Systems of light detection and ranging type lidar are widely used in geodesy, atmospheric studies, to create active safety systems of vehicles. Such systems consist of a light emitter and a sensitive receiver. The directional signal from the source is reflected from the object is detected by the receiver, resulting in a response time can determine the coordinates of the object of interest.
However, these well-known systems
only suitable for tracking objects in the field of view of the observer. In recent years, scientists are working to develop systems that allow to detect objects hidden obstacles.
One way to look beyond the obstacle – the use of the scattered light. To better understand the mechanism of action, one can imagine the following situation: directly in front of the observer is an obstacle for them – the object to be detected, and the object – a wall. The observer directs the light beam on the wall, the light is reflected from it and scattered in the area of the barrier, reflecting including on objects of interest. This reflected light is detected by a special device. As shown in the recent research , with the help of such a system can not only detect the presence of the object out of sight, but also to build 3D-models of objects. However, this method requires a long time of signal reception and can be used for tracking objects in real time.
A similar approach to the problem has been recently suggested in an article published in the journal Nature Photonics . However, in this case
required place the light source from the object of an obstacle, which is not always possible and may hinder the practical application.
It was recently suggested another solution, which is the most promising in terms of practical application. A group of British physicists led Genevieve Garepi and Daniel Fassa from Universidad Heriot and Watt has created a system that determines the position and trajectory of the located around the corner of the object with an accuracy of about 1 cm. The article on this was published in the journal Nature Photonics .
Established scientists system consists of two main elements: the laser and camera-based single-photon avalanche diode . This camera has a high sensitivity (ability to detect single photons) and speed. As the light diffuser scientists have proposed the use of the floor surface.
On one side of the angle of the wall located facility – a figure human foam height of 30 cm. On the other side – the camera and light source (laser).
laser beam is directed onto the floor in front of the angle of the wall. The scattered laser light reflected off the figures and found himself in the scope of the camera. By analyzing the reflected light, and the response time scientists have calculated the coordinates of the object.
The proposed method allows to determine the location of a hidden obstacle object in real time, if the object is at a distance of 1 m from the camera. The system does not require any additional equipment, besides having sex for the scattering of laser light. However, the type of surface from which light is reflected, plays a role: the use of black cardboard increases the detection signal is five times as compared to white cardboard. However, as the scientists say, the system is quite suitable for use in the real world.
«We are already working with ordinary surfaces – concrete floors and walls – and not notice any significant difference. On other surfaces, such as sand, we have not worked, but I think the system will work, too, “- said” Gazeta.ru “Daniel Fass.
The average time of detection is about three seconds . Already the system is suitable for real-time tracking of a person moving at a speed of several kilometers per hour. According to Daniel Fassa, this camera will help in situations where it is important to look beyond the obstacle, but you can not get there directly: for example, the device can be used to create active safety systems of vehicles (which allows you to control the movement of the hidden around the corner of the object – another car or a pedestrian – and report the driver to avoid a collision). The camera will enable rescuers and firefighters to find people in the premises to which access is difficult, and also be able to help in the liberation of the hostages – rescuers will be able to understand at a distance, how many people are in the room.
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