Fig. 1. Principle of operation of ER-TDC. (a) Timing diagram; (b) typical example of measured histogram (δt>tpw)

Fig. 2. Schematic diagrams of two automatic systems designed and developed in this study for PDE spectrum measurement. (a) ER-TDC-based system; (b) traditional SDS method (i.e., counter)-based system

Fig. 3. Schematic diagram of the connections between SSC and LED array

Fig. 4. An automatic PDE spectrum measurement procedure based on ER-TDC

Fig. 5. Spectral emission characteristics of each LED in the LED array. (a) Emission spectra; (b) central wavelength and spectral width

Fig. 6. Normalized spectra of LED680L at different emission powers

Fig. 7. Temporal emission characteristics of each LED in the LED array. (a) Temporal profile; (b) pulse width

Fig. 8. Power calibration coefficients for individual LEDs in the LED array

Fig. 9. Distributions of event arrival times measured by the ER-TDC under LED680L illumination

Fig. 10. Distributions of event arrival times measured using the ER-TDC at different light pulse periods and the inset shows PDEs for the corresponding periods

Fig. 11. Mean number of detected photoelectrons μ and PDE as functions of incident photon flux

Fig. 12. Comparison of PDEs of the Si-SPAD measured using different methods. (a) PDE spectra; (b) relative combined standard uncertainties of PDEs