Camera calibration based on the back projection process
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Abstract:
Camera calibration plays a crucial role in 3D measurement tasks of machine vision. In typical calibration processes, camera parameters are iteratively optimized in the forward imaging process (FIP). However, the results can only guarantee the minimum of 2D projection errors on the image plane, but not the minimum of 3D reconstruction errors. In this paper, we propose a universal method for camera calibration, which uses the back projection process (BPP). In our method, a forward projection model is used to obtain initial intrinsic and extrinsic parameters with a popular planar checkerboard pattern. Then, the extracted image points are projected back into 3D space and compared with the ideal point coordinates. Finally, the estimation of the camera parameters is refined by a non-linear function minimization process. The proposed method can obtain a more accurate calibration result, which is more physically useful. Simulation and practical data are given to demonstrate the accuracy of the proposed method.A robot needs to localize an unknown object before grasping it. When the robot only has a monocular sensor, how can it get the object pose? In this work, we present a method of localizing the 6-DOF pose of a target object using a robotic arm and a hand-mounted monocular camera. The method includes an object recognition and a localization process. The recognition process uses point features on a surface of the target as a model of the object. The object localization process combines the robotic motion data and image data to calculate the 6-DOF pose of the object. This method can process objects containing textured planes. We verify the method in real tests.
Monocular vision
Monocular
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We present a variation on the Chamberlin trimetric map projection. This new projection, which we call the matrix trimetric projection, consists of a linear transformation of the squares of the distances between a given point and three control points. The formula of the forward projection is simpler than the Chamberlin projection, and admits an inverse formula which requires numerical iteration of only one parameter. We make comparisons between the two projections using a representative list of control points. The Chamberlin trimetric projection outperforms the matrix trimetric projection on measures of angle deformation and area deformation, but the opposite is true for a measure of distance deformation, and the difference between the results of the projections is small over all measures. The forward Matrix trimetric projection can be calculated in half the time of the Chamberlin trimetric projection. We conclude that the matrix trimetric projection is a viable alternative to the Chamberlin trimetric projection, especially if an inverse is required or speed is important.
Planar projection
3D projection
Graphical projection
Matrix (chemical analysis)
Projection method
Oblique projection
Projection plane
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Projection can measure not only the distance but also the angle between two decision objects. It has become one of important tools for complex decisions. This research finds that the existing projection formulae are unreasonable in real vector and interval vector settings. To solve this problem, th is paper develops two new normalized projection measures. And new projection measures are applied to group decision-making with hybrid decision information. The applicability and feasibility are shown by an experimental analysis. The results show that the projection measures improved in this paper are superior to the existing ones.
Projection method
Vector projection
Group Decision Making
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The uncertainty of roughness measurements and calibration is usually rather high. This paper gives some methods to estimate the uncertainty properly and proposes a dynamic calibration device and a special reference specimen to enable more accurate roughness measurements.
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We present an improved coaxial multiline through-reflect-line calibration method which allows to correct for errors in the description of calibration standards. Our approach is based on the multi-frequency formulation of the vector-network-analyzer calibration problem which accounts for the physical relationships between calibration standard S-parameters at different frequencies. We illustrate our approach with experimental results for the coaxial multiline through-reflect-line calibration with type-N airlines. We show that our calibration method significantly improves the measurement accuracy as compared with the classical multiline through-reflect-line calibration method.
Coaxial
Line (geometry)
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From the projection characteristics of the point line plane, we can conclude: Their projection has at least a similar or solid form (long) projection. It's easy to imagine how do the lines; planes and solids exist in fact. This text related how to make the similar or solid projection according to the projection characteristics, and how to educate the space to think the elephant ability.
Planar projection
Projection plane
Graphical projection
3D projection
Oblique projection
Line (geometry)
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Pressure reference leak calibration with compare method is simple and efficiency. To evaluate uncertainty of calibration specification for pressure reference leak with compare method,we establish math model,analyze the influence and the sensitivity of uncertainty,evaluate the uncertainty caused by the calibration apparatus and repeat measure,comparatively extendable uncertainty of calibration specification for pressure reference leak could be gained. At last,through experimentation,this paper gives a demonstration of calibration specification for pressure reference leak.
Leak Detection
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This article presents the results of accuracy verification of wafer-level calibration at high temperatures based on coplanar calibration standards. The electrical characteristics of different commercially available coplanar calibration lines were extracted and compared at different temperatures. Finally, the accuracy of lumped calibrations at variable temperatures was verified by definition of the worst-case error bounds for the measurement of passive devices and compared to the reference NIST multiline TRL.
NIST
Accuracy and precision
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This article presents the results of accuracy verification of wafer-level calibration at high temperatures based on coplanar calibration standards. The electrical characteristics of different commercially available coplanar calibration lines were extracted and compared at different temperatures. Finally, the accuracy of lumped calibrations at variable temperatures was verified by definition of the worst-case error bounds for the measurement of passive devices and compared to the reference NIST multiline TRL.
NIST
Accuracy and precision
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