Method of determining a detection pattern signal comprising: receiving a base clock signal and an analog detector signal at a clock cycle of a clock signal, the analog detector signal being generated by a photon detection system , wherein the analog detector signal comprises one or more detector pulses of a predetermined pulse width at one or more temporal positions respectively, each detector pulse representing an optical pulse detected by the photon detection system , the one or more temporal positions being defined relative to the rising edge of the base clock signal; generating a first clock signal based on the base clock signal, the generating of the first clock signal including applying a first phase shift to the base clock signal so that the rising edge of first clock signal is at a first temporal position relative to the rising edge of the base clock signal; generating a first pulse signal based on the analog detector signal, the first pulse signal having a first pulse width that is smaller than the pulse width of the one or more detector pulses, the first pulse width being selected between 10 and 200 ps; the generating of the first pulse signal including: forming a first delayed detector signal by applying a first delay to the analog detector signal; forming a second delayed detector signal by applying a second delay to the analog detector signal and, determining the first pulse signal based on the first and second delayed detector signal; and, generating a digital detector pattern signal, the generating including determining a first digital signal based on the first pulse signal and the first clock signal, the first digital signal indicating whether the analog detector signal comprises a first detection pulse at the first temporal position as indicated by the rising edge of the first clock signal. receiving a base clock signal and an analog detector signal at a clock cycle of a clock signal, the analog detector signal being generated by a photon detection system , wherein the analog detector signal comprises one or more detector pulses of a predetermined pulse width at one or more temporal positions respectively, each detector pulse representing an optical pulse detected by the photon detection system , the one or more temporal positions being defined relative to the rising edge of the base clock signal; generating a first clock signal based on the base clock signal, the generating of the first clock signal including applying a first phase shift to the base clock signal so that the rising edge of first clock signal is at a first temporal position relative to the rising edge of the base clock signal; generating a first pulse signal based on the analog detector signal, the first pulse signal having a first pulse width that is smaller than the pulse width of the one or more detector pulses, the first pulse width being selected between 10 and 200 ps; the generating of the first pulse signal including: forming a first delayed detector signal by applying a first delay to the analog detector signal; forming a second delayed detector signal by applying a second delay to the analog detector signal and, determining the first pulse signal based on the first and second delayed detector signal; and, generating a digital detector pattern signal, the generating including determining a first digital signal based on the first pulse signal and the first clock signal, the first digital signal indicating whether the analog detector signal comprises a first detection pulse at the first temporal position as indicated by the rising edge of the first clock signal. <EOS>