We present a collimation technique based on a double grating system to locate with high accuracy an emitter in the focal plane of a lens. Talbot self-images are projected onto the second grating producing moiré interferences. By means of two photodetectors positioned just behind the second grating, it is possible to determine the optimal position of the light source for collimation by measuring the phase shift between the signals over the two photodetectors. We obtain mathematical expressions of the signal in terms of defocus. This allows us to perform an automated technique for collimation. In addition, a simple and accurate visual criterion for collimating a light source using a lens is proposed. Experimental results that corroborate the proposed technique are also presented.
© 2010 Optical Society of America
Diffraction and Gratings
Original Manuscript: March 11, 2010
Revised Manuscript: May 13, 2010
Manuscript Accepted: May 18, 2010
Published: June 8, 2010
Luis Miguel Sanchez-Brea, Francisco Jose Torcal-Milla, Francisco Javier Salgado-Remacha, Tomás Morlanes, Isidoro Jimenez-Castillo, and Eusebio Bernabeu, "Collimation method using a double grating system," Appl. Opt. 49, 3363-3368 (2010)