1. In a workpiece handling chamber, a method of performing on-the-fly spectrographic metrology of a workpiece, comprising: providing an optical sensor having a field of view coinciding with a path traversed by the workpiece during transfer in the workpiece handling apparatus, and obtaining a still image of the workpiece through said sensor during transfer of said workpiece along said path; channeling light reflected from respective image elements of said image through respective light channeling elements to respective locations of a spectrographic light disperser; recording spectral distributions of the respective image elements produced by said spectrographic light disperser; searching for distributions that are similar to one another and grouping the distributions into groups of mutually similar distributions; classifying the groups by the number of distributions contained in each group; selecting at least one of the largest groups and combining the distributions of that group together and providing the combined distribution as the spectral distribution of one region of the integrated circuit; and processing the combined distribution in accordance with a spectrum analysis process.