Three-dimensional measurement of object surfaces with complex shape and color distribution based on projection of color fringe patterns

Abstract

A challenging issue associated with three-dimensional (3D) fringe patterns profilometry (FPP) is the unwrapping of phase maps resulting from color object surfaces. This paper proposes a new colorprojectionbased 3D FPP, making use of the three primary color channels [i.e., red, green, and blue (RGB)] associated with digital projectors. One channel (e.g., red) is used for projecting sinusoidal fringes required by phase shift profilometry (PSP); the other two channels are employed for generating binary stripe patterns. In order to achieve reliable phase unwrapping, each fringe of the sinusoidal patterns is identified by a unique binary sequence. These sequences are then encoded by a channel-encoding scheme used in the area of communication. The encoded sequences are embedded in the binary coding stripe images, which are projected together with the sinusoidal patterns. The three image patterns are reflected by the object surface and captured by an RGB 3-CCD camera. The reflected sinusoidal patterns are employed to yield a wrapped phase map, and the binary stripe patterns are used to retrieve the encoded sequences, which are then decoded to yield the original binary sequences for phase unwrapping. Compared with existing color-encoded algorithms, the proposed approach uses binary codes instead of fringe color to identify the fringes, which are less sensitive to the disturbances caused by object surface color and illumination noises. Furthermore, use of the channel-coding scheme provides extra resistance to the disturbances caused by object surface color and illumination noises. Experimental results are presented to confirm the effectiveness of the proposed technique. A challenging issue associated with three-dimensional (3D) fringe patterns profilometry (FPP) is the unwrapping of phase maps resulting from color object surfaces. This paper proposes a new colorprojection-based 3D FPP, making use of the three primary color channels [i.e., red, green, and blue (RGB)] associated with digital projectors. One channel (e.g., red) is used for projecting sinusoidal fringes required by phase shift profilometry (PSP); the other two channels are employed for generating binary stripe patterns. In order to achieve reliable phase unwrapping, each fringe of the sinusoidal patterns is identified by a unique binary sequence. These sequences are then encoded by a channel-encoding scheme used in the area of communication. The encoded sequences are embedded in the binary coding stripe images, which are projected together with the sinusoidal patterns. The three image patterns are reflected by the object surface and captured by an RGB 3-CCD camera. The reflected sinusoidal patterns are employed to yield a wrapped phase map, and the binary stripe patterns are used to retrieve the encoded sequences, which are then decoded to yield the original binary sequences for phase unwrapping. Compared with existing color-encoded algorithms, the proposed approach uses binary codes instead of fringe color to identify the fringes, which are less se...

Phase unwrapping method based on multiple fringe patterns without use of equivalent wavelengths

“…We still assume that there are W pixels in the direction vertical to the fringe strips, and three fringe patterns are projected with wavelengths 1 (4) is not needed. In order to achieve this, the three wavelengths are chosen to meet the following relationships: …”

“…Fringe pattern profilometry (FPP) [1] has become an effective technology for non-contact measurement of 3D shapes, which has found various applications such as manufacturing inspection, medical sciences, reverse engineering, quality control, etc.…”

Color profilometry techniques: A review

“…These techniques can be generated using a combination of binary fringes, color-coded discrete fringes, sinusoidal patterns, and phase-shifting [30][31][32][33][34][35][36][37][38][39][40]. There are different variations of hybrid phase-shifting, for either a single-shot or multi-shot method.…”

“…Hybrid phase-shifting techniques are not exclusively based on the use of a sinusoidal pattern, they can also be presented as a series of binary or discrete color fringes with a small phase-shift or stepping in-between [37][38][39][40]. The sequenced patterns can be projected either simultaneously for a single-shot method, as shown in Fig 14; or in sequence for a multi-shot capture mode, as shown in Fig.…”

Improved differential 3D shape retrieval

“…Many spatial and temporal phase retrieval methods have been presented for phase unwrapping [1][2][3]. They have made great progress in 3D surface measurement.…”