A camera developed by scientists at the Massachusetts Institute of Technology under the direction of prof. Ramesha Raskara has enough speed to film a laser beam striking an object and its reflection. The researchers recorded very fast flashes of the laser, lasting 50 femtoseconds (femtosecond is one billionth of a second – PAP).
The fastest scientific cameras currently record images at a million frames per second. They work the same way as cameras sold on the consumer market – the main part is a CMOS converter that converts optical light into a digital form that can already be written to disk. The fastest camera developed by a team of researchers at the University of California operated at 6.1 frames per second and its shutter speed was 163 nanoseconds.
The MIT scientist’s camera is built differently. As a technology reviewer, Dr. Andreas Velten, a member of the engineering team, said that the response time was limited to 500 picoseconds in the camera system so that the electrical signal did not stay too long in the wires and chips themselves. The shutter speed is less than two picoseconds (the picosecond is the trillionth of a second) because the prototype was designed to “catch” the laser beam. For this reason, this camera also did not need special electronics.
The light coming into its optical part went to a special electrode – a photocathode – converting the photon stream into an equivalent electron beam. The electron beam was in turn on the back of the camera, covered with a chemical that glowed under its influence. This is almost exactly the same mechanism used in the recently produced cathode ray tubes of classic TVs.
Due to the fact that the camera was able to see only one line, MIT researchers have built a mirror system that allows full illumination and viewing of the entire image. The construction is also completed with a classic digital camera, which records the image at the back of the camera. These two records are submitted by the software in real time and form a homogeneous image, while the digital camera record only covers a small portion of the laser beam path, which is completely visible to the fast camera. The image resolution of the first prototype device is 500×600 dpi.
MIT’s built-in camera does not capture events that do not happen quickly and on a regular basis. This is a significant limitation in its application, however, Dr. Velten notes that its advantage, in turn, is the possibility of observing the previously impossible to grasp the moment of penetration and reflection of light in the plane or tissue.