A 512×512 SPAD Image Sensor with Built-In Gating for Phasor Based Real-Time siFLIM

Fluorescence imaging is a widely adopted technique in various scientific disciplines for mapping chemical and biological characteristics or molecular interactions in cells by generating high contrast images in a non-invasive way. Recently, fluorescence lifetime imaging microscopy (FLIM) has become a practical alternative to fluorescence intensity thanks to affordable pulsed laser sources and counting electronics. FLIM has several advantages over simple intensity imaging. Specifically, fluorescence lifetime is strongly dependent on the molecular environment but very little on concentration or excitation intensity [1]. In most FLIM setups, a histogram of photon arrival times is constructed and fluorescence lifetime is extracted using various fitting algorithms (Fig. 1). This process is time consuming, especially with multiexponential decays, often a bottleneck to realtime imaging.