Projected fringes for the measurement of large aluminum ingots

Abstract

The method of projected fringes is applied to the measurement of the surface topography of aluminum ingots with surface areas of several square meters. The measurements are performed inside the casting hall of an aluminum factory. To meet the challenges encountered in such a demanding environment, it is important to keep the equipment as simple and robust as possible. Therefore a method for locating the fringe positions with sub-pixel accuracy without using for example phase shifting techniques is applied. Also the nonlinearity of the phase when using divergent illumination is discussed. The developed measuring system is tested measuring eight different aluminum ingots, and the results agree very well compared to a standard manual measurement method.

Online dimensional control of rolled steel profiles using projected fringes

“…Projected fringes are a full-field method for mapping the topography of surfaces [1][2][3][4][5][6][7][8][9][10][11][12][13]. It consists of imaging the fringes projected onto the surface with subsequent processing of the fringe data.…”

Deformation measurement of circular steel plates using projected fringes

“…In recent years, it has been combined with phase shift techniques [6][7][8][9][10][11][12] or Fourier transform methods [13][14][15][16][17][18]. With some exceptions [19,20], reports from work with these methods are done inside the optical laboratory. Recently, the authors in [21] have developed an optical measurement system to measure surface profile and three-dimensional deformation of small objects simultaneously, by a combination of fringe projection and a two-dimensional digital image correlation technique.…”

Accurate phase expansion on reference planes in grating projection profilometry

“…In fringe projection profilometry [1][2][3], the method based on phase shifting profilometry (PSP) [4][5][6] can obtain the measured object's 3D profile from the unwrapped phase of every pixel in the measured object. The unwrapped phase is obtained by projecting a sine fringe to the measured object, grabbing the modulated fringe images of the measured object, processing the grabbed images to get the wrapped phase, and demodulating the wrapped phase using temporal phase unwrapping algorithms [7][8][9][10].…”