New ultra-high-speed camera allows to see the shock wave generated by the movement of light
Scientists from the University of Washington have developed and created a new ultra-high-speed camera capable of capturing the movement of a laser light pulse. Moreover, the new camera, which takes 100 billion frames per second, was able to see the “Mach cone” of light, the optical equivalent of the sound shock wave that occurs when a flying plane crosses the sound barrier. The presence of such a shooting technology will allow scientists to observe high-speed phenomena that arise, for example, at the moment of activation of brain neurons or when elusive neutrino particles collide with the nuclei of atoms of ordinary matter.
An airplane in flight creates a Mach cone at the moment when its speed increases, passing through a value equal to the speed of sound propagation, one Mach. Since the engines of an aircraft are sources of strong sound, and the aircraft travels faster than sound, the sound waves from the engines are superimposed on each other, compressed and propagated in space in the form of a cone, at the top of which the aircraft is located. And it turns out that the same thing happens when the light moves.
To ensure the conditions for the appearance of the optical Mach cone, the researchers made two panels of a silicone compound, which was filled with the smallest aluminum particles, the edges of which acted as mirrors reflecting light towards the camera sensor. On the border of the two panels, a channel was made filled with normal air. In addition, a fog created with a piece of dry ice was “mixed” into the air in the channel, which made the laser light pulse itself visible.
Since silicone has a different refractive index than air, light travels more slowly in its environment than in air. And when passing from silicone to air, the light is accelerated and passes the “light barrier”, which causes the appearance of the optical equivalent of the Mach cone.
Three cameras were used to capture images, one of which was a slit camera with a specialized CCD sensor. This method has been known for a long time and it allows you to shoot very fast phenomena, although the width of the image obtained at a time is only one pixel. In this case, the slit of the camera lens was widened and the cameras captured an image two pixels wide at a time.
A template filter was installed in front of the camera lens, with the help of which an image resembling a barcode was obtained in several passes. On the basis of this image, the computer, with the help of algorithms and complex processing, restored a complete three-dimensional picture of the processes taking place. The two additional cameras used a standard high-speed shooting method and their data was used to increase the resolution and quality of the final image.
Source: http://www.dailytechinfo.org/