Wedge-plate shearing interferometers for collimation testing: use of a moiré technique

Abstract

Various optical arrangements of a double-wedge-plate shearing interferometer are presented for checking laser beam collimation. The use of moiré fringes is found to be advantageous for setting the shear fringes parallel to the direction of shear in order to obtain a well-collimated laser beam. The experimental procedure and various details of the interferometer are discussed. A brief summary of a few methods for collimation testing that use a wedge plate is also given. The accuracies achievable with shearing interferometers that use a parallel plate, a wedge plate of small angle, a double wedge having a large wedge angle, a wedge plate of large angle along with two flat mirrors, and a wedge plate having a large angle are compared and summarized.

Divergence of far-infrared laser beam and collimation for Galilean and Keplerian system designs

“…Many methods using interferometry [8][9][10] and optical materials [11] exist to test collimation in the visible light range, but very few are discussed to verify collimation in the far infrared.…”

Dual self-image technique for beam collimation

“…The variogram of a periodic signal is also periodic with the same period than the original signal. In addition, due to the averaging process performed in equation (6), the variogram function is much smoother than the original intensity distribution. Influence of grating defects on the visibility of the fringes has been reported by the authors in previous works [23,24].…”

“…Nevertheless, results are quite imprecise since the intensity distribution of the light beam usually changes as it propagates. More accurate beam collimation techniques based on different optical effects have been proposed such as those based on interferometry [1,2,3,4,5,6,7,8,9]. Selfimaging-based methods, also known as Talbot interferometry, use Talbot effect as a tool to create moiré fringes at the output of a double grating system where the second grating is placed at a self-image plane of the first one [10,11,12], z T = 2lp 2 /λ, where l is an integer, p is the period of the grating, and λ is the wavelength [13].…”

Lissajous figure-based single-frame collimation technique

“…A high number of techniques have been proposed and developed for testing the collimation degree of beams. Most of them are based on interferometry [1][2][3][4][5] or on self-imaging techniques [6][7][8][9]. In addition, several techniques have been proposed in the last years [10][11][12][13][14][15].…”