Charged coupled devices (CCD detectors)

CCDs have become quite common in everyday life – this is the technology that records pictures in digital cameras, cell phones, and digital video recorders. If you have a cell phone with a camera, then you have a CCD!

CCDs are essentially solid state detectors; however, they are broken up into a grid of small detectors, called pixels. Each pixel is a solid state detector. When an X-ray hits a pixel, electrons are freed from the material through the photoelectric effect. These electrons are held in the pixel until the CCD is “read out.” Once the shutter has been closed (or essentially the CCD is “closed for business”), the device is read by a circuit that counts the number of electrons in each pixel. This is done one row of pixels at a time.