The investigation of phenomena occuring into micro-plasmas created by laser is mainly based on images obtained from emitted X-rays or α,-particles. To get images, the pinhole camera is widely used but the collection efficiency of radiation or particles, as also the Signal-to-Noise ratio (S/N ratio) decrease as the spatial resolution is increased. To improve the S/N ratio one can use a coding-aperture imaging device, the collecting surface of which is much higher that the pinhole-one. In this study we have chosen a simple coding-aperture made of a circular slit cut in a thin foil which is opaque at the considered radiation. The slit width is δ = 6 μm ; the mean radius is R = 1 mm. The image reconstruction is obtained by numerical processing (Fourier-transform and filtering). The transverse spatial resolution 6t in the object is δ t = δ but can be improved by a factor of 2 or 3 if the edges of the circular slit are sharp. The axial spatial resolution (tomographic effect) δl is δl, = δt l1/R, with ll the code-to-object distance.
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