Cutting headlight glare

The dangers posed to drivers by glare could be alleviated by a device being patented in the US.

Glare caused by bright sunlight or the sudden appearance of another car’s headlights is distracting and is thought to contribute to a significant number of road accidents each year. It is particularly hazardous for older people, whose eyes take longer to adjust to the intensity of light.

The system under development at Reveo, a research and development company in Elmsford, New York, is an eye-tracking camera and a liquid crystal display (LCD) which could either lie across the windscreen or drop down when required.

When excessive light that could cause glare is detected by a sensor on the vehicle, data is sent to a computer processor. This works in conjunction with the eye-tracking camera, and via complex algorithms it decides which part of the driver’s field of view is most susceptible to the glare.

The device then selectively turns opaque the appropriate pixels in the screen, blocking out the extreme light while not obstructing the driver’s vision.

‘Depending on the application the pixels could have two states (opaque and transparent) or the pixels could allow a range of transparencies,’ said a company source.

‘The cost for this type of light attenuation panel will be drastically lower than for LCD panels intended for display applications, since far lower resolutions are requiredand coloured sub-pixels are unnecessary.’

Liquid crystals owe their properties to the alignment of molecules which, despite being randomly dispersed, all point in the same direction. The direction can be externally controlled by electric or magnetic fields.

Different types of LCDs, such as polarisation-based liquid crystals or ionic dye-based liquid crystals could be used in this application.

The Reveo device may also exploit Cholesteric Liquid Crystals (CLCs). These are crystals that arrange themselves into a 3D helix pattern – a property which allows light of certain wavelengths to pass through the crystals, while others are reflected back.

A version of CLCs devised by Reveo subsidiary Chelix has the additional attribute of shifting ‘pitch’. The turn and twist of the corkscrew shape can be varied, allowing more wavelengths of light to be filtered out than other ‘fixed pitch’ CLCs.

‘This material is almost completely transparent when no electric field is applied, yet is fully reflective in the presence of an electric field,’ said the source. ‘This property will reduce the possibility of the panel overheating through absorption when exposed to intense light.’

The current design is not yet finalised. Reveo’s engineers are considering whether the LCD screen would be best configured as a drop-down visor or a screen fitted to the windscreen itself. Another option is goggles or glasses.

Subject to agreements with manufacturers and car companies, a commercial version could be ready in two years.

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