Fringe projection is a versatile method for mapping the surface topography. In this paper, it is used to measure the deformation of steel plates under static penetration. Here, the surface shape changes continuously. Therefore, it is important to minimize the registration time. To achieve this, we apply a method of fringe location with subpixel accuracy that requires only a single exposure for each registration. This is in contrast to phase shifting techniques that require at least three separate exposures.

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.

Fringe projection is a versatile method for mapping the topography of surfaces. In this paper, it is used to measure the defects on the head of railroad rails while the rails are moving. Railroad rails are made by hot rolling. The quality of the finished product is generally good, but surface texture will deteriorate with increasing temperature. A method for online inspection therefore is very desirable. In the present experiment, dimensional inspection of the railroad rails was made online while moving at a speed of 1-2 m/s. Therefore, it is important to minimize the registration time. To achieve this, we apply a method of fringe location with subpixel accuracy that requires only a single exposure for each registration.

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This paper studies application of the method of projected fringes on measurement of the surface topography of double-curved propeller blades, produced in liquid metal, i.e. NiAl-bronze, with surface areas of about one square meter. The measurements are performed inside a grinding hall of a propeller 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 is developed for locating the fringe positions with sub-pixel accuracy. To avoid the need for a physical reference plane of sufficient area, a method of extrapolating the fringes projected on a small reference plane is applied. The method has been tested on a grinded propeller blade and the results agree very well compared to a standard manual measurement method