{"content":[{"text":"Large Field of View, High Spatial Resolution, Surface Measurements \n James C. Wyant and Joanna Schmit \n WYKO Corporation, 2650 E. Elvira Road \n Tucson, Arizona 85706, USA \n jcwyant@wyko.com and jschmit@wyko.com \n www.wyko.com \n & \n Optical Sciences Center \n University of Arizona \n Tucson, Arizona 85721, USA \n www.opt-sci.arizona.edu","bbox":{"left":0.161716,"top":0.110319,"width":0.676007,"height":0.19000500000000003}},{"text":"SUMMARY \n It is difficult in interferometric metrology to maintain high spatial resolution over a large field of \n view. Interferometric microscope measurements yield high resolution, but only over a small \n area. Other conventional interferometric systems can measure large areas, but they fail to \n provide the necessary spatial resolution. High spatial resolution over a large field-of-view (FOV) \n can be obtained by stitching together multiple high spatial resolution measurements of adjacent \n areas of a measured surface. The measurements can be fit together in a global sense, or by \n matching the piston and tilt over the overlap region. Care must be taken in the stitching process \n to make sure the measurements are precisely overlapped to minimize errors. The larger the \n overlap the easier it is to match data sets, but of course more data sets are required to get a given \n field of view. This paper shows that a 20 percent overlap gives a good trade off between having \n good repeatability and obtaining a large field of view with a minimum number of data sets. \n Typical measurement results are shown for stitching as many as 285 sub-regions.","bbox":{"left":0.147206,"top":0.327311,"width":0.708509,"height":0.200287}},{"text":"1.","bbox":{"left":0.147206,"top":0.554585,"width":0.013529000000000013,"height":0.019306000000000045}},{"text":"INTRODUCTION","bbox":{"left":0.17661,"top":0.554585,"width":0.14393499999999998,"height":0.019306000000000045}},{"text":"Interferometric optical microscopic profilers \n are often used for the measurement of \n surface microstructure (1-3). Two modes of \n operation are generally available for the \n optical profilers. For smooth surfaces the \n phase-shifting integrating bucket technique \n is generally used since it gives sub- \n nanometer height resolution capability (4-5). \n For rougher surfaces, a vertical scanning \n coherence sensing technique can be used to \n give nanometer height resolution over \n several hundred microns of surface height \n (6-9).","bbox":{"left":0.147206,"top":0.584754,"width":0.32458000000000004,"height":0.20042000000000004}},{"text":"microns and the FOV is 4.9 x 3.2 mm. For a \n 50X magnification, the spatial sampling is \n 0.2 microns and the FOV is 0.15 x 0.10 mm. \n One approach for increasing the FOV, while \n keeping the spatial sampling constant, is to \n use a larger detector array, however this \n gives only a factor of about 2 increased \n field. Another approach, which can give a \n much larger field of view, is to stitch \n together several smaller FOV measurements \n to obtain a larger FOV high spatial \n resolution image. While the stitching \n approach is not new, the availability of \n precision stages with high-accuracy optical \n encoders, and fast micro-computers having \n lots of memory makes the stitching \n approach much more attractive at the \n present time than it was a few years ago. \n However, there are still many sources of \n error that must be considered before one can \n obtain high resolution, large field-of-view \n images.","bbox":{"left":0.529565,"top":0.554463,"width":0.32438200000000006,"height":0.33679000000000003}},{"text":"In order to obtain sufficiently high spatial \n sampling the FOV is typically very small. \n As an example, for a commonly used 740 x \n 480 element detector array and a 1.5X \n magnification between the sample and the \n detector array, the spatial sampling is 6.6","bbox":{"left":0.147206,"top":0.796883,"width":0.32384,"height":0.094356}}],"images_bbox":[],"images_bbox_not_text_overlap":[]}