Patent ID: 7749768

Claim:
A method of verifying the oxygen concentration of a sealed package comprising: providing a sealed package defining an interior and having a luminescent compound provided in the interior of the sealed package the luminescent compound having a luminescent emission that is sensitive to quenching by oxygen; exposing the luminescent compound to light having a wavelength that is absorbed by the luminescent compound so that the luminescent compound is promoted into an excited state; terminating the exposure of the luminescent compound when the luminescent compound achieves a steady state between excitation and luminescence; measuring luminescent intensity over a period of time to produce an exponential decay curve; calculating the coefficient of the decay curve to determine tau; measuring a temperature that is indicative of the temperature of the luminescent compound; determining the oxygen concentration within the sealed package using the equation: [O 2 ]=( A Ta ( T ) 2 +B Ta ( T )+ C Ta )(tau) 2 +( A Tb ( T ) 2 +B Tb ( T )+ C Tb )(tau)+( A Tc ( T ) 2 +B Tc ( T )+ C Tc ) wherein: T is the measured temperature; tau is the coefficient of the exponential decay curve; and A Ta , B Ta , C Ta , A Tb , B Tb , C Tb , A Tc , B Tc , and C Tc are previously determined coefficients for the luminescent compound that describes the luminescent intensity of the luminescent compound as a function of oxygen concentration and temperature; and comparing the measured oxygen concentration to a predetermined minimum or maximum to verify that the measured oxygen concentration is within acceptable limits.