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Laser and radar sensing: Long distance solutions

12 October 2016

An expert in the production of optoelectronics, Banner Engineering has an in-depth understanding both of the capabilities and the limitations of standard photo-electric sensors. Its expertise, however, is not limited to this type of sensor and here the company considers when it might be better to use a laser device over a standard LED photoelectric unit

Applications where light is required to travel great distances are generally solved using laser sensors. Both laser and LED use a diode to generate the light, in laser technology the laser then bounces this light back and forth within its housing to generate more of the same wavelength of light (monochromatic, single colour), and more critically all the waves are in line with each other (coherent). LEDs also generate near monochromatic light and have a broader spectrum of wavelengths than lasers. However, the critical feature is that the light is incoherent, the wavelengths are randomly produced.

All natural light and most man-made light is incoherent and has many wavelengths which is why it spreads out from its point source as it travels. Laser light remains in a tightly focused beam over great distances.

It is this coherence of laser light that gives laser sensors their unique property of a very narrow beam that can travel great distances without spreading out, making them especially suited for certain types of application and a poor choice for others.

Target materials and textures also play an important part in sensor selection. For example, Banner's LTF Series of laser distance sensors are designed to accurately measure targets at distances to 12m. They provide reliable detection regardless of colour or material. The dynamically adjusted laser power increases output for dark targets or objects at steep angles while reducing power for shiny ones, providing accurate measurements across a wide range of challenging targets.

Where does radar fit in?

All sensing disciplines have an 'Achilles heel'. For example, Banner says ultrasonic devices struggle to operate correctly in high winds as the sound wave emitted and received back to the unit can literally be blown off course, resulting in poor response. Similarly, many photo-electric sensors – when used outside – can suffer the effects of adverse weather – snow, fog, heavy rain and humidity. Even good weather can present problems as bright sunlight can affect correct operation. In addition a build- up of dust and dirt on the lens will impede accurate sensing. 

Radar sensors are unaffected by wind, rain, fog, light, humidity or air temperatures (operating temperatures are between -40 and +65°C). They use Frequency Modulated Continuous Wave (FMCW) radar to reliably detect moving or stationary targets and their reliability over long distances in extreme weather conditions make them a suitable choice for collision avoidance on-board mobile equipment such as reach stackers, forklifts, and mining vehicles.

The Q120RA range from Banner has a narrow beam pattern and will detect objects from 1 to 40m. It has two independently adjustable sensing zones and its robust construction make it suitable for port crane anti-collision and train detection applications.

By contrast the QT50RAFQ is a wide angle device with a total beam angle of 90°, suitable for use in traffic monitoring, car parking and road toll applications.

In the UK, Turck Banner can offer sensing solutions across all industry sectors. Furthermore, the comprehensive choice of laser and radar solutions lend weight to the company’s claim that, in the world of industrial sensing – distance is no object.