A Compact Analog Histogramming SPAD-Based CMOS Chip for Time-Resolved Fluorescence

Lock-In Pixel CMOS Image Sensor for Time-Resolved Fluorescence Readout of Lateral-Flow Assays

“…4 (f) in [18], (6) Estimated value for HIV antibody detection from Fig. 3 (c) in [19], (7) Procalcitonin, (8) Medisensor aQcare™ TRF system, (9) Calculated average intra-assay precision. (10) Mesoporous silica (mSiO 2 ) coated up-converting nanoparticle (UCNP)…”

“…Using time-resolved fluorescence (TRF) measurement techniques, latest developments showcase the highly sensitive detection of biochemical signals, capturing the nanosecond decay of fluorescent dyes within picoseconds [5]- [7]. Until now, high system costs and complexity due to lenses, mirrors, and filters, among others, as well as high-power excitation laser sources have prevented TRF from being used cost-effectively in PoC applications.…”

“…TRF systems with SPADs that do not use optical filters [7]- [9] are very well suited for the detection of low fluorescence intensities. On the other hand, these systems have a restricted optical dynamic range [9], [10].…”

Compact SPAD pixels with fast and accurate photon counting in the analog domain

“…The analog counter based on the charge transfer method achieves a count range of 8 bits, which is higher than that in Refs. [16,20]. The analog counter uses a pair of complementary transistors MP3 and MN4 as charge transfer switches and uses a delay inverter INV4 to control the conduction of the transistors, effectively preventing short-term charge leakage during circuit conversion, and realizing charge transfer to improve output linearity.…”

“…However, the large MOS integral capacitance in the analog counter limits the pixel fill factor. Later, a 160 × 120 pixel analog-counting single-photon imager for fluorescence lifetime imaging was presented [20] using a 0.35 μm standard CMOS process. A high fill factor of 21% is obtained, but the counting range is only 6-bit and the integral non-linearity deviation is also relatively large.…”