Homogenization of on-axis intensity distribution produced by a Fresnel refractive axicon |
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Authors: | Brahim Chebbi Ilya Golub Kevin Gourley |
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Institution: | 1. Echo lab, Department of Ultrasound Imaging, Renmin Hospital of Wuhan University, Wuhan 430060, China;2. Department of Ultrasound Imaging, Xinqiao Hospital, Third Military Medical University, Chongqing 400037, China;3. Department of Pediatrics, Renmin Hospital of Wuhan University, Wuhan 430060, China |
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Abstract: | The on-axis intensity distribution of a beam generated by a Fresnel axicon (fraxicon) is experimentally and numerically examined and compared to a classical axicon. Monochromatic illumination produces strong oscillations in this distribution due to diffraction from the fraxicon facets combined with shadowing effects. It is shown that by proper selection of the ratio of the illuminating light wavelength to the period of the fraxicon these oscillations can be minimized by exploiting interference. In addition, polychromatic illumination of the fraxicon also permits homogenization of the on-axis intensity with some remaining oscillations at the start of the depth of field which can be reduced by decreasing the period of the fraxicon. |
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