Abstract: The present invention is directed to systems and methods which utilize a cavity ringdown spectroscopy (CRDS) technique for measuring vapor transmission rate through a barrier film by first allowing the vapor to accumulate over a period of time after a steady state condition has been achieved. In this manner, in one embodiment, water permeation through a plastic film, even at very low permeability rates, can be accumulated over time. The accumulated water vapor is then measured and a calculation made as to permeation per unit of time. One main advantage of the accumulated method is that minimum vapor detection is limited only by the ability to produce a good seal around the edges of the plastic film in the sample cell.

Abstract: The present invention is directed to systems and methods which utilize a cavity ring-down spectroscopy (CRDS) technique implemented for the measurements of vapor transmission rate. In one embodiment, the vapor content to be measured is contained within an optical cavity. Light is then injected into the cavity up to a threshold level and the delay time of the injected light is measured. When the wavelength of the injected light is resonant with an absorption feature of the vapor the decay time increases linearly as a function of vapor content. In this manner, vapor content causes a longer delay time and thus the amount of vapor passing through the film (film permeation rate) can be determined in real-time.