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There are many ways to use lasers to process and improve materials. ■ Welding – focusing the laser beam onto the joint and melting the weld material fuses the two components to be joined. ■ Laser cladding – this is similar to welding, in that additional weldable material in powder form (such as stainless steel, steel, or aluminium) is melted onto a component's surface to apply a new layer with different properties onto an existing substrate. Components can be made more resistant to wear and corrosion, and the process can even extend the life of old components by building up worn areas. ■ Surface modification includes laser cleaning, corrosion prevention, and laser hardening. If you heat the surface of a steel component to a high temperature and cool it rapidly, for instance, the material undergoes a 'phase change' and becomes much harder. Lasers as a heating source make accurate localized heat treatment of components possible, because the beam is so controllable and precise. Laser pulses can also be used to remove layers of rust, paint, grease, and other unwanted contaminants from components or materials quickly and efficiently without damaging the original.
Clockwise (from top left): 1. An injection mould after wearresistant powder cladding and before final machining. 2. The selective laser hardening of a tool, which is done to increase its working life. 3. A thick layer of grease is removed by means of a transverse excited atmospheric (TEA) CO2 laser. 4. Yttrium aluminium garnet (YAG) laser cladding of a tool steel injection mould. New material is deposited on existing components to improve wear and reduce corrosion.
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Good, clean air
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The light detection and ranging (LIDAR) laser technology we probably know best is the device the police use to measure the speed of cars on public roads. But we also use LIDAR to measure air pollution, track wind and weather patterns, and monitor changes in the ozone layer. In fact, scientists are now considering space-based LIDAR systems to monitor the Earth's environment and changes in its atmosphere. LIDAR is a laser remote-sensing technique that works rather like radar – where radar transmits radio waves, the LIDAR transmits laser light. The system consists of a laser transmitter, a receiver telescope, photo-detectors, and data-capturing electronics.
How a LIDAR works. Laser light is transmitted in a specific direction or in multiple directions. It interacts with molecules (the target) in the atmosphere, and some part of the light is reflected or scattered back to the telescope, where it is measured by photo-detectors. The measured light goes through a data-capturing electronic system, from which we can deduce information about the altitude, the different types of gases in the atmosphere, and their concentration.
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