OPTOELECTRONICS FEATURE SENSORS SHED LIGHT ON SAFETY
Gualtiero Bagnuoli, from Melexis, discusses how the company’s MLX75305 series of light sensors are being used in the development of laser-powered lighting units for cars
A vital function that is needed for these systems is to be able to constantly monitor the output of the laser-powered lighting units to ensure that this is maintained at the correct level. The sensors utilised for this need should possess all of the following attributes in order to be successful: 1. Performance - These devices need to
have high degrees of accuracy, linearity and responsiveness. 2. Robustness - They must be able to cope with elevated temperatures, voltage surges, electro-static discharges, etc. 3. Cost effectiveness - This reflects the fact the automotive sector is incredibly competitive and bill of material costs need to be kept in check. 4. Compactness - Due to the limited space available in modern automobile designs any technology incorporated must have a small form factor. Engineers at Melexis are working together
O
ver recent years there has been growing uptake of more sophisticated lighting technology within the automotive sector. The use of LED emitters has proved to be beneficial and seen widespread deployment, for both internal and external illumination purposes. It has led to a marked lowering of the power consumption for lighting systems, while simultaneously offering greater breadth of functionality and supporting more extensive operational lifespans than were possible with conventional incandescent lamps (employing either halogen or xenon technologies). Further innovations are now emerging which could have even greater impact on the automobile business in the future. Incorporation of laser diodes into automotive front lighting has the potential to revolutionise road safety. This approach is already witnessing implementation - with certain high-end car models using this technology. It is likely that over time greater proliferation of laser-powered lighting mechanisms will occur and it will slowly move down from the luxury bracket toward mid-range models. The basic principles of laser-powered
‘Incorporation of laser diodes into
automotive front lighting has the potential to revolutionise safety’
lighting systems are as follows. Laser diodes in each lighting unit respectively deliver a beam of monochromatic (with a blue wavelength), coherent light. These beams are directed onto phosphorescent elements which convert them into white light with a high intensity. The main advantage of laser-powered front lighting is that it enables the brightness of the vehicle’s high beam to effectively be quadrupled, thereby extending the distance that is illuminated from around 350m to over 600m. This increased visibility, which is of particular value when travelling at speed, means drivers are alerted to possible obstacles/hazards that lie ahead much earlier, and have longer time to take any
action needed. As well as the increased
range that is achievable by laser-powered light, this approach is
also more energy efficient (around 30% higher) than LED lighting - which itself was already an improvement on the incandescent lamps still widely used in cars. Furthermore, it supports smaller form factors, giving vehicle design teams much greater scope when developing new aesthetically appealing models (as well as improving the aerodynamics).
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Housed in a compact 8-pin SOIC format package, the MLX75305 provides a rugged, single chip solution for headlamp output monitoring purposes
with automobile manufacturers, and their Tier 1 suppliers, to develop effective laser- based light monitoring systems using the MLX75305 series of light sensors. These devices are specifically optimised for installation into demanding automotive applications where they are exposed to harsh environmental conditions. Covering a spectral bandwidth of 500nm to 1000nm, these ICs maintain ±2% linearity across their whole output voltage range with a typical responsiveness of 70mV/(uW/cm2
).
Housed in a compact 8-pin SOIC format package, the MLX75305 provides a rugged, single chip solution for headlamp output monitoring purposes. The device comprises a photodiode, trans-impedance amplifier and output stage. The semiconductor hardware is straightforward to implement and requires just a few external components to accompany it - thus taking up minimal PCB real estate. Unlike competing ICs, this device is compliant with the AEC-Q100 standard and can support an operational temperature range that spans from -40°C up to +125°C. Though still in its early stages, it is clear
that there is great potential for vehicle front lighting based on laser technology. Through this car manufacturers will be able to improve driver visibility, without impinging fuel economy. Over time this will bring about enhancements in terms of road user safety across the globe.
Melexis
www.melexis.com T: +49 361 43026000
ELECTRONICS | JUNE 2017 31
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