According to reports by the U.S. National Highway Traffic Safety Administration (NHTSA), approximately 30% of all car accidents in 2015 occurred at night in the United States. Yet, as rapidly as cars are advancing with the rise of advanced driver-assistance systems (ADAS), one thing that has remained relatively unchanged in American cars over the past 50 years is headlight technology.
A high-level overview of ADAS. Image used courtesy of First Sensor and TE Connectivity
Other countries, including China, the E.U., and Canada, have not fallen victim to this same stagnation. A new technology called adaptive driving beam (ADB) has proven a marked improvement over conventional U.S. lighting technology. Strangely, a 1967 U.S. regulation, which prohibits low and high beams from operating at the same time, is the single factor keeping this technology off U.S. roads.
In this article, we’ll discuss what ADB is, improvements in the field, and the U.S.’ status in ADB investment.
Adaptive Driving Beam (ADB) Technology
Driving at night can be dangerous if you’re in low-lit areas or inclement weather conditions. You might be tempted to keep your finger on the high beams at all times, leaving them on when the road is empty and switching them off when another car appears.
ADB technology is a new type of headlight that can selectively steer the headlight beam to allow you to drive with your high beam headlights on at night without blinding other drivers on the road.
ADB technology allows high beams to stay on without blinding oncoming vehicles. Image used courtesy of Mazda
There are many different methods of achieving this technology, but one of the most basic methods involves an array of LEDs. This method consists of a sensor that can determine the position of other vehicles on the road and uses this information to selectively control an array of millions of LED “pixels” to beamform the light output.
Samsung’s New PixCell LED for Headlights
Samsung’s PixCell LED chip. Image used courtesy of Samsung
The technology consists of individual LED segments that can be monolithically integrated—up to 100 LED segments into a single chip. Each LED segment functions as an individual pixel, turning on and off to appropriately steer the light beam, and is separated by silicon walls.
Samsung PixCell LED. Image used courtesy of Samsung
According to Samsung, its new technology helps to minimize area to 1/16th the size of conventional discrete LED modules used for ADB. This allows more freedom when designing headlamps and integrating more lighting into the same headlamp area.
Digital Light Processing (DLP) Chips Control Light Direction
One critical component of ADB systems is digital light processing (DLP) chips, which include thousands of individually-controlled digital micromirror devices (DMDs) built atop a CMOS memory cell.
Upheld with mechanical support, each of these reflective mirrors is raised over two electrodes connected to the memory cell. To maneuver the mirror into two potential stable landed states, these mirrors create complementary electrostatic forces. In an optical system, DMDs—known for their small pixel size and high operating frequency—control the direction of incoming reflected light.
Block diagram of including a DLP chipset. Image used courtesy of Texas Instruments
DLP-based headlight systems can flexibly operate with any light source, from direct laser illumination to LEDs, and are designed for high-speed modulation, low system latency, efficiency, and scalability—all key features of ADAS technology.
An Optical Scanner for ADB Systems
Recently, researchers from Japan have created a microelectromechanical systems (MEMS) optical scanner to enhance ADB systems. This scanner uses the piezoelectric effect to produce mechanical vibrations in the scanner in time with a laser diode.
The scanner will then steer the blue laser light beam toward a phosphor plate to create structured light, which converts into bright white light. The light intensity is controlled by the ADB controller depending on vehicle speed, traffic, and steering wheel angle.
MEMS optical scanner overview, including (a) a system block diagram and (b) its installation in the headlamp block. Image used courtesy of Asari et al.
One key feature of this scanner converting the beam to white light is that it reduces heat in the ADB system.
The researchers designed this scanner on a single chip using a bonded silicon-on-insulator wafer with a PZT layer created on it. This wafer was then laminated with metal to make piezoelectric actuators arranged like suspensions, allowing large-angle horizontal and vertical deflections. The result was 2D scanning of the headlight beam.
Images of the MEMS optical scanner. (a) Chip overview and (b) close-up of the bending corner of the suspensions. Image used courtesy of Asari et al.
The scanner also includes modes that prevent it from reacting to low-frequency noise and to account for temperature variations. This module represents one possible way that ADB technology could be easily implemented within consumer vehicles if the U.S. were to remove its current headlight regulations.
ADB in the U.S.?
The regulation that disallowed simultaneous operation of high and low beams, Federal Motor Vehicle Safety Standard No. 108, may have made sense at the time of its inception; however, automobiles have significantly evolved since then.
The consensus is that this regulation is antiquated and is holding the U.S. back from advancing ADAS technology that could potentially prevent millions of accidents. With increasing pressure to keep the U.S. at the forefront of automotive technology and driver safety, it may only be a matter of time until this regulation is lifted and ADB technology can come to the U.S.