90 PL. Reu 0 10 20 30 40 50 60 70 80 90 0 1 2 3 4 5 6 7 8 9 10 Contrast [%] Resolution [lp/mm] No Filter 2Lambda 4Lambda 3.6 lp/mm 5.6 lp/mm 7.2 lp/mm Fig. 14.1 Modulation transfer function (MTF) of the three camera systems Fig. 14.2 Experimental setup showing three cameras observing a 100-mm FOV with three different speckle patterns as illustrated in the insert. The DIC subset size is shown overlaid on the mixed speckle pattern a close-up a 78 m speckle or 1.5-pixel diameter speckle. The third pattern was a combination of the large and small speckles into a single pattern to represent a situation where there are both aliased and non-aliased speckles, a situation that often occurs when spray painting speckle patterns. The three speckle patterns and the experimental setup are shown in Fig. 14.2. The three speckle patterns were then translated towards the cameras using a linear stage and precision micrometer to create a uniform stretch of the image in the x- andy-directions. This uniform stretch allows one to easily observe the influence of the interpolation bias error on the results and also provides a uniform displacement and strain field for analysis without the need of expensive precision translation stages.
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