Clever software and small sensors control headlights

Written by: Tom Shelley | Published:

Tom Shelley reports on the technologies behind the latest smart car headlamp controls systems

Systems have, for some time, been available to switch car headlamps automatically between low and high beams in response to external lights. These systems are now becoming available on an increasingly wide selection of cars.

Using simple camera chips and 8bit microprocessors, these modest systems can decide unambiguously whether the lights seen are car head or tail lights, street lights or something else.

The approach is based on making clever and rapid choices in software, accessing large external databases of different kinds of lights and situations. The systems offer a number of lessons to designers of industrial vision systems.

The SmartBeam system, developed by Gentex, makes use of cameras with 40,000 to 64,000 pixels. Fixed on the forward looking side of the rear view mirror, the system captures five to six frames per second and links with an 8bit NEC microprocessor on a circuit board within the mirror housing.

The system, called High-Beam Assist (HBA), dips the car's headlamps when it detects oncoming car headlights, tail lights or more than two successive street lights.
Lights are turned back onto high beam in their absence. This is happens more quickly than can be achieved by a human driver.

Robert Steel, vice president for sales and marketing in Europe, explained the system accomplished this by using a series of 'tricks'. These include identifying street and building lights on the basis of their 50Hz flicker and studying the colour balances of different kinds of lights. Decision making is based on the study of digital camera recordings made in different countries, leading to a database that Steel described as 'terabytes in size'.

Gentex offers cameras and suitably equipped rear view mirrors, which can also be equipped with autodimming to reduce dazzle, and bright LCDs to show views from rear facing cameras during reversing.

Gentex works closely with headlamp and automotive manufacturers. Should information about speed, uphill and downhill attitude and turning be available on the vehicle's data bus, this could be incorporated into the headlamp control logic.

At present, the HBA system switches headlights between low and high beam, but the company also has a Variable Forward Lighting system on trial in which the low beams are raised on downward slopes and extended during fast driving on motorways, but lowered for driving in town or uphill.

This is to be succeeded by a more sophisticated system called Dynamic Forward Lighting, in which moving shutters within the headlight assembly cut out parts of what will, at all times, be a high beam. This will allow, for example, the road ahead to be fully illuminated, with sections cut out to accommodate other cars, whether in front or approaching. Gentex believes this might require a 200,000 pixel camera capturing 30 frames per second, but this would still be more modest than common industrial and military vision systems.

Much research has gone into the latter over the years, with schemes that involve massive processing power to undertake multiple fast Fourier transform calculations. Something that could use 'tricks' to pick up and identify, say, gun flashes or the reflection from the front of an incoming RPG round could be a lot more useful.

Pointers

* System uses 'tricks' to identify different kinds of lights, allowing headlights to be dipped in response to headlights, taillights or in urban driving, but to be switched to high beam elsewhere.

* The cameras are small and the processing power modest

* More sophisticated systems are being developed, but these will also require camera chips and processing power that are modest compared with those in use in mobile phones


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