Research On Adaptive Three-dimensional Measurement Method And Reconstruction Using Multi-line Structured Light

With the development of industrial production, there are more and more work ofthe production mould for complex workpiece surface, and it has higher requirementsfor its precision. Multi-line structured light is known for its high response and highresolution. It was rapidly developed with the promotion of high performance devices,and it has been widely used in the area of industrial, medical, mould design,manufacturing and testing and so on, especially in the ‘reverse engineering’. Butwhen the multiple linear stripes of same pitch was used in the big distribution surfaceand the system required its precision, the projected stripes would be crowded andeven would not distinguish after modulation, and finally it led to the decoding error.For this problem, this paper made the following work:Firstly, this paper analyses the composition of three dimensional system usingmulti-line structured light and the measurement principle of phase shift method, andelaborately expounds the projector calibration method using projection center in thesystem calibration.Secondly, this paper improves the linear exponential unfolding algorithm on thebasis of the classic phase unfolding algorithm. Usually the phase shift method needsat least12images to unfold the phase, this improved method can only need8imagesto unfold the phase. This method needs less images, its unfolding speed is fast, and itcan achieve the similar accuracy.Thirdly, this paper adjusts the stripes pitch of the corresponding pattern in theprojection pattern by analyzing the phase gradient of the fixed pitch stripes whichcan not decode, the corresponding area which can decode should remain the same,then obtains the adaptive projection pattern of local changing pitch. This paper uses the single measurement of adaptive projection pattern to acquire the accurate threedimensional information of the surface, and it avoids the problems of multiplemeasurement using the fixed pitch stripes, the large amount of data and additionalerror and so on. In order to make the adaptive pattern measuring accurately, thispaper uses the interpolation calculation method to reconstruct a new reference plane.Then, according to the geometric complexity of the measured object, we use thethree dimensional data to reconstruct the measured target using the three dimensionalreconstruction algorithm based on adaptive center selection.Finally, we construct the simulation measurement system of the structured light,measure and reconstruct the step plane and connected body module separately. Thesimulation results show that this paper has some advantages in improving theaccuracy of decoding using the adaptive projection pattern to measure the surface ofbig distribution normal vector only once.