A new approach for simple and rapid shape measurement of objects with surface discontinuities

Abstract

A new approach for unwrapping phase maps, obtained during the measurement of 3-D surfaces using sinusoidal structured light projection technique, is proposed. "Takeda's method" is used to obtain the wrapped phase map. Proposed method of unwrapping makes use of an additional image of the object captured under the illumination of a specifically designed color-coded pattern. The new approach demonstrates, for the first time, a method of producing reliable unwrapping of objects even with surface discontinuities from a single-phase map. It is shown to be significantly faster and reliable than temporal phase unwrapping procedure that uses a complete exponential sequence. For example, if a measurement with the accuracy obtained by interrogating the object with S fringes in the projected pattern is carried out with both the methods, new method requires only 2 frames as compared to (log 2 S +1) frames required by the later method.

Efficient multiple phase shift patterns for dense 3D acquisition in structured light scanning

“…One of the key issues with the SL principle is, without doubt, the necessary number of patterns to be projected. To compute a single PS map we need at least three images according to (4). In Fig.…”

“…an extension of this rather basic technique is needed. In [4] an additional color-coded pattern is projected, giving a rough estimate to be used during spatial unwrapping, at the expense of the color pattern being basically restricted to color neutral objects. Specially made hardware can be used to tackle the problem of unwrapping [5].…”

A novel phase-shifting method based on strip marker

“…A typical phase measuring profilometry system based on projected fringe [2][3][4][5] is constructed by a projector and a camera, the former projects sinusoidal fringe patterns upon the object, and the latter acquires the patterns that are deformed by the object's shape. Then the phase map is obtained from the images of the deformed fringe pattern.…”

“…Three-dimensional shape measurement is widely used in various fields of science and engineering [1][2][3][4][5][6][7]. Among the three-dimensional measurement techniques, the phase measuring profilometry based on projected fringe is notable for its system simplicity, non-contact nature, full-field measurement capacity, fast measurement speed, and low environmental vulnerability.…”

Efficient and Low-Cost 3D Structured Light System Based on a Modified Number-Theoretic Approach

“…In other words, ultimately computing only the depth coordinate with respect to one reference plane will not be satisfactory. (6) Simple image processing of the acquired patterns, ideally the only image processing used, should consist 2 EURASIP Journal on Advances in Signal Processing of addition, multiplication, comparison, and look-up table indexing. More complex image processing, such as finding edges, corners, detecting various shapes, centers of stripes, and color thresholding, should be avoided.…”