Time to digital conversion

A circuit for time to digital conversion, the circuit comprising:

• a time to digital converter, TDC, configured to receive trigger signals and event signals and, for each event signal, provide a time stamp indicative of a time period between the event signal and an associated trigger signal;
• a first memory unit for storing a set of time stamps associated with one trigger signal and provided by the TDC;
• a processing unit configured to compare the set of time stamps stored in the first memory unit to new time stamps provided by the TDC to determine coincident time stamps, and
• a second memory unit for storing a histogram comprising a plurality of time bins each representing a number of events, wherein the processing unit is configured to increment the time bins of the histogram corresponding to the coincident time stamps.