Analog to digital conversion technique for spectroscopy

An analog to digital conversion technique for spectroscopy enables the use of detectors in which resolution varies as a function of energy, and analog to digital converters with relatively poor differential linearity without sacrificing the ability to determine the locations and magnitude of peaks within a spectrum. A transfer function that characterizes the dependence of the resolution of the system is used to convert data before the data is displayed in a histogram. The transfer function can also characterize repeatable non-linearities in the system. The invention is particularly useful for gamma ray spectroscopy with sodium iodide detectors. The transform function can be implemented in a digital circuit, an analog circuit, or in a firmware or software transform table.