Three-dimensional Measurement Method With Structured Light Projection

Three-dimensional measurement has found its applications in the fields ofindustry, virtual reality, cultural heritage protection, garment making, as well asmedical diagnostic. There are some disadvantages in the present three-dimensionalmeasurement methods. In the phase measurement profilometry, to eliminate themeasurement error from non-accurate phase shift and non-sinusoidal light field, it isnecessary to introduce a relatively higher accurate phase shift device as well asstandard sine grating. Fourier transform profilometry has higher sensitivity, but itsmeasurement range is limited under the condition that all levels of the spectrum notaliasing. Structured light coding method is influenced by the feature points in spatialneighborhood, so the identification and decoding of the coded image is more difficult,this increases measurement error, and there are also disadvantages of low resolutionproduced by the different reflectance and color of object surface.In this paper, the analysis of the existing three-dimensional measurement methodswas made. A structure light projection-based, non-contact and fast three-dimensionalsurface measurement method was proposed. The measurement principle is:(1)projecting a structure picture to the measured object surface;(2) imaging thedeformed structure picture on the object surface;(3) from the coordinate differences ofthe represent points on the images of structure pictures with and without the measuredobject, the three-dimensional coordinates of points on the measured object surfacecould be calculated;(4) the surface of the measured object can be constructed inthree-dimensional space.This paper includes the following aspects: (1) The basic principles of the proposed three-dimensional optical measurementmethod was described. The coordinates relations of points on the structure picture, themeasured object surface and imaged deformed picture were analyzed. The threedimensional coordinates of points on the measured object surface were calculated. Themeasurement principle was numerically simulated.(2) A projector-camera experimental system was setup and the experiments wereconducted. The experimental results are satisfactory and support the principle of themethod. The experimental system is simple and can measure changing object surface.