Fig. 1. Design space of QIS

Fig. 2. Response curves under different bit-depths

Fig. 3. Influence of different sampling depth on dynamic range

Fig. 4. QIS imaging model

Fig. 5. PDF curve when k is 0 and 1

Fig. 6. EBR varing with read noise

Fig. 7. Photon counting error varing with read noise

Fig. 8. Photon counting error varing with λ

Fig. 9. Dynamic range and offset metric under different bit-depths

Fig. 10. ADC structure with gain stages

Fig. 11. Schematic diagram of 3-bit ADC circuit

Fig. 12. Working sequence diagram of 3-bit ADC

Fig. 13. Offset simulation results of ADC

Fig. 14. Power consumption of ADC

Fig. 15. Comparison of power consumption between traditional flash ADC and improved ADC