Hidden grids, moiré patterns and optoelectronically measurement of distances

Hidden grids from the photocopy process are used to produce moiré patterns. The method of production of moiré patterns is extended to hidden grids generated in the optoelectronical CCD observations. An application of this moiré is proposed to measure distances

Projection Colour Moiré Technique for 3-D Surface Reconstruction

Moiré effect is an optical phenomenon that occurs in consequence of the coincidence of two periodical structures, gratings. Nowadays the moiré effect is used for contour generation of three-dimensional objects and measurements of deformation: strain analysis, linear or angular displacements and vibration analysis. Projection moiré method is a typical method for three-dimensional measurements. To find the absolute order of a fringe (z-coordinate of the object under research) one must define the difference in depth between two points by the moiré patterns. But to present day for extraction of an object´s three-dimensional information several moiré patterns and image processing methods such as Fourier-transform method, temporal phase shifting technique were needed, since from one moiré image it´s impossible to determine whether the object is concave or convex. It means that it was impossible to work with dynamic objects in real-time operation mode. Here we present colour moiré projection technique that resolves the arising problem of ambiguities in moiré patterns by application of only one moiré pattern. This method is based on application of colour rulings to gratings in projection moiré technique

Hidden grids, moiré patterns and optoelectronically measurement of distances

Hidden grids from the photocopy process are used to produce moiré patterns. The method of production of moiré patterns is extended to hidden grids generated in the optoelectronical CCD observations. An application of this moiré is proposed to measure distances.Facultad de Ciencias ExactasFacultad de Ingenierí

Hidden grids, moiré patterns and optoelectronically measurement of distances

Hidden grids from the photocopy process are used to produce moiré patterns. The method of production of moiré patterns is extended to hidden grids generated in the optoelectronical CCD observations. An application of this moiré is proposed to measure distances.Facultad de Ciencias ExactasFacultad de Ingenierí

Розроблення вільного програмного забезпечення для захисту документів на основі латентних муарових елементів

We are addressing the optical speedup of movements of layers in moiré patterns. We introduce a set of equations for computing curved patterns, where the formulas of optical speedup and moiré periods are kept in their simplest form. We consider linear movements and rotations. In the presented notation, all periods are relative to the axis of movements of layers and moiré bands

Analysis of colour moiré phenomenon in colour space

Moiré topographic technique is widely used for three-dimensional surface reconstruction. One of the main problems is determination of the absolute order of a fringe for finding the depth difference between two points in moiré patterns, i. e. convex and concave surfaces distinction. Most solutions of the problem are very complicated; also they usually require several moiré images. Application of colour-encoded gratings in projection moiré method allows solving the problem simply and quickly. The authors analyze the information that contains in colour moiré fringes and estimate its effectiveness. With this purpose device independent simulations for colour formation of one moiré fringe in colour space by different conditions were made

Dynamic 3D shape measurement based on the phase-shifting moir\'e algorithm

In order to increase the efficiency of phase retrieval,Wang proposed a high-speed moire phase retrieval method.But it is used only to measure the tiny object. In view of the limitation of Wang method,we proposed a dynamic three-dimensional (3D) measurement based on the phase-shifting moire algorithm.First, four sinusoidal fringe patterns with a pi/2 phase-shift are projected on the reference plane and acquired four deformed fringe patterns of the reference plane in advance. Then only single-shot deformed fringe pattern of the tested object is captured in measurement process.Four moire fringe patterns can be obtained by numerical multiplication between the the AC component of the object pattern and the AC components of the reference patterns respectively. The four low-frequency components corresponding to the moire fringe patterns are calculated by the complex encoding FT (Fourier transform) ,spectrum filtering and inverse FT.Thus the wrapped phase of the object can be determined in the tangent form from the four phase-shifting moire fringe patterns using the four-step phase shifting algorithm.The continuous phase distribution can be obtained by the conventional unwrapping algorithm. Finally, experiments were conducted to prove the validity and feasibility of the proposed method. The results are analyzed and compared with those of Wang method, demonstrating that our method not only can expand the measurement scope, but also can improve accuracy.Comment: 14 pages,5 figures. ams.or