1. A method for operating a machine vision inspection system to determine a fluorescent imaging height for acquiring a fluorescent image for repeatably determining the location of a workpiece feature edge that is located within a layer of fluorescent material on a workpiece, the method comprising: (a) positioning an exposed portion of a surface of the workpiece such that its height may be determined by the machine vision inspection system, wherein the exposed portion is not covered by the layer of fluorescent material and has a characteristic surface height along a focus axis relative to a height within the layer of fluorescent material; (b) configuring the machine vision inspection system to determine the height of the exposed portion; (c) determining the height of the exposed portion; (d) determining a fluorescent imaging height to be used for fluorescent imaging of the workpiece feature edge that is located within the layer of fluorescent material, wherein the fluorescent imaging height is determined in relation to the determined height of the exposed portion; and performing at least one of (e) and (f), wherein (e) comprises: (e) storing the determined fluorescent imaging height in association with a part program for later use when acquiring a fluorescent image that is used for inspecting the workpiece feature edge that is located within the layer of fluorescent material, and (f) comprises: (f) using the fluorescent imaging height determined in relation to the determined height of the exposed portion during execution of a part program when acquiring a fluorescent image that is used for inspecting the workpiece feature edge that is located within the layer of fluorescent material.