Dual self-image technique for beam collimation. (14th June 2016)

• Record Type: Journal Article
• Authors: Herrera-Fernandez, Jose Maria; Sanchez-Brea, Luis Miguel; Torcal-Milla, Francisco Jose; Morlanes, Tomas; Bernabeu, Eusebio
• Is Part Of: Journal of optics. Volume 18:Number 7(2016:Jul.)
• Publication Date: 2016-06-14
• Subjects: Talbot effect -- self-imaging -- collimation -- diffraction; Optics -- Periodicals; 535.05
• DOI: 10.1088/2040-8978/18/7/075608
• Languages: English
• ISSNs: 2040-8978

Abstract

Abstract: 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 δ ϕ = ± 1.57 μ rad .