Radiant energy – Luminophor irradiation – Methods
Reexamination Certificate
1997-10-15
2001-03-27
Hannaher, Constantine (Department: 2878)
Radiant energy
Luminophor irradiation
Methods
Reexamination Certificate
active
06207961
ABSTRACT:
BACKGROUND OF THE INVENTION
Fiber-optic sensors have been extensively developed for many applications over the past two decades. Chemical sensors utilizing optical fibers may be fabricated from single or multimode fibers, and may be used for measurement of gases, ions, pH and organic chemicals.
The use of optical fiber as an extrinsic sensor (in which an optical fiber is only used as a transportation medium for light) for oxygen concentration presents a unique opportunity in environmental monitoring, biotechnology process control and aquaculture process control. When compared with Clark-type oxygen sensors, fiber-optic oxygen sensors have the advantage of fast response time, light weight, remotely operable, low maintenance and potentially low cost. However, the use of fluorescence intensity in a fiber-optic oxygen sensor is hampered by problems associated with optical fiber bending loss.
Recent progress in referencing techniques for intensity based optical fiber sensors has been reviewed by MURTAZA and SENIOR, and ratiometric technique such as dual-wavelength referencing configuration has been used to reduce the effect of fiber bending loss.
SUMMARY OF THE INVENTION
The invention uses a spectral slicing method in alleviating the bending loss in a fluorescence intensity based fiber-optic oxygen sensor.
Instead of using the same light source, one detector channel is used to detect the intensity of the light source while the other detector channel is used to detect the intensity of the fluorescent signal.
Digital-signal processing (DSP) technique was implemented to isolate the modulated excitation and fluorescent signals from ambient light. Digital-signal processing technique such as Fast Fourier Transformation (FFT) and signal averaging were implemented using low cost DSP chips to improve the signal-to-noise ratio (SNR) of very low intensity fluorescence signals using inexpensive photodetector/amplifier packages.
The invention provides a combination of a dichroic filter and implementation of a digital-signal processing technique thereby alleviating problems associated with fiber bending loss.
These and further and other objects and features of the invention are apparent in the disclosure, which includes the above and ongoing written specification, with the claims and the drawings.
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patent: 5470155 (1995-11-01), Jensen
G. Murtaza and J.M. Senior, “Referencing Strategies for Intensity Modulated Optical Fibre Sensors: a Review,” Optics and Laser Technology, vol. 25, No. 4, pp. 235-245, 1993.
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M.J.P. Leiner, “Luminescence Chemical Sensors for Biomedical Applications: Scope and Limitations,” Analytica Chimica Acta, vol. 255, pp. 209-222, 1991.
R.J. Watts and G.A. Crosby, “Spectroscopic Characterization of Complexes of Ruthenium (II) and Iridium (III) with 4,4'-Diphenyl-2,2'- bipyridine and 4,7'-Diphenyl-1,10-phenanthroline,” Journal American Chemical Society, vol. 93, pp. 3184-3188, Jun. 1971.
Churchill Russell J.
Groger Howard P.
Lo K. Peter
Luo Shufang
American Research Corporation of Virginia
Creighton Wray James
Hannaher Constantine
Narasimhan Meera P.
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