Science News

Million frames a second camera

Sun, 1st Nov 2009

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There are many processes in physics chemistry and biology which are very interesting but happen very quickly so they are hard to study. There are many forms of high speed imaging but they work by making conventional cameras faster, which normally involves expensive mechanical systems and they often have a limited light sensitivity because their exposure time is so short. So if you are not careful you have to illuminate the sample so brightly that the light levels will damage it, and they are useless if you are looking at light emitted by a process.

The Megaframe project had just built a camera capable of 1 million frames per second Nerve_cellsby approaching the problem from a different direction. They have taken sensors called Single Photon Avalanche Diodes, which, as the name suggests, can detect individual photons, making the camera far more sensitive than a converntional camera. These detectors are then connected to timers which can tell you when the photon arrived to within 100ps and be ready to receive another photon 32ns afterwards. They have then made arrays of these detectors up to 128 square, which is a long way from HD video, but immensely better than the alternative of using individual detectors.

The precise measurement of when each photon gets to the detector makes this camera particularly means that it can be used for a variety of forms of imaging which need to know very precisely when the photons arrive at your detector.

This makes the camera useful in a variety of ways, not least, because the rate that Nerve Cellsome dyes (Oregon Green Bapta-1 ) emit light after they have been given energy by a laser is dependent on the concentration of calcium around them. Calcium is used in the firing of a nerve cell so this means that they have been able to make a video of an indivdual nerve cell firing and as they get more pixels on their detectors, they should be able to video groups of cells interacting.

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