%0 Journal Article
%A Herrera Fernández, José María
%A Sánchez Brea, Luis Miguel
%A Torcal Milla, Francisco José
%A Morlanes Calvo, Tomás
%A Bernabeu Martínez, Eusebio
%T Dual self-image technique for beam collimation
%D 2016
%@ 2040-8978
%U https://hdl.handle.net/20.500.14352/24622
%X We propose an accurate technique for obtaining highly collimated beams, which also allows testing the collimation degree of a beam. It is based on comparing the period of two different self-images produced by a single diffraction grating. In this way, variations in the period of the diffraction grating do not affect to the measuring procedure. Self-images are acquired by two CMOS cameras and their periods are determined by fitting the variogram function of the self-images to a cosine function with polynomial envelopes. This way, loss of accuracy caused by imperfections of the measured self-images is avoided. As usual, collimation is obtained by displacing the collimation element with respect to the source along the optical axis. When the period of both self-images coincides, collimation is achieved. With this method neither a strict control of the period of the diffraction grating nor a transverse displacement, required in other techniques, are necessary. As an example, a LED considering paraxial approximation and point source illumination is collimated resulting a resolution in the divergence of the beam of σ φ = ± μrad.
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