The leading detector technology, which Advacam uses for its products and solutions, is based on Medipix hybrid pixel detectors. These devices were developed with the international collaboration of universities and research laboratories led by the team at CERN during the past 20 years. Advacam’s team members have been part of the Medipix Collaboration from its inception and have been contributing to the technology.
Advacam’s imaging cameras are direct conversion single photon counting pixel detectors that represent the cutting edge technology of radiation imaging. The term “single-photon counting” means that every single photon of X-ray radiation detected in an individual pixel is processed and counted. The technology brings two major advantages in comparison to conventional X-ray imaging – high contrast along with sharp images and spectral information of X-rays that allows material-specific information to be displayed in colors.
In the direct conversion cameras, each pixel of the semiconductor crystal is directly connected to the complex CMOS circuit using a conductive solder bump. In the indirect conversion cameras, a scintillation layer is attached on top of a photodiode. The photodiodes manufactured on a simple CMOS circuit that enables fine pixel sizes.
The photon-counting principle of detection eliminates all other sources of noise that are present in CCD or flat-panel-based cameras. This leads to a considerably better signal-to-noise ratio and therefore detectability of more details in images. The image’s sharpness or the actual spatial resolution of the captured image is defined by the electric charge in the CMOS readout. Even though the pixel size of the direct converting cameras is larger than that of the conventional indirect conversion cameras, the signal of the detected X-rays is better focused on the pixels. The typical size of a direct conversion pixel ranges from few millimeters to tens of micrometers where Advacam represents the highest pixel density of the current industrial X-ray cameras with 55 um pixel size.
Energy sensitivity is an as important advancement of imaging technology as was the colour photography and film. Contrary to regular X-ray imaging cameras, photon-counting cameras can discriminate or even directly measure the energy (wavelength) of incoming photons. Since each element of the sample has different X-ray attenuating properties, it is possible to estimate the material composition of the sample if the energy of the photons is measured. The spectral sensitivity offers a major improvement over conventional X-ray imaging cameras.
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