The Research Of The Key Techniques Of FLIM Image Sensor Based On SPADs

Fluorescence lifetime imaging is a widely used recognition-tool towards biological molecules in biological and medical areas.Fluorescence intensity is easily affected by the probe concentration,photo-bleaching and environmental absorptions.However,lifetime measurements are only related to the micro environment in which the fluorescent decay are more reliable.Photomultipliers based scanning systems are usually slow in frame rate.Hence Single Photon Avalanche Diode(SPAD)array detectors with TCSPC structure become a trend for their better compatibility and excellent performance in weak light detections,but the reported systems are typically data rate constrained.So this work focuses on reducing the data throughput as well as some research on key modules.This project proposes an imaging structure based on integrated pixels with time to digital converters and registers inside to implement the pre-processing of summation within each pixel to reduce the data throughput.In SPAD,a mainstream structure of SPAD is designed and analyzed in Verilog A model.In readout circuits,the attention is on the schematic and circuit design of the oscillator based Time to digital converter(TDC).A Phase-locked loop is adopted to provide TDCs with the bias voltage in the same row.The time quantization results are processed with Center of Mass Method(CMM)to estimate a lifetime map.A calibration method based on rapid lifetime determination is proposed to enlarge the solvable range of CMM.The chip design is implemented in 0.18?m SMIC CMOS process.The resolution of SPAD array is 10 × 10 and the pitch is 62?m with a fill factor of 1.3%.The data rate is as low as 0.01 Mbps which is attributed to the pre-processing of quantization result within pixel.The reduced power consumption is 192.6mW/pixel.The designed imaging frame rate is 400 fps with 34 dB.The proposed structure is promising in high-speed and highly integrated applications such as clinical diagnosis.