Moir$\acute{e}$ topography for 3-D contouring has a long history of development. It started with a shadow type as first proposed in 1970. Later projection type Moir$\acute{e}$ began to draw attention to extend the contouring depth limited by light diffraction in shadow type Moir$\acute{e}$. Whatever types of Moir$\acute{e}$ are used, it is important to have a suitable fringe analysis tool for effective extraction of 3-D information from generated Moir$\acute{e}$ fringes. In the beginning period until 1980s, spatial image processing techniques such as fringe tracking and Fourier transform were widely used. Recently, phase shifting Moir$\acute{e}$ technique has been intensively explored since it allows automatic handling of complex fringes with enhanced measuring resolution.
A phase shifting projection Moir$\acute{e}$ method particularly intended to implement the 3-D measurement in non-contact mode for natural objects such as human bodies is presented. Emphasis is that a set of line grating pairs are used in sequence, that provide different phase shifts and time-integral fringe capturing scheme at a same time. By using the technique, 3-D profiles of human bodies together with texture-mapped color data could be acquired with high resolution and at high speed for medical and apparel industry.
Color grating projection Moir$\acute{e}$ topography is proposed next, which allows phase-shifting fringe processing real time by using color gratings. Three sets of red, green, and blue (RGB) line gratings are aligned with a lateral offset of one third the pitch, so that three separate sets of color Moir$\acute{e}$ fringes of 2π /3 phase offset are simultaneously obtained to determine 3-D profiles of objects by using the three-bucket phase-shifting algorithm. This method works with only single operation of image capturing, thus it allows quasi-static and dynamic 3-D contouring. Optical components in a measurement system can produce various forms of aberrations, like spherical aberration, astigmatism, coma aberration, and chromatic aberration. In the case of phase shifting projection Moir$\acute{e}$ topography, the chromatic aberration could induce the polychromatic Moir$\acute{e}$ fringes with phase error that causes the measurement error for different color surface. To compensate the chromatic aberration error, color grating projection phase-shifting Moir$\acute{e}$ topography could be used and the depth information is defined as the phase of the color Moir$\acute{e}$ fringes. However one problem with the scheme of color Moir$\acute{e}$ fringes is its dependence upon the color of the target surface itself. To cancel the dependence of color Moir$\acute{e}$ fringes on the spectral reflectance of the target surface, multi-color Moir$\acute{e}$ fringes is constructed, which is composed of three kinds of color Moir$\acute{e}$ fringes of 2π/3 phase shifted from each other to get a new defined RGB color Moir$\acute{e}$ fringes that is insensitive to the color surface. Experimental results have shown that newly proposed color Moir$\acute{e}$ fringes is capable of realizing the high speed 3-D imaging and the accuracy improvement of phase-shifting projection Moir$\acute{e}$ topography.
