Spatial resolution limits of an optical profiler

Katherine Creath

doi:10.1117/12.22123

1 July 1990 Spatial resolution limits of an optical profiler

Katherine Creath

Proceedings Volume 1319, Optics in Complex Systems; (1990) https://doi.org/10.1117/12.22123
Event: 15th International Optics in Complex Systems, 1990, Garmisch, Germany

Abstract

Interferometric optical profilers have a spatial resolution which is either limited by the detector array sample spacing and element size or by the optical resolution of the system. To test the working spatial resolution of an optical profiler a sinsusoidal grating with 300 lines/mm was measured using an optical profiler at lOx 2Ox 40x and 200x with detector arrays having element-to-element spacings of 6. 8 j. tm and 40 tm. The highest magnification gave the greatest and most accurate depth for the grating for all of the detectors. At 40x as long as there were more than about 8 sample points per cycle as there were with the two smaller detector spacings the grating depth can be measured quite accurately. With fewer points the peak-to-valley height measurement of the grating is too low even though the optical resolution of the system is sufficient enough to resolve the grating. The results of this work show that for accurate representation of surface heights containing high frequency structures oversampling is desirable. Summary The spatial resolution of an interferometric optical proffler depends upon both the optical resolution of the system and the characteristics of the detector array used to sample the image. The limiting resolution wifi be the larger of the optical and detector resolution. One means of defining optical resolution is the Sparrow criterion which states that the image of two points is just

Citation Download Citation

Katherine Creath "Spatial resolution limits of an optical profiler", Proc. SPIE 1319, Optics in Complex Systems, (1 July 1990); https://doi.org/10.1117/12.22123

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