Driving Structured-Illumination Microscopy towards the Limits of Efficiency and Accuracy

Structured-illumination microscopy (SIM) is an incoherent and simple method to measure technical surfaces with a height (z-) uncertainty down to a few nanometers. It can measure rough and smooth objects with steep slopes (<80°). Thus, it is the proper tool to inspect wafers, micro optical components, micro cutting tools, etc. One advantage of SIM over white-light interferometry and confocal microscopy is that the z-sensitivity of the system can easily be scaled by the period of the projected fringes. Besides the fringe period there is another parameter, the sampling distance of the z-scan, that directly affects the resulting height uncertainty---and the measuring time (!). We investigate how these two parameters have to be chosen for a desired height uncertainty to drive the sensor as information-efficiently as possible. We will further discuss a new method that enables a continuous scanning of the object without stop-and-go. All these ideas may help to pave the way for a fast, accurate and easy to use sensor.