Determining relative timing offset in different electronic pathways using internal signals

A timing delay detection method, comprising:

• outputting a signal from a detector that includes a photosensor;
• detecting an after-pulse in the output signal at a plurality of after-pulse detector devices independently connected to the photosensor via respective electronic pathways, the after-pulse representing an after-event in the photosensor triggered from a previous photon producing event;
• outputting, at the plurality of after-pulse detector devices, an indication when the after-pulse is detected;
• receiving, at a processing device, the indication of the detection of the after-pulse from each of the plurality of after-pulse detector devices;
• determining, at the processing device, relative delays between the respective pathways based on relative timing of the received indications;
• and
• storing each determined relative delay in association with an identification of a corresponding after-pulse detector device.

An after-pulse detector device independently connected to a photosensor via respective electronic pathways, the after-pulse detector device comprising:

• an integrator configured to receive a signal from the photosensor, to perform integration on the received signal, and to output an integrated signal;
• a first comparator configured to receive the signal from the photosensor and to compare an amplitude of the signal with a first reference value;
• a second comparator configured to receive the integrated signal from the integrator and to compare the integrated signal with a second reference value;
• and
• an AND logic gate configured to receive a first output from the first comparator and a second output from the second comparator and to output an indication of after-pulse detection in response to both the first output and the second output being logic level high.

An after-pulse detector device independently connected to a photosensor via respective electronic pathways, the after-pulse detector device comprising:

• an analog to digital (A/D) converter configured to receive a signal from the photosensor and to convert the signal into a digital signal;
• an integrating unit configured to receive the digital signal output from the A/D converter, perform integration on the digital signal, and output an integrated signal;
• a first comparison unit configured to receive the digital signal from the A/D converter and to compare an amplitude of the signal with a first reference value;
• a second comparison unit configured to receive the integrated signal from the integrating unit and to compare the integrated signal with a second reference value;
• an output unit configured to output an indication of after-pulse detection in response to the first comparison unit determining that the amplitude of the signal is greater than the first reference value and the second comparison unit determining that the integrated signal is less than the second reference value.