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The presented vision system integrates a focus tunable lens allows to perform fast autofocus and distance measurement at the same time. By deriving the best focus from the maximum position of a fitted distribution, it is not required to capture the image with the actual best focus during the autofocus sweep, resulting in high speed and robustness of the algorithm. In this work, we demonstrate that a focus tunable lens in conjunction with an autofocus algorithm can reliably measure distance to an arbitrary object in less than a second (depth from focus). The accuracy of the distance measurement is in line with the depth of field of the imaging system. No additional hardware is required apart from the imaging system comprising camera, objective lens and focus tunable lens. The fast and accurate focus and distance measurement enables and simplifies various applications ranging from robot vision to smart manufacturing control. The optics can be tailored to reach the desired precision and focus range, whereas there is generally a trade-off between the two.
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