System and method of fluorescence polarimetry
First Claim
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1. A fluorescene polarimeter comprising:
- an illumination source providing a defined, narrow band light beam;
a sample cell for containing a sample solution and disposed to receive light from said illumination source and to permit fluorescent radiation from a sample solution;
an analyzer;
means for providing continuous rotation of said analyzer;
an optical filter receiving fluorescent radiation from said sample cell and having a pass band centered at the emission frequency of said fluorescent radiation;
photodetector means operative in response to radiation passed by said optical filter to provide an electrical output signal representative of radiation intensity;
signal processor means operative in response to the output signal from said photodetector means and including;
means for providing first and second signals respectively representative of the difference component and the sum component of fluorescence polarization;
means providing a time interval representing the ratio of said first signal to said second signal and including;
first integrator means receiving said second signal and providing a first integrated output signal;
second integrator means receiving a signal derived from said first signal and providing a second integrated output signal of maximum level determined by the maximum level of said first integrated output signal; and
means causing the discharge of said second integrator means at a uniform rate to provide said time interval; and
means operative in response to said time interval to provide a signal representative of polarization of fluorescence.
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Abstract
A system and method for measurement of the polarization of fluorescence. A laser source provides a collimated linearly polarized beam of high intensity and small cross-section. A relatively small number of optical components are employed to minimize spurious fluorescence and spurious polarization which usually occurs from most optical materials. A photodetector provides an electrical signal in response to and representative of fluorescence polarization and is processed to directly produce first and second signals representing the difference and sum components of the polarization equation, the ratio of these components being directly provided without need for division computation.
54 Citations
39 Claims
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1. A fluorescene polarimeter comprising:
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an illumination source providing a defined, narrow band light beam; a sample cell for containing a sample solution and disposed to receive light from said illumination source and to permit fluorescent radiation from a sample solution; an analyzer; means for providing continuous rotation of said analyzer; an optical filter receiving fluorescent radiation from said sample cell and having a pass band centered at the emission frequency of said fluorescent radiation; photodetector means operative in response to radiation passed by said optical filter to provide an electrical output signal representative of radiation intensity; signal processor means operative in response to the output signal from said photodetector means and including; means for providing first and second signals respectively representative of the difference component and the sum component of fluorescence polarization; means providing a time interval representing the ratio of said first signal to said second signal and including; first integrator means receiving said second signal and providing a first integrated output signal; second integrator means receiving a signal derived from said first signal and providing a second integrated output signal of maximum level determined by the maximum level of said first integrated output signal; and means causing the discharge of said second integrator means at a uniform rate to provide said time interval; and means operative in response to said time interval to provide a signal representative of polarization of fluorescence. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 28)
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15. A fluorescence polarimeter comprising:
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an illumination source providing a defined, narrow band light beam; a sample cell for containing a sample solution and disposed to receive light from said illumination source and to permit fluorescent radiation from a sample solution; an analyzer; means for providing continuous rotation of said analyzer; an optical filter receiving fluorescent radiation from said sample cell and having a pass band centered at the emission frequency of said fluorescent radiation; photodetector means operative in response to radiation passed by said optical filter to provide an electrical output signal representative of radiation intensity; signal processor means operative in response to the output signal from said photodetector means and including; bandpass filter means providing a first signal directly representative of the difference component of fluorescence polarization; lowpass filter means providing a second signal directly representative of the sum component of fluorescence polarization; amplifier means coupled to said bandpass filter means and providing an amplified version of said first signal; a phase sensitive detector receiving said amplified first signal and providing an output signal; first integrator means operative in response to said second signal to provide a first integrated output signal second integrator means operative in response to said output signal to provide a second integrated output signal; first comparator means providing a first comparator output signal when said first integrated output signal exceeds a reference threshold; second comparator means providing a second comparator output signal when said second integrated output signal exceeds a reference threshold; means operative in response to said first comparator output signal to enable operation of said phase sensitive detector and operative in response to said second comparator output signal to disable operation of said phase sensitive detector; counter means enabled in response to said first comparator output signal and disabled in response to said second comparator output signal; means operative in response to said first comparator output signal to cause controlled discharge of said second integrator means to provide a time interval representing the ratio of said first signal to said second signal; and means operative in response to said time interval to provide a signal representative of polarization of fluorescence. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27)
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29. The fluorescence polarimeter comprising:
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an excitation path having only a laser source providing a collimated, monochromatic, linearly polarized light beam of small cross section and high intensity; and a first optical filter receiving said light beam and having a pass band centered about the fundamental frequency of said laser source and operative to exclude light above and below an intended band; a sample cell for containing a sample solution and disposed to receive light from said optical filter and to permit fluorescent radiation from a sample solution; a linear polarizer disposed to receive fluorescent radiation emitted from a sample in said sample cell; means for continuously rotating said linear polarizer; a second optical filter receiving light from said rotating linear polarizer and having a pass band centered at the emission frequency of said fluorescent radiation; photodetector means operative in response to radiation passed by said second optical filter to provide an electrical output signal representative of radiation intensity; and signal processor means operative in response to said output signal to provide a signal representative of polarization of fluoresence; and wherein said polarizer rotating means includes; an air bearing having a housing and a hollow rotor disposed therein for rotation about an axis coincident with the axis of received fluorescent radiation; said linear polarizer being mounted on said rotor symmetrical about said axis for rotation with said rotor; pneumatic means providing an air layer between the confronting surfaces of said housing and said rotor; and pneumatic means for directing a jet of air onto a surface of said rotor to cause rotation thereof. - View Dependent Claims (30, 31)
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32. For use in a fluorescence polarimeter having an illumination source for exciting a sample solution, a continuously rotating analyzer, and a photodetector providing an output signal in response to fluorescent radiation received from the sample solution, a signal processor comprising:
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means for providing first and second signals respectively representative of the difference component and the sum component of fluorescence polarization; means providing a time interval representing a ratio of said first signal to said second signal and including; first integrator means receiving said second signal and providing a first integrated output signal; second integrator means receiving a signal derived from said first signal and providing a second integrated output signal of maximum level determined by the maximum level of said first integrated output signal; and means causing the discharge of said second integrator means at a uniform rate to provide said time interval; and means operative in response to said time interval to provide a signal representative of polarization of fluorescence. - View Dependent Claims (33)
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34. A fluoresence polarimeter comprising:
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an excitation path having only a laser source providing a collimated, monochromatic, linearly polarized light beam of small cross section and high intensity; and a first optical filter receiving said light beam and having a pass band centered about the fundamental frequency of said laser source and operative to exclude light above and below an intended band; a sample cell for containing a sample solution and disposed to receive light from said optical filter and to permit fluorescent radiation from a sample solution; an analyzer; means for continuously rotating said analyzer; a second optical filter receiving light from said rotating linear polarizer and having a pass band centered at the emission frequency of said fluorescent radiation; photodetector means operative in response to radiation passed by said second optical filter to provide an electrical output signal representative of radiation intensity; and signal processor means operative in response to said output signal to provide a signal representative of polarization of fluorescence; and wherein said rotating means includes; a hollow rotor disposed within a housing for rotation therein about an axis coincident with the axis of received fluorescent radiation; said analyzer being mounted on said rotor symmetrical about said axis for rotation with said rotor; means for providing rotation of said rotor about said axis; a plurality of sensible elements disposed about the periphery of said rotor; and control signal providing means including a transducer operative upon detection of said sensible elements to provide control pulses representative of the position and speed of said rotor. - View Dependent Claims (35)
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36. A fluorescence polarimeter comprising:
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an illumination source providing a defined, narrow band light beam; a sample cell for containing a sample solution and disposed to receive light from said illumination source and to permit fluorescent radiation from a sample solution; an analyzer; means for providing continuous rotation of said analyzer; an optical filter receiving fluorescent radiation from said sample cell and having a pass band centered at the emission frequency of said fluorescent radiation; photodetector means operative in response to radiation passed by said optical filter to provide an electrical output signal representative of radiation intensity; signal processor means operative in response to the output signal from said photodetector means and including; means for providing first and second signals respectively representative of the difference component and the sum component of fluorescence polarization; means providing a time interval representing the ratio of said first signal to said second signal and including; first integrator means providing a first integrated output signal in response to said second signal; second integrator means providing a second integrated output signal in response to a signal derived from said first signal; said second integrator means being operative for an integration time determined by the integration time of said first integrator means to cause a second integrated output signal of maximum level determined by the maximum level of said first integrated output signal; and means causing the discharge of said second integrator means at a uniform rate to provide said time interval which represents the ratio of said difference component to said sum component and thus the polarization of fluorescence; and means operative in response to said time interval to provide a signal representative of polarization of fluorescence.
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37. For use in a fluorescence polarimeter having an illumination source for exciting a sample solution, a continuously rotating analyzer, and a photodetector providing an output signal in response to fluorescent radiation received from the sample solution, a signal processing method comprising the steps of:
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deriving a first signal from said photodetector signal directly representing the difference component of fluorescence polarization; deriving a second signal from said photodetector signal directly representing the sum component of fluorescence polarization; integrating a signal derived from said first signal to a level determined by the level of a signal derived from said second signal; causing controlled discharge of said integrated signal to provide a time interval representing the ratio of said first signal to said second signal; and providing in response to said time interval a signal representative of polarization of fluorescence.
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38. A fluorescence polarimeter comprising:
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a laser source providing a collimated, monochromatic, linearly polarized light beam of small cross section and high intensity; a first optical filter receiving said light beam and having a pass band centered about the fundamental frequency of said laser source and operative to exclude light above and below an intended band; a sample cell for containing a sample solution and disposed to receive light from said optical filter and to permit fluorescent radiation from a sample solution; an analyzer; means for continuously rotating said analyzer; a second optical filter receiving light from said rotating linear polarizer and having a pass band centered at the emission frequency of said fluorescent radiation; photodetector means operative in response to radiation passed by said second optical filter to provide an electrical output signal representative of radiation intensity; signal processor means operative in response to said output signal to provide a signal representative of polarization of fluorescence; said signal processor means including; means providing a first signal directly representative of the difference component of fluorescence polarization; means for providing a second signal directly representative of the sum component of fluorescence polarization; means operative in response to said second signal to denote the start of a time interval; means operative in response to said first signal to denote the end of said time interval; and means operative in response to said time interval to provide an output indication of polarization of fluorescence.
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39. The fluorescence polarimeter comprising:
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a laser source providing a collimated, monochromatic, linearly polarized light beam of small cross section and high intensity; a first optical filter receiving said light beam and having a pass band centered about the fundamental frequency of said laser source and operative to exclude light above and below an intended band; a sample cell for containing a sample solution and disposed to receive light from said optical filter and to permit fluorescent radiation from a sample solution; a linear polarizer disposed to receive fluorescent radiation emitted from a sample in said sample cell; means for continuously rotation said linear polarizer; a second optical filter receiving light from said rotating linear polarizer and having a pass band centered at the emission frequency of said fluorescent radiation; photodetector means operative in response to radiation passed by said second optical filter to provide an electrical output signal representative of radiation intensity; and signal processor means operative in response to said output signal to provide a signal representative of polarization of fluorescence; said signal processor means including; bandpass filter means providing a first signal directly representative of the difference component of fluorescence polarization; lowpass filter means providing a second signal directly representative of the sum component of fluorescence polarization; amplifier means coupled to said bandpass filter means and providing an amplified version of said first signal; a phase sensitive detector receiving said amplified first signal and providing an output signal; first integrator means operative in response to said second signal to provide a first integrated output signal; second integrator means operative in response to said output signal to provide a second integrated output signal; first comparator means providing a first comparator output signal when said first integrated output signal exceeds a reference threshold; means operative in response to said first comparator output signal to enable operation of said phase sensitive detector and operative in response to said second comparator output signal to disable operation of said phase sensitive detector; counter means enabled in response to said first comparator output signal and disabled in response to said second comparator output signal; means operative in response to said first comparator output signal to cause controlled discharge of said second integrator means; wherein said polarizer rotating means includes; an air bearing having a housing and a hollow rotor disposed therein for rotation about an axis coincident with the axis of received fluorescent radiation; said linear polarizer being mounted on said rotor symmetrical about said axis for rotation with said rotor; pneumatic means providing an air layer between the confronting surfaces of said housing and said rotor; pneumatic means for directing a jet of air onto a surface of said rotor to cause rotation thereof; sensor means disposed in operative association with said rotor; a plurality of magnetic slugs disposed about a periphery of said rotor for sensing by said sensor means; said sensor means providing control signals representative of the position and speed of rotation of said rotor; and said signal processor means including means controlled by said control signals.
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Specification