X-ray technology is very important to non-destructive materials testing. The X-ray detector and the X-ray image are decisively important to the performance of this kind of testing technology. While, in the past, X-ray film was largely used as the imaging element, now, both in medicine and industry, digital X-ray detectors are becoming more and more common. Because the detectors themselves are exposed to X-rays during imaging, they must have a high degree of radiation stability to ensure good, consistent image quality.
Flat-panel detectors and conventional line cameras in industrial applications are irreversibly damaged after a short usage period due to the high levels of radiation and must be replaced. The X-rays are not completely absorbed by the scintillator and damage the semiconductor located directly behind it. This can be seen in such phenomena as pixel and gap defects or in multiple exposures of different images, known as image lag.
The X-ray detectors developed by Fraunhofer EZRT set new standards in radiation stability while retaining comparable levels of sensitivity and image quality. The functional principles is based on the visual mapping of a scintillator to semiconductor sensors. This allows all semiconductor elements to be shielded, even at very high energy levels. Another advantage is the simple implementation of detector formats and pixel sizes adapted especially for test purposes.
Detectors in the XEye series are available with an active surface of 200 mm x 200 mm and 400 mm x 200 mm. The local resolution can be set to 200 µm or 400 µm, depending on the application. At a local resolution of 400 µm, dynamism of better than 10,000:1 is achieved. Detectors with an active surface size of up to 600 mm x 600 mm are being planned. Pixel defects and image lag do not occur with XEye. The exposure time, which can be set as low as 1 ms, allows dynamic processes to be captured without blurring due to motion.
For scanning applications, the highly sensitive TDI line camera XScan was developed, which is available with a resolution of 125 µm to 1 mm and which allows an active measuring width of up to 1 m. The maximum line frequency is 3 kHz, which corresponds to an object speed of 1.5 m/sec at a local resolution of 0.5 mm. Compared with conventional line cameras, the TDI principle allows significantly better image quality at the same object speed.