The base block of the PIXIRAD imaging sensor is realized by coupling, with the flip-chip bonding (bump-bonding) technique, an X-ray sensor to a matrix of 512×476 microcircuits (CMOS ASIC). The sensor can be made of a thin layer of 1) crystalline Cadmium Telluride (CdTe) in Schottky or ohmic contact configuration, 2) crystalline Silicon, 3) Chromium compensated single crystal Gallium Arsenide (GaAs). The detector is able to count the X-ray photons transmitted through the object and converted in each pixel of the CdTe sensor in two energy bins in a single exposure.
The system therefore has a hybrid architecture in which the sensor and readout electronics are manufactured and processed separately. The sensor is segmented with the same ASIC geometry.
Starting from the base block, a complete imaging system is obtained by coupling a number of blocks along one direction and then operating in slot-scanning imaging mode or, in near future, along both directions, and operating in full-field imaging mode.
In the X-ray imaging sensor market PIXIRAD is an innovative, high quality system being:
noise free, due to the photon counting technique
with optimal values of contrast and spatial resolution
with high frame rate (>150 frame/sec)
with capability to separate the image in various color components depending on the incident radiation energy
- with capability to operate in dead-time free mode (reading one counter while taking data in the other one)
PRINCIPLE OF OPERATION OF PIXIRAD