Image Intensifiers

An image intensifier is a device that converts an incident X-Ray image into a corresponding visible light image which can be subsequently detected with an analogue, or digital camera.

An image intensifier is constructed from a vacuum bottle, with a relatively large diameter X-Ray transparent input window at the front, and a smaller diameter glass output window at the back. Behind the input window an input scintillator converts a proportion of the incident X-Ray photons into a larger number of visible light photons. Directly behind the input scintillator lies a thin photocathode. When the light photons strike the photocathode a proportion are converted into photoelectrons. These electrons are then accelerated by a high voltage field towards the output window. When the electrons reach the output window they strike an output scintillator which converts the photoelectrons back into visible light photons. These then escape the image intensifier through the glass output window where they can then be imaged using conventional optics and cameras.

Despite the many interfaces from input to output window, the compression of the image size (typically in the order of 10 times or more) and the high voltage acceleration enable image intensifiers to produce images that are 5,000-10,000 times brighter than conventional fluorescent screens. This high sensitivity to X-Rays allow image intensifiers to be used in applications where very short exposures are required, as in the case of real time imaging (for example at 25 frames per second, with single frame exposure times of just 40ms).

Shaw Inspection Systems provide a range of integrated Image Intensifier and both analogue and digital camera solutions, from stand alone detectors, to fully integrated cabinet based X-Rays systems.