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.