A multiple-segment long-distance microscope for flow visualization and measurements

In this article, we present a new imaging technique for multiple-segment microscopy at long working distances. In many applications, images of small structures might have to be taken simultaneously at widely separated points. At present, this is a problem because with a single lens it is possible to either take an image of one structure with high resolution or image the area that includes all the structures onto the CCD chip of the camera but with a strongly reduced resolution of the single structure. We have used a micro-lens array in combination with an aperture array to blank out the space between widely distributed spots and to highly magnify the areas of interest onto one chip. An application of this technique to wall shear stress measurements via imaging of wall-mounted flexible micro-pillars is demonstrated.