Optical apparatus for fluorescence polarization instrument

Claim 1

Optical apparatus for a fluorescence polarization analyzer wherein a fluorescent liquid sample is irradiated with excitation light and radiates an emission light from which the polarization, P, is determined in accordance with the expression: I(Z)-I(Y)/I(Z)+I(Y), where I(Z) is the measured intensity of one polarization component of the emitted light at a first polarization angle when the liquid sample is irradiated with polarized excitation light at the first polarization angle, and where I(Y) is the measured intensity of the polarization component of emitted light at the first polarization angle when the liquid sample is irradiated with polarized excitation light at a second polarization angle perpendicular with respect to said first polarization angle, said optical apparatus comprising: a sample tube for containing said liquid sample, said sample tube having a substantially circular peripheral cross-sectional configuration; a focused light source for irradiating said liquid sample with excitation light focused substantially at the center of said sample; said focussed light source comprising a relatively low wattage, low intensity tungsten halogen lamp; a narrow bandwith filter intermediate said focused light source and said sample for passing excitation light corresponding substantially to the absorption band of the fluorescent sample; a first polarizer intermediate said narrow bandwidth filter and said sample, said polarizer having a fixed plane of polarization at said first polarization angle; a field effect liquid crystal intermediate said polarizer and said sample, including means for alternately applying an electric field to said liquid crystal to alternately apply excitation light polarized at the first or second polarization angles to said liquid sample; a photomultiplier detector including an input aperture restricting the emission light viewed by said photomultiplier; baffle means adjacent the sample tube substantially preventing reflections of excitation light from entering the path of said emission light to said photomultiplier input aperture; emission light focusing lenses intermediate said sample and said photomultiplier for focusing emitted light to said photomultiplier input aperture; a second polarizer intermediate said sample and said photomultiplier having a fixed plane of polarization at said first polarization angle; and a wide bandwidth filter intermediate said sample and said photomultiplier for passing emitted light corresponding substantially to the emission band of the fluorescent sample.