New developments in electronic reference controls for frequency domain optical sensing

M. R. Chatni; G. Li; D. M. Porterfield

doi:10.1117/12.819089

24 April 2009 New developments in electronic reference controls for frequency domain optical sensing

M. R. Chatni, G. Li, D. M. Porterfield

Proceedings Volume 7313, Smart Biomedical and Physiological Sensor Technology VI; 731307 (2009) https://doi.org/10.1117/12.819089
Event: SPIE Defense, Security, and Sensing, 2009, Orlando, Florida, United States

Abstract

The reference optical path is essential for optical systems which function on the basis of light interference. In the case of frequency domain (FD) fluorescence life-time optrodes, a reference LED is used as a standard for calculating the phase angle. The reference LED is configured so that radiation travels the same length to the detector as that of the fluorescence signal being analyzed. The phase shift, which provides details of fluorescence lifetime, is measured between these two signals - the fluorescence signal and reference LED signal, using a photodetector. We have designed, developed and implemented a FD optrode system without a reference LED. The key requirement of such a system is that phase shifts due to optics at wavelength of fluorescence and electronics have to be calibrated. In the reference-free system, the reference signal comes from the lock-in-amplifier which also drives the excitation LED. The lock-in-amplifier measures the phase shift between the excitation signal and the fluorescence emission signal from the photodetector and is locked at the frequency of modulation of the excitation signal. This insures higher signal to noise ratio and low-noise measurements. The reference-free optrode system removes some constraints on the coupling optics, which help improve the overall performance of the system. After development of electronics, and optimization of coupling optics, the system was calibrated in different oxygen concentration solutions to measure fluorescence intensity and lifetime of the oxygen sensitive dye platinum tetrakis (pentafluorophenyl) porphine (PtTFPP).

Citation Download Citation

M. R. Chatni, G. Li, and D. M. Porterfield "New developments in electronic reference controls for frequency domain optical sensing", Proc. SPIE 7313, Smart Biomedical and Physiological Sensor Technology VI, 731307 (24 April 2009); https://doi.org/10.1117/12.819089

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