Circular Fringe Projection Method for 3D Profiling of High Dynamic Range Objects

Fringe projection profilometry is a widely used active optical method for 3D profiling of real-world objects. Linear fringes with sinusoidal intensity variations along the lateral direction are the most commonly used structured pattern in fringe projection profilometry. The structured pattern, when projected onto the object of interest gets deformed in terms of phase modulation by the object height profile. The deformed fringes are demodulated using methods like Fourier transform profilometry for obtaining the wrapped phase information, and the unwrapped phase provides the 3D profile of the object. One of the key challenges with the conventional linear fringe Fourier transform profilometry (LFFTP) is that the dynamic range of the object height that can be measured with them is very limited. In this paper we propose a novel circular fringe Fourier transform profilometry (CFFTP) method that uses circular fringes with sinusoidal intensity variations along the radial direction as the structured pattern. A new Fourier transform-based algorithm for circular fringes is also proposed for obtaining the height information from the deformed fringes. We demonstrate that, compared to the conventional LFFTP, the proposed CFFTP based structure assessment enables 3D profiling even at low carrier frequencies, and at relatively much higher dynamic ranges. The reasons for increased dynamic range with circular fringes stem from the non-uniform sampling and narrow band spectrum properties of CFFTP. Simulation results demonstrating the superiority of CFFTP over LFFTP are also presented.