Method and apparatus for reducing noise in a radiation capture device

摘要

The detector comprises a radiation detecting element (10) with a radiation sensor (12), a read-out module (20) and a control signal source (34). The read-out module (20) comprises a charge accumulator (14) and a read-out switch (16), an amplifier (22) including a reset/enable switch (24), a first sample and hold circuit (27) and a second sample and hold circuit (31). The sensor (12) causes a charge whose magnitude is proportional to the intensity of the radiation to accumulate in a capacitor (14). The accumulated charge is read out by transferring it to the read-out module (20). To read out the storage charge, the signal generator (34) sends an enable pulse which actuates switch (24) and sets it to the off-position. This enables integrating amplifier (22) which now begins to integrate any charges appearing at its input. Thereafter, signal generator (34) sends a first sampling pulse that actuates a switch (26) for sampling the output of integrator and storing it in the first sample and hold capacitor (28). A second pulse delivered from signal generator (34) causes a transfer of all charges stored in capacitor (14) to the integrating amplifier (22). The sample and hold circuits (27,31) store the output of the integrator (22) at the time of the end of the sampling pulse. Thus, any noise due to the initiation of this pulse is also stored in the first sample and hold circuit and would also appear with the radiation data signal. Both output signals containing noise components are subtracted from each other which results in a radiation data signal substantially free from enable/reset switching noise.