The concept of smooth generic camera calibration for optical metrology

2016 ◽  
Vol 83 (1) ◽  
Author(s):  
Alexey Pak
Keyword(s):  
Calibration Procedure ◽  
Model Parameters ◽  
Digital Cameras ◽  
Camera Model ◽  
Imaging Geometry ◽  
Registration Data ◽  
Unbiased Manner ◽  
Projection Geometry ◽  
Local Symmetries ◽  
Generic Camera

AbstractModern digital cameras with sophisticated optics enable accurate shape measurements via a plethora of metrological techniques. In order to take advantage of the data delivered by high-resolution cameras, one needs a sufficiently flexible model to describe the imaging geometry and an adequate calibration procedure to determine the model parameters and estimate their uncertainties. In this report, we suggest the concept of a smooth generic camera model that has several advantages compared to the state-of-the-art: the description is resolution-independent and takes advantage of the natural smoothness of the projection geometry; the global and the local symmetries inherent to the view ray-based parametrization are regularized in an explicitly unbiased manner. The calibration procedure uses dense datasets that can be obtained with the technique of active screens and consistently accounts for the uncertainty in the registration data that can be extracted during pre-processing. The concept is illustrated with synthetic examples based on physically-accurate rendering.

A Sensitivity Analysis Based Method for Robot Calibration

1992 ◽  
Author(s):  
S. Kaizerman ◽  
B. Benhabib ◽  
R. G. Fenton ◽  
G. Zak
Keyword(s):  
Sensitivity Analysis ◽  
Kinematic Model ◽  
Calibration Procedure ◽  
Inverse Kinematic ◽  
Model Parameters ◽  
Robot Calibration ◽  
Adjoint Sensitivity ◽  
Analysis Methods ◽  
The Matrix ◽  
Direct Sensitivity

Abstract A new robot kinematic calibration procedure is presented. The parameters of the kinematic model are estimated through a relationship established between the deviations in the joint variables and the deviations in the model parameters. Thus, the new method can be classified as an inverse calibration procedure. Using suitable sensitivity analysis methods, the matrix of the partial derivatives of joint variables with respect to robot parameters is calculated without having explicit expressions of joint variables as a function of task space coordinates (closed inverse kinematic solution). This matrix provides the relationship between the changes in the joint variables and the changes in the parameter values required for the calibration. Two deterministic sensitivity analysis methods are applied, namely the Direct Sensitivity Approach and the Adjoint Sensitivity Method. The new calibration procedure was successfully tested by the simulated calibrations of a two degree of freedom revolute-joint planar manipulator.

Device Modeling of a-Si:H Alloy Solar Cells: Calibration Procedure for Determination of Model Input Parameters

1998 ◽  
Vol 507 ◽  
Author(s):  
M. Zeman ◽  
R.A.C.M.M. Van Swaaij ◽  
E. Schroten ◽  
L.L.A. Vosteen ◽  
J.W. Metselaar
Keyword(s):  
Solar Cell ◽  
Material Properties ◽  
Calibration Procedure ◽  
Model Parameters ◽  
Model Input ◽  
A Value ◽  
Input Parameters ◽  
Simulated Material ◽  
Good Agreement

ABSTRACTA calibration procedure for determining the model input parameters of standard a-Si:H layers, which comprise a single junction a-Si:H solar cell, is presented. The calibration procedure consists of: i) deposition of the separate layers, ii) measurement of the material properties, iii) fitting the model parameters to match the measured properties, iv) simulation of test devices and comparison with experimental results. The inverse modeling procedure was used to extract values of the most influential model parameters by fitting the simulated material properties to the measured ones. In case of doped layers the extracted values of the characteristic energies of exponentially decaying tail states are much higher than the values reported in literature. Using the extracted values of model parameters a good agreement between the measured and calculated characteristics of a reference solar cell was reached. The presented procedure could not solve directly an important issue concerning a value of the mobility gap in a-Si:H alloys.

scholarly journals IMAGE NETWORK GENERATION OF UNCALIBRATED UAV IMAGES WITH LOW-COST GPS DATA

2016 ◽  
Vol XLI-B3 ◽  
pp. 31-37 ◽  
Author(s):  
Shan Huang ◽  
Zuxun Zhang ◽  
Jianan He ◽  
Tao Ke
Keyword(s):  
Coordinate System ◽  
Low Cost ◽  
Reference Image ◽  
Model Parameters ◽  
Camera Model ◽  
Orientation Data ◽  
Network Generation ◽  
Free Network ◽  
Uav Images ◽  
Image Network

The use of unmanned air vehicle (UAV) images acquired by a non-metric digital camera to establish an image network is difficult in cases without accurate camera model parameters. Although an image network can be generated by continuously calculating camera model parameters during data processing as an incremental structure from motion (SfM) methods, the process is time consuming. In this study, low-cost global position system (GPS) information is employed in image network generation to decrease computational expenses. Each image is considered as reference, and its neighbor images are determined based on GPS coordinates during processing. The reference image and its neighbor images constitute an image group, which is used to generate a free network through image matching and relative orientation. Data are then transformed from the free network coordinate system of each group into the GPS coordinate system by using the GPS coordinates of each image. After the exterior elements of each image are determined in the GPS coordinate system, the initial image network is established. Finally, self-calibration bundle adjustment constrained by GPS coordinates is conducted to refine the image network. The proposed method is validated on three fields. Results confirm that the method can achieve good image network when accurate camera model parameters are unavailable.

scholarly journals Camera Model and Calibration Procedure for Oblique-Viewing Endoscope

2003 ◽  
pp. 373-381 ◽  
Author(s):  
Tetsuzo Yamaguchi ◽  
Masahiko Nakamoto ◽  
Yoshinobu Sato ◽  
Yoshikazu Nakajima ◽  
Kozo Konishi ◽  
...  
Keyword(s):  
Calibration Procedure ◽  
Camera Model

Probabilistic first ply failure prediction of composite laminates using a multi-scale M-SaF and Bayesian inference approach

2017 ◽  
Vol 52 (2) ◽  
pp. 169-195 ◽  
Author(s):  
Ghulam Mustafa ◽  
Afzal Suleman ◽  
Curran Crawford
Keyword(s):  
Bayesian Inference ◽  
Composite Laminates ◽  
Failure Criteria ◽  
Calibration Procedure ◽  
Strength Properties ◽  
Model Parameters ◽  
Successful Implementation ◽  
Damage State ◽  
Multi Scale ◽  
Unit Cells

This paper presents a probabilistic first ply failure analysis of composite laminates using a high-fidelity multi-scale approach called M-SaF (Micromechanics-based approach for Static Failure). To this end, square and hexagonal representative unit cells of composites are developed to calculate constituent stresses with the help of a bridging matrix between macro and micro stresses referred to as the stress amplification factor matrix. Separate failure criteria are applied to each of the constituents (fiber, matrix, and interface) in order to calculate the damage state. The successful implementation of M-SaF requires strength properties of the constituents which are the most difficult and expensive to characterize experimentally, limiting the use of M-SaF in the early design stages of a structure. This obstacle is overcome by integrating a Bayesian inference approach with M-SaF. An academic sample problem of a cantilever beam is used to first demonstrate the calibration procedure. Bayesian inference calibrates the M-SaF first ply failure model parameters as posterior distributions from the prior probability density functions drawn from lamina test data. The posterior statistics were then used to calculate probabilistic first ply failure for a range of different laminates.

scholarly journals DoF-Dependent and Equal-Partition Based Lens Distortion Modeling and Calibration Method for Close-Range Photogrammetry

Sensors ◽  
2020 ◽  
Vol 20 (20) ◽  
pp. 5934
Author(s):  
Xiao Li ◽  
Wei Li ◽  
Xin’an Yuan ◽  
Xiaokang Yin ◽  
Xin Ma
Keyword(s):  
Optical Axis ◽  
Focal Length ◽  
Calibration Method ◽  
Depth Of Field ◽  
Model Parameters ◽  
Lens Distortion ◽  
Camera Model ◽  
Distortion Model ◽  
Manual Adjustment ◽  
Close Range

Lens distortion is closely related to the spatial position of depth of field (DoF), especially in close-range photography. The accurate characterization and precise calibration of DoF-dependent distortion are very important to improve the accuracy of close-range vision measurements. In this paper, to meet the need of short-distance and small-focal-length photography, a DoF-dependent and equal-partition based lens distortion modeling and calibration method is proposed. Firstly, considering the direction along the optical axis, a DoF-dependent yet focusing-state-independent distortion model is proposed. By this method, manual adjustment of the focus and zoom rings is avoided, thus eliminating human errors. Secondly, considering the direction perpendicular to the optical axis, to solve the problem of insufficient distortion representations caused by using only one set of coefficients, a 2D-to-3D equal-increment partitioning method for lens distortion is proposed. Accurate characterization of DoF-dependent distortion is thus realized by fusing the distortion partitioning method and the DoF distortion model. Lastly, a calibration control field is designed. After extracting line segments within a partition, the de-coupling calibration of distortion parameters and other camera model parameters is realized. Experiment results shows that the maximum/average projection and angular reconstruction errors of equal-increment partition based DoF distortion model are 0.11 pixels/0.05 pixels and 0.013°/0.011°, respectively. This demonstrates the validity of the lens distortion model and calibration method proposed in this paper.

Uncertainty Estimation for the Optical System of Optical Measuring Machines

2014 ◽  
Vol 615 ◽  
pp. 95-101
Author(s):  
Jesús Caja ◽  
Emilio Gómez ◽  
Piera Maresca ◽  
Miguel Berzal
Keyword(s):  
Optical System ◽  
Calibration Procedure ◽  
Uncertainty Estimation ◽  
Geometric Distortion ◽  
Camera Model ◽  
Optical Measuring ◽  
The Monte Carlo Method ◽  
Measuring Machine ◽  
Machine Calibration ◽  
Distortion Parameters

This paper presents the problem of optical measuring machine calibration, emphasizing the calibration of the "optical system", omitting the calibration of the "machine system". The calibration of an optical measuring machine is the first step before using the instrument for any application. For this purpose, a mathematical model has been developed to transform the coordinates of a point in space (3D) into coordinates of a point in an image (2D). Using this camera model, a calibration procedure has been developed using a grid distortion pattern. Finally, a procedure for calculating the uncertainty of the camera and geometric distortion parameters based on the Monte Carlo method has been developed.

OPTIMAL MODEL FOR THE DIFFRACTION EFFECT IN THE ULTRASONIC FIELD OF PISTON TRANSDUCERS

2001 ◽  
Vol 09 (02) ◽  
pp. 461-476 ◽  
Author(s):  
ABDELLATIF BEY TEMSAMANI ◽  
STEVE VANDENPLAS ◽  
LEO VAN BIESEN
Keyword(s):  
Viscoelastic Material ◽  
Plane Waves ◽  
Viscoelastic Plate ◽  
Calibration Procedure ◽  
Ultrasonic Field ◽  
Model Parameters ◽  
Diffraction Effect ◽  
Optimal Function ◽  
Identification Approach ◽  
Attenuation And Dispersion

In this work, the analytical and experimental examination of the problem of diffraction effect is treated. In the laboratory, the diffraction phenomena have been mainly due to the beam spread of the ultrasonic plane wave propagating through a viscoelastic material. In fact, this effect has been found to be related, essentially to the attenuation and dispersion losses on a viscoelastic material. In this work, a frequency domain system identification approach is applied to determine an optimal function correcting the beam spread effect in both the normal and oblique incidences for a large frequency band (300 kHz–3 MHz). The Maximum Likelihood Estimator is applied to the magnitude and phase of the measured beam patterns of the used transducers in order to determine the model parameters. The calibration procedure is also discussed. Once the proposed model is established, the propagation through a viscoelastic plate is described and a comparison with measurements is done to validate the investigated model. The obtained longitudinal and shear attenuation and dispersion of the ultrasound in the viscoelastic plate are compared with those obtained by applying the complex harmonic plane waves combination model.

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