Inexpensive Digital Phase Fluorometer

Fluorescence-lifetime based sensing provides a more robust and reliable detection method than intensity measurements which are notoriously prone to systematic errors. Measurement of fluorescence lifetime is also an important adjunct to quantitative spectrofluorimetric measurements in direct fiber-optic sensing systems. The reason for this is that dynamic quenching effects by other species in the sample may disrupt the correlation between a fluorescence intensity measurement and the concentration of analyte. In these cases, a fluorescence lifetime measurement may provide the additional information required to account for the effect of quenching on the measurement. We propose to develop a 1 0 MHz single-frequency cross-correlation digital phase fluorometer which exploits recent technological developments for inexpensive generation of the light modulation and cross- correlation frequencies. Additionally, we propose to replace the expensive analog electronics in current use for the phase measurement with a digital filter and digital phase detection thereby achieving a dramatic reduction in cost, while improving performance and reliability. The proposed approach will convert the problem of accurate phase measurement from a demanding analog hardware problem to a software solution with off-the-sheff hardware.