The blur of the optical system can cause inevitable degradation of acquired images. In this paper we present a novel method to measure the spatially-varying blur of the camera lens. We obtained the Discrete Cosine Transform (DCT) coefficients of the blur kernels by applying DCT single-pixel imaging to all the camera pixels. The spatially-varying blur kernels are then reconstructed by applying inverse DCT to the acquired coefficients. Experimental results show that the proposed method can acquire a more accurate blur kernel compared to the traditional Gaussian kernel.
Traditional optical 3D shape measurement methods, such as light stripe triangulation, binary coding, and fringe projection, cannot acquire complete and correct 3D measurement results in the presence of interreflections. In this research, a 3D shape measurement method in the presence of interreflections based on light stripe triangulation is presented. The wrong measurement results caused by interreflections are excluded by the geometric constraints introduced by an additional camera. Each 3D point reconstructed by light stripe triangulation is projected onto the image plane of the additional camera to determine whether the 3D point is correct measurement result. Experimental results demonstrate that the proposed method can measure 3D shape in the presence of interreflections.
In the modern industrial manufacturing, how to effectively obtain the three-dimensional data of the parts profile is the key component for precision test and subsequent analysis. A light-duty design scheme for optical vision probe, which can be installed with a PH10T motorized probe head in CMM, is discussed in this paper. The optical probe can overcome several defects of the traditional measurement mode of CMM, such as poor efficiency and sparse point cloud. Therefore, the problem of 3D measurement and quality analysis for complicated parts can be solved. To splice data in different fields of view, a registration method using a new designed artifact is proposed. Experiments demonstrated the feasibility of the designed non-contact CMM integrated with optical 3D probe for precise 3D shape measurement. The measurement uncertainty of the optical probe can reach 0.012mm within the measuring volume width 200mm and the measurement uncertainty of the global 3D measurement is less than 0.03mm in 1500mm.
KEYWORDS: 3D metrology, 3D acquisition, Parallel computing, Heterodyning, Clouds, Phase measurement, Cameras, 3D image processing, 3D displays, Image acquisition
When fringe projection profilometry is applied for real-time 3D shape measurement, several problems remain to be solved such as multi-wavelength heterodyne phase unwrapping is sensitive to motion and the computation cost is high. In this paper, a real-time 3D shape measurement method with optimized multi-wavelength heterodyne phase unwrapping and GPU parallel computing is proposed. Experimental results demonstrate that the proposed method can acquire 3D shape at 40 fps. Dynamic object with discontinuities can be measured and the phase unwrapping mistakes are eliminated by smoothing the phase of beat frequency during multi-wavelength heterodyne phase unwrapping.
Autonomous aerial refueling is a significant technology that can significantly extend the endurance of unmanned aerial vehicles. A reliable method that can accurately estimate the position and attitude of the probe relative to the drogue is the key to such a capability. A drogue pose estimation method based on infrared vision sensor is introduced with the general goal of yielding an accurate and reliable drogue state estimate. First, by employing direct least squares ellipse fitting and convex hull in OpenCV, a feature point matching and interference point elimination method is proposed. In addition, considering the conditions that some infrared LEDs are damaged or occluded, a missing point estimation method based on perspective transformation and affine transformation is designed. Finally, an accurate and robust pose estimation algorithm improved by the runner-root algorithm is proposed. The feasibility of the designed visual measurement system is demonstrated by flight test, and the results indicate that our proposed method enables precise and reliable pose estimation of the probe relative to the drogue, even in some poor conditions.
In dental restoration, its important to achieve a high-accuracy digital impression. Most of the existing intraoral measurement systems can only measure the tooth from a single view. Therfore,if we are wilng to acquire the whole data of a tooth, the scans of the tooth from multi-direction ad the data stitching based on the features of the surface are needed, which increases the measurement duration and influence the measurement accuracy. In this paper, we introduce a fringe-projection based on multi-view intraoral measurement system. It can acquire 3D data of the occlusal surface, the buccal surface and the lingual surface of a tooth synchronously, by using a senor with three mirrors, which aim at the three surfaces respectively and thus expand the measuring area. The constant relationship of the three mirrors is calibrated before measurement and can help stitch the data clouds acquired through different mirrors accurately. Therefore the system can obtain the 3D data of a tooth without the need to measure it from different directions for many times. Experiments proved the availability and reliability of this miniaturized measurement system.
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