can be used in high-resolution headlamp systems. (Source: Texas Instruments)
Future uses of headlamp technology
Many automakers and tier 1 suppliers are very focused on the many benefits of increased visibility, while at the same time DLP technology is programmable. Therefore, it can be configured with new functions required for semi-autonomous and autonomous vehicles.
DLP technology for headlamp systems can be used in conjunction with ADAS to cast just the right amount of light at a specific location, such as a traffic sign, to help drivers clearly identify the sign. It is capable of projecting images and signs onto the road ahead, such as lane markings or navigation directions, enhancing communication between drivers, pedestrians and other vehicles. This feature will become increasingly important as the automotive industry evolves.
Headlight systems using this technology can enhance vehicle-pedestrian communication by being programmed to provide a signal or sign to pedestrians and indicate to the vehicle what to do next. Additionally, dedicated lane markings and car-to-driver enhancements such as symbol projection and Display of driver-related information (eg: navigation support, vehicle trajectory) are important considerations for future vehicles.
Additional Specifications
The DLP5531-Q1 chipset enables over 1 million addressable pixels per headlamp. It can operate under any light source, including LEDs and lasers, and operates between -40°C to 105°C, enabling clear image visibility regardless of temperature or polarization.
The Links: VUB145-16NO1 CM100TJ-24F INFIGBT