Laser, Lidar Is The Way Forward For Automotive Vision

Written by  Sameer Kumar | 14 March 2017 | Published in March 2017 ( Technology )

Globally, more than one million vehicle-related fatal accidents take place every year, along with more than 20 mn crash-related injuries. Costs for this mayhem are estimated to be more than Rs 200 lakh crore – a sum that's hard to even comprehend for most people. Of the many initiatives being undertaken by car manufacturers towards trying to enhance safety, and reduce the number of accidents that happen worldwide every year, one important initiative is increasing night-time visibility for drivers. Automotive lighting systems have already witnessed significant advancements over the last two to three decades, and further development continues relentlessly. We take a look at some cutting-edge developments in this space.

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LIGHTING EVOLUTION

Automotive lighting started with carbide-acetylene lamps in the late-1880s, moving to full electric lighting in the early-1900s. Sealed beam headlamps (the kind used today), with a lighting filament, parabolic reflector and a lens sealed together came in the late-1930s, while the much brighter halogen headlamps started appearing on some European cars by the early-1960s. The next big move came about in the early-2000s, when high-intensity discharge (HID) Xenon lamps were introduced on some high-end cars. Xenon/HID lamps produced light by creating an electrical arc between two metal electrodes, through an inert gas, inside a glass bulb. Much more efficient than traditional bulbs, HIDs created brighter, more intense 'white' light while consuming relatively lower amount of power. These were also physically smaller, providing more design flexibility to car manufacturers in terms of shaping a car's headlamps. However, there were issues with HID lamps 'dazzling' oncoming traffic due to their intense light getting 'scattered' by traditional light assemblies, and manufacturers started looking for better solutions.

One solution, which is now finding widespread use not just in higher-end cars but also on relatively cheaper vehicles, is light-emitting diodes (LEDs), with the Audi A8 being the first production car to have LED daytime running lights (DRLs). While LEDs were initially used only in DRLs, costs have come down over the last five years and many OEMs are now increasingly opting for full-LED illumination on their cars. In fact, the 2007 Audi R8 was the first production car to use full LED illumination, with the Mercedes-Benz CLS following suit.

The problem of dazzling oncoming traffic has also been resolved with LED headlamps, with adaptive lighting technology that uses multiple individual LEDs in each headlamp unit. This allows intelligent focusing, with the system being able to dim or switch off only those individual LEDs that may be pointing at an oncoming vehicle. Some systems even allow LED lighting systems to work in conjunction with the car's onboard sat-nav, 'recognising' curves in the road in advance and directing light accordingly, just before the driver starts moving the steering wheel to follow the road.

LEDs are long lasting and users can, in most cases, expect their car's LED lights to last as long as the car itself (as compared to Halogen light bulbs, which typically have a total life of about 1,000 hr), without ever requiring replacement. Also, white LEDs offer about 6,000 K in terms of their colour temperature, meaning that the light's intensity is about the same as regular daylight, which helps in the way the human eye sees a road lit up by an LED headlamp since the illumination appears more natural.

LASER ILLUMINATION

While many OEMs are just about beginning to move from using only LED DRLs and adopt full-LED lighting, the world of automotive lighting technology has already moved on to laser. Taking the lead away from Audi, the futuristic BMW i8 was the first production car to be equipped with a full laser lighting system, which worked via three diodes shooting blue laser beams into a prism, with the latter then focussing the three beams into one unified beam. The unified beam is then passed through a phosphorous lens, transforming the light from blue to white, and then directing that white beam of light on to the road via a reflector. Laser lights have their advantages and disadvantages. They are up to 30 % more efficient than LEDs and have up to twice the illuminating range, but are not as focused as LED lights. Hence, for now, laser lights are only used for high beam lighting, while low beam illumination is still handled by LEDs.

In addition to BMW (which followed up the i8 with the new 7 Series, which also has laser lighting), Audi also used laser lights for its limited-edition R8 LMX supercar. The LMX's laser lighting system uses four diodes as compared to the i8's three and, according to Audi, its colour temperature (at 5500 Kelvin) is better suited to the human eye and provides better overall visibility. However, regardless of whether they're fitted to BMW or Audi cars, laser diodes are physically much smaller than LED systems and are able to provide light that's four times as bright as that produced by LEDs. Developed by OSRAM Speciality Lighting, the laser lights used on the BMW 7 Series have a range of 600 m, which is twice as much as most LEDs' illumination range.

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BEYOND LIGHTS

Yes, with LEDs and lasers, automotive illumination has come a very long way from where it was a few decades ago. However, there is more to come and OEMs are preparing to push beyond mere lighting systems. Leading up to autonomous cars in the future, vehicles equipped with 360-degree camera and radar systems will be able to 'see' and sense their surroundings, and will be able to navigate and react to obstacles in the driving path. The first step in this direction is the use of automotive-spec Radar systems, which use a transmitter that radiates radio waves, and a receiver that collects the waves reflected/ bounced back by surrounding objects. Studying changes in the speed and angle of deflection, a Radar system can 'see' a car's surroundings, though most existing systems suffer from limited range, field of view and resolution. This is partly because automotive Radar systems are smaller units, primarily designed to blend in with a car's exterior styling. Still using data from existing Radar systems, a car's on-board navigation system can implement some basic autonomous driving functions, such as braking automatically to avoid hitting another vehicle or pedestrian.

The next step in extending automotive vision, alongside Radar, will be the use of forward-facing and/ or 360° cameras, which will again be able to 'see' the car's surroundings and help the car navigate, at varying degrees of autonomous functionality. Such camera systems help with reversing, parallel parking, cruise control, lane keeping, automatic braking and, in the future, may also help with overtaking manoeuvres. Major companies like AutoLiv, Valeo, Delphi, Bosch and others are already developing vision-based ADAS systems and some will, in the near future, provide full-range camera hardware systems for automotive use, which will be capable of processing complex algorithms based on extensive databases, for partial or fully autonomous driving in all conditions.

A further advancement in this area is light detection and ranging (LIDAR) systems, which use infrared laser light for 3D scanning of a vehicle's surrounding environment. Single-laser LIDAR systems emit a narrow laser beam and collect information only for a narrow field of view, but newer systems are able to achieve a 360° horizontal field-of-view depth map around a car, by using a mechanical, rotating system that rotates the laser in all directions, thereby gathering information from all directions. Such systems are currently undergoing extensive testing and are expected to find their way on to mainstream production cars in the next 5-10 years. These systems still have various challenges to overcome, including low vertical resolution, low refresh rates (partly due to low rotating speeds of the mechanical device that rotates laser beams in all directions) and compromised performance in rain, snow and fog etc.

CONCLUSION

Going forward, it's clear that while increasingly sophisticated lighting systems will help the driver see better, it's solutions like cameras, Radar and LIDAR that will allow the vehicle itself to see and sense its surroundings and react accordingly. This may sound a fanciful imagination for now, but with major vendors and suppliers already working closely with OEMs for developing such systems, automotive vision will only get better in the years to come.

TEXT: Sameer Kumar

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