Search Results (2)

Fringe projection is an important technology in three-dimensional measurement and target recognition. The measurement accuracy depends heavily on the calibration of the absolute phase and projector pixels. An easy-to-implement calibration method based on the Random Sample Consensus (RANSAC) algorithm is proposed to exterminate the phase error data and elevate the measurement accuracy in a fringe projection system. The reconstruction experiments of a double-sphere standard demonstrate that the uncertainties in radius and sphere-distance measurement are reduced to one thousandth of the measured value or even less, and the standard deviation in multiple measurements is restricted to within 50 μm. The measurement accuracy provided by the proposed RANSAC method can be improved by up to 44% compared with that provided by traditional least squared method (LSM). The proposed calibration method is easy and simple to implement, and it does not need additional hardware, but rather a calibration board. Full article

Fringe projection profilometry has been intensively studied for several decades. However, due to the limitation of the field range of a single projector, when measuring objects with complex surfaces, there are always shadow areas in the captured images, resulting in missing measurement data in the dark areas. To solve this problem, systems with double projectors and single camera were employed. Not only were the shadow areas reduced, but system recalibration and multiple measurements were not needed, improving measuring efficiency. Nevertheless, separating the corresponding projection pattern from the superimposed fringe presented a difficult problem. A color camera has RGB three color channels. When the color camera is applied to fringe projection profilometry, the information obtained is three times as much as that of the monochrome camera. Due to the small overlap between the red- and blue-light spectra response of color cameras, the channel color crosstalk can be ignored. This paper proposes a method to project red and blue fringe patterns from two projectors and utilize the characteristics of the red and blue channels of the color camera to separate the superposition grating pattern. The original patterns can be recovered integrally and easily. To explain the effectiveness of superimposed fringe separation, a simulation and experiments were carried out. Both of them showed that the superimposed fringe can be separated correctly, proving that our method is feasible. Full article