A new version of a remote sensing technology using lasers is now being tried out with a view to improving object detection and developing smaller, cheaper 3D imaging systems.
Lidar – an abbreviation for ‘light radar’ – technology works by bouncing light radar-style off objects in the vicinity. It can measure distance by hitting the target object with a laser beam and analysing the reflected light, and can even provide such information as the object’s chemical composition. Initially this remote sensing technology was used for aerial and geological mapping, but now researchers at the University of Berkeley, California have improved it by using a special type of semiconductor laser diode in combination with a microelectromechanical system (MEMS). While current laser-based remote sensing systems can only measure up to a metre, the new system can detect objects as far away as ten metres, according to Behnam Behroozpour, a Ph.D student working on the project. This new development should enable a wide range of more efficient three-dimensional imaging applications in areas as diverse as self-driving automobiles, smartphone control and interactive video games.
A MEMS-tuned VCSEL
The lasers currently being used for remote sensing and mapping purposes are large, power-hungry and expensive. Behnam Behroozpour explains that in order to get around these drawbacks the team has been using a new type of laser – vertical-cavity surface-emitting lasers (VCSELs). A VCSEL is a semiconductor laser diode whose special feature is that it emits the laser beam at a perpendicular angle from the top surface, unlike conventional edge-emitting semiconductor lasers, which emit the beam from a surface formed by cleaving the individual chip out of a wafer. This approach consumes less power. Next, in order to modify the laser frequency and strengthen the signal, the researchers are making use of MEMS – micro-machines made up of tiny components including a small central data-processing unit, powered by electricity – to activate the lasers when required. An added innovation is that the researchers are drawing on the natural vibrations of the MEMS to amplify the laser without allowing any light to dissipate. Once again this process reduces overall power consumption.
New applications down the road
The MEMS-tuned VCSEL will consume less power and generate more precise signals, enabling a more compact assembly. This gain in space has the potential to substantially improve the ergonomics – and thus enhance the user experience – of a whole range of electronic equipment. For example, in the near future a driverless car would be equipped to generate a highly precise image of a child in the street ten metres away. At the present time Google’s self-driving cars and Microsoft’s Kinect technology widely used in video games both use 3D cameras, which take up a large amount of space. The Berkeley team’s subsequent plans include integrating the VCSEL, photonics and electronics into a chip-scale package. Consolidating these parts should open up possibilities for “a host of new applications that have not even been invented yet”, says Behroozpour – such as answering your smartphone from across the room, at a distance of ten metres, with just a wave of the hand.