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. 2016 May 3;6:25348. doi: 10.1038/srep25348

Figure 4.

Figure 4

(a) The experimental setup used for the lens characterization. A 635 nm laser is used to illuminate the Fresnel lens, which is adjusted by two convex lenses, a filter and a diaphragm to improve collimation. A CCD camera captures the image of the focal region of the lens. By moving the camera along the z-axis, the focus intensity distribution can be detected; (b) The lens is maintained on a customized sample holder with six clamps for holding and stretching the lens in the radial direction.