By Ramesh Raskar and Christopher Barsi
High-speed imaging is a long-standing goal in optics, with applications in spectral dynamics, motion analysis, and three-dimensional imaging. Currently, commercially available systems can offer sensors operating at one million frames per second at reduced spatial resolution.1 In the lab setting, serial time-encoding of 2D images have provided 100 ps shutter speeds.2 Recently, researchers at the MIT Media Lab, in the Camera Culture group, led by Professor Ramesh Raskar, have developed a camera system that has an effective time resolution of 2 ps, roughly one half of a trillion frames per second.3
Raskar’s system is centered on repurposing a well-known device called a streak sensor, which is capable of recording 2 ps time scales, and an ultrafast femtosecond Titanium: Sapphire laser. In this system, the laser illuminates a scene of interest, and the streak sensor records the scattered light. Unfortunately, on its own, the streak sensor has several drawbacks. First, with an effective exposure time of 2 ps, the signal-to-noise ratio (SNR) is incredibly low, and any scattered light would be buried in noise. Second, the streak sensor itself has a one-dimensional aperture, so that it can image only a single horizontal line of a scene. Third, given the time resolution, a mechanism must be in place to synchronize the laser with the detector.