CMOS sensor for dual fluorescence intensity and lifetime sensing using multicycle charge modulation

This paper proposes a novel CMOS sensor chip that can realize both fast and accurate intensity and lifetime sensing for fluorescence. To enable high sensitivity, we propose parasitic insensitive multi-cycle charge modulation scheme for low-light lifetime extraction benefiting from simplicity, accuracy and compatibility with CMOS process. The designed in-pixel CTIA-based structure is able to capture the weak fluorescence-induced voltage signal by accumulating photon-generated charges in 25 discrete gated time windows within 10ms, in which each time window has 10us pulse width. A pinned photodiode on chip with 1.04pA dark current is utilized for fluorescence detection. The proposed CTIA-based circuitry can achieve 2.1mV/(nW/cm²) responsivity and 4.38nW/cm² resolution at 630nm for intensity measurement and 45ns resolution for lifetime measurement. We demonstrate functionality by measuring dissolved oxygen concentration with sensitivity of 7.5%/ppm and 6%/ppm in both intensity and lifetime domain.