Earlier we explored the different ways that headlights produce light and how they stack up up against each other. In this feature we’ll look at some of the automated assistive technologies being incorporated into headlights and how they work.
Adaptive or directional headlights
Come hell or high water, regular static headlights point straight ahead. That’s fine in places with plenty of street lighting, but on dark, winding country roads these headlights may spend more time illuminating cane fields and the never-never than the road ahead.
Adaptive or directional headlights solve that problem by allowing the headlight projectors to swivel.
The car’s electronics track which way the car is heading by monitoring the car’s speed and rotation, as well as the angle of the steering wheel. Small electric motors are able to turn the headlight’s projectors by up to around 15 degrees to match the car’s intended direction. That way the headlights are almost always lighting up the road and any potential hazards that may lie there.
To prevent pedestrians and other road users from being blinded unnecessarily, most adaptive headlights systems don't start turning the projectors until a threshold speed has been breached.
Adaptive headlights are common on many cars with HID or xenon headlights today, but the idea actually come to prominence way back in 1960s.
Busting out of the post-World II straightjacket of austerity, the Citroen DS wowed the automotive world with its eye-catching aerodynamic styling and advanced tech, which included hydropneumatic suspension, front-wheel drive and an automated manual gearbox.
It also featured covered headlights for improved aerodynamics. Late in its life, the DS gained directional headlights. With that option box ticked, the DS had high-beam lights mechanically linked to the steering wheel. Turn the wheel and the headlights would follow your steering inputs.
Technological limitations, not to mention cost and legislative issues, meant that the idea never really took off until the recent rise of powerful on-board computers and cheap electrics.
Whereas adaptive headlights are designed to illuminate long, sweeping bends, cornering lights are meant to provide a bit extra brightness to help with sharp turns or parking.
Cornering lights generally only switch on at low speeds when the indicators are on, reverse is engaged or the steering wheel is being turned furiously.
To provide this functionality older cars employed a small side light, while modern vehicles generally employ a swivelling lens in the fog light or main headlight housing.
HID headlights are several times brighter than conventional halogen lights, and because of this they can easily stun and dazzle other drivers and pedestrians. This is especially true on hills, and when driving over bumps and dips.
That’s why in Australia and Europe cars equipped with these headlights are required by law to be fitted with a self-levelling system that attempts to keep the headlights pointing down at the road.
Typically a self-levelling system will determine the car’s inclination by monitoring the front and rear suspension. Electric actuators, not too dissimilar to the ones that move adaptive headlights side to side, are then able to quickly adjust the projector’s beam up or down.
Automatic or dusk-sensing headlights
Drivers have a lot of things on their minds: other vehicles, pedestrians, directions and heavy-handed speed limit enforcement. Deciding when to switch the headlights on or off is one thing that technology can easily take off their shoulders.
Dusk-sensing headlights typically use an ambient light sensor to measure the brightness of the surrounding environment. This sensor is usually hidden inside a little dome at the base of the windscreen, although some manufacturers install the sensors at the top of the windshield.
When the surrounding environment is a little too dark for a little too long, the sensor will instruct the headlights, as well as the instrument and dashboard lights, to turn on. Once brightness reaches regular daylight levels again it will turn the headlights and instrument lighting off. Simple.
Automatic high beam
On dark highways in the countryside it’s always a good idea to have the high beams on, as they can illuminate much further than low beams are able to. On a stretch of road that’s got a moderate amount of traffic, though, it can be a pain switching back and forth between low and high beam.
Automatic high beams usually operate via a camera-style sensor mounted on the front-facing section of the interior mirror. This sensor can detect street lights, tail-lights and the headlights of on-coming cars.
If the road is sufficiently lit by street lighting, the high beams stay off. On unlit or poorly lit roads the high beams stay on unless you’re following a car or there is oncoming traffic.
Selective high beam filtering
Forward facing cameras and radar play an important role for many safety systems, and they're often utilised to track vehicles at night for the benefit of selective high beam filtering systems. Essentially, the aim is to stop your car's lights from dazzling other road users.
Once another vehicle is calculated to cross your car's high beam, the system can begin calculating how to alter the beam pattern to accommodate it.
The biggest hurdle for this type of technology is how to shade the area where other road users are. For projector-style headlights there are two methods for adjusting the high beam.
In the first, an object is moved around in front of the bulb to blank out the area where other cars are. This can lead to quite complex designs for systems that are able to cope with multiple vehicles in different locations without reverting to the dipped beam.
The second method uses the swivelling motors employed for the adaptive headlight and/or the self-levelling system. Some systems can splay one or both headlight beams slightly to shield a vehicle from the full might of your high beams. Other systems shift the headlights up and down the road depending on the presence or absence of other road users.
In the most advanced systems, a headlight features LEDs arranged into clusters, each of which can be individually turned on or off, and dimmed. This not only allows for low and high beam patterns, but also enables the headlights to dim certain portions of the road ahead to cater for other vehicles. This is the approach taken by Audi's Matrix LED headlights and Mercedes-Benz' Multibeam LED headlights.