System and method for detection, localization and signaling of single photon events and of at least two photons time coincidence events

A system for detecting events of photons comprising:

• at least one array of pixels, each pixel comprising a photodetector and a front-end electronics, which outputs a digital signal,
• the system further comprising at least one event detection electronics including:
• a plurality of digital-to-analog transductors, one for each pixel of the array, each digital-to-analog transductor configured to convert the digital signal coming from the respective pixel in a corresponding analog signal, which is quantized in amplitude and duration;
• an analog adder node, to which the plurality of digital-to-analog transductors is operatively connected, the analog adder node being configured to sum the quantized analog signals coming from the digital-to-analog transductors, thereby obtaining a sum analog signal;
• and
• an overall analog-to-digital transductor comprising:
• at least one first comparator and a second comparator, which are operatively connected to the analog adder node,
• wherein the first comparator is configured to compare an output signal of the analog adder node with a first threshold corresponding to the triggering, within a time coincidence window, of a number of pixels greater than or equal to a first predetermined value, and
• wherein the second comparator is configured to compare the output signal of the analog adder node with a second threshold corresponding to the triggering, within a time coincidence window, of a number of pixels greater than or equal to a second predetermined value, and
• wherein the first comparator and the second comparator are configured to output a digital signal if the output signal of the analog adder node exceeds, respectively, the first threshold or the second threshold, thereby allowing event detection, within the time coincidence window, with a number of photons incident on the array greater than or equal to the first or second predetermined value.

A method for detecting photon events, comprising the following steps, which are carried out in parallel:

• generating at least one digital signal upon the impact of a photon on one or more pixels of at least one pixel array;
• converting the digital signal coming from the respective triggered pixel in a corresponding analog signal, which is quantized in amplitude and duration;
• summing the quantized analog signals in an analog adder node, thereby obtaining an analog sum signal;
• converting an output signal of the analog adder node into at least two digital signals when the analog signal exceeds two threshold values, respectively;
• wherein the analog-to-digital conversion step comprises at least the steps of:
• comparing the output signal of the analog adder node with a first threshold corresponding to the triggering, within a time coincidence window, of a number of pixels greater than or equal to a first predetermined value;
• comparing the output signal of the analog adder node with a second threshold corresponding to the triggering, within a time coincidence window, of a number of pixels greater than or equal to a second predetermined value;
• and
• generating a digital signal when the output signal of the analog adder node exceeds, respectively, the first threshold or the second threshold, thereby allowing event detection, within the time coincidence window, with a number of photons incident on the array greater than or equal to the first or second predetermined value.