Ever since the invention of the digital camera, new imaging applications have been explored. The increasing possibilities of fast digital cameras have resulted in applications that were unthinkable only twenty years ago. High-speed cameras nowadays are widely used for recording of dynamic events at high frame rates (e.g. 10000 fps). The results can then be inspected by playing individual frames at a lower speed.
High-speed imaging up to 100000 fps is easily feasible with current technology. But what if you need to create high-speed images when light conditions are far from optimal? Your high-speed camera will be no good under these circumstances, as a certain brightness of the object is required for the high frame rates that are used. The lack of light in combination with short exposure times will result in underexposed and noisy images. The obvious solution would be to increase the illumination level of the object. However, in some cases it is just not possible to add more light, for example because:
- The object to be recorded generates light by itself. This may be the case for phenomena like the combustion process (flames and turbines), or in living cells that emit fluorescent light.
- The radiation level corresponding to the required brightness would cause an unacceptable temperature rise of the object.
And what if the image signal has become too low because of the high frame rates? Camera noise will be an additional problem then. Fortunately, there is a high-tech solution for these problems: the image intensifier. It is used to intensify the image before it is projected onto the image sensor of the high-speed camera. The intensified image results in a sensor signal that is typically 10 000 times higher than without using an image intensifier—in the process elevating the signal above camera noise level.