Device for measuring the thickness of layers with a radionuclide irradiating the layer

Claim 1

Device for measuring the thickness of layers comprising radionuclide means irradiating the layer, which radionuclide means produces energy proportional to the thickness of the layer, detector means which receives the backscatter radiation backscattered from the layer and a possibly present carrier material and produces at its output end a pulse rate, X, in the region between a lower first count, corresponding to the backscatter belonging to layer thickness zero, Xo, and an upper count belonging to the region of a quasi-infinitely thick layer, Xs, series connected indicator means, and controllable digital computing means between the detector means and the indicator means for allowing for the non-linear relationship between count rate and layer thickness, said digital computing means comprising: means for inputing a dimensionless constant, a, associated with the radionUclide being used and the particular combination of layer and carrier materials being measured, means for input a length-effected, one dimensional, constant, c, associated with the radionuclide being used and the particular combination of layer and carrier materials being measured, means for normalizing the output count from said detector means comprising means for dividing the difference between said detected count and said lower first count corresponding to layer thickness zero by the difference between said upper count corresponding to a quasi-infinitely thick layer and said lower first count, and means for linearizing said normalized count, Xhd n, in accordance with the following function, in which Y is the thickness of the layer to be measured: