Handheld laser rangefinders have been available to consumers for years, but increasingly powerful military and industrial versions of the technology are still being developed. A new breed of LIDAR (light detection and ranging) technology is being developed and tested by the US Air Force at a base in Massachusetts. This system is capable of precisely mapping over 300 square kilometers from the belly of an airplane in about half an hour.While it is considerably more advanced than consumer models, the new Air Force LIDAR works on the same basic principle– laser light is projected toward the target, and a sensor detects the photons upon their return. The time it takes is used to calculate the distance, to varying degrees of accuracy. In advanced systems like those used by the military, LIDAR can create a topographic map of the area it is pointed at.
LIDAR has been used for aerial mapping of disaster areas and remote archaeological sites, but the process has always taken time. After the Haiti earthquake in 2010, a system similar to the one being developed by the Air Force was able to capture a 600 square-meter section of Port-au-Prince at 30cm pixel resolution in a single pass. The chip at the heart of the next generation system is about ten times more powerful.
The Air Force system makes the process a snap by packing an unprecedented number of single-photon pixels detectors into the microchip at the core of the unit. The key to the LIDAR’s incredible speed and resolution is semiconductor technology based on indium gallium arsenide (InGaAs). These III-V semiconductors (so-called because they are made from metals in periodic groups III and V) are seen as a potential replacement for silicon in numerous applications. In this case, InGaAs semiconductors operate in the infrared spectrum, which allows for the use of longer wavelengths of light that can travel farther and scan wider areas.
InGaAsWhile these new systems are still secret, the results from chips of the type used to map Port-au-Prince are beginning to make it into industrial applications. Princeton Lightwave and a division of Boeing have both been working with single-photon InGaAs LIDAR that could one day be incorporated into automated vehicles like Google’s self-driving cars.Current LIDAR systems are huge and are based on visible light and silicon. That means to see more than a few meters a system would need to be uncomfortably bright. Of course, InGaAs-based LIDAR has to come down in price first — Princeton Lightwave’s current industrial model costs $150,000, but it’s the size of a shoebox.
Princeton Lightwave is already in talks with car manufacturers to build a prototype LIDAR system that could point the way to the future. The military LIDAR capable of mapping cities in mere minutes won’t be much use to consumers, but it might come in handy for the greater good the next time there’s a natural disaster.
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