Research On High-accuracy 3D Measurement Method Of The Larger Complex Object

The 3D measurement method is the one of the key basic method in modern manufacturing, which is a high technology combining light, electricity, machinery,computer technology into an organic whole. It also provide the necessary 3D data for product manufacturing, which is of great significance in modern nondestructive tests.Fringe projection profilometry has the advantages of non-contact operation, full-field acquisition, and easy information processing,which is of great potentiality of development in structured light 3D measurement method. It has important scientific significance and broad application foreground in the research of larger complex objects with high-precision three-dimensional measurement based on the fringe projection profilometry, which makes it possible to directly measure 3D profile of the medium and large complex objects. It also can provide data support for the digital manufacture of the medium and large complex objects, reverse engineering and virtual manufacturing.The traditional fringe projection profilometry mostly adopt the intersecting axis measurement system, but this measurement system will bring about some problem when measuring larger complex objects by this intersecting axis measurement system. First, the grating fringe on the reference plane is broadened in the intersecting axis system because of oblique-angle projection, the measuring error caused by fringe cycle broadening becomes bigger as the object to be tested becomes larger. Second, 3D measurement of the larger complex objects needs the larger measuring range, the larger measuring range will induce the bigger lens distortion of the CCD camera, which will reduce the measurement accuracy. Therefore, the problems of the fringe cycle broadening and the lens distortion need to be further studied.Firstly, in order to solve fringe cycle broadening, the theoretical model of the temporal phase unwrapping method based on the fringe cycle correction is studied in this paper. This paper establishes the mapping model between projection plane and reference plane, this model generates the uniform sinusoidal fringe on the reference plane by producing the nonuniform sinusoidal fringe on the projection plane and can realize fringe cycle correction. These sinusoidal fringes which has fringe cycle correction function can incorporate into the temporal phase unwrapping method, then obtaining the temporal phase unwrapping method based on fringe cycle correction, this method can obtain high-accuracy 3D measurement of larger complex objects.Secondly, this paper sets up lens distortion correction model based on newton iteration method to achieve lens distortion correction. This paper achieves lens distortion correction by using newton iteration method and lens distortion correction model on the basis of camera calibration, correction’s effect is fine, the measurement accuracy of the proposed method is significantly improved.The experiment results in this paper show that: The temporal phase unwrapping method based on the fringe cycle correction proposed by this paper can effectively correct fringe cycle broadening and improve measurement accuracy. Lens distortion correction model based on newton iteration method can effectively correct lens distortion of the CCD camera, which can achieve the high-accuracy 3D measurement of larger complex objects.