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.

scholarly journals EXPERIMENTS ON CALIBRATING TILT-SHIFT LENSES FOR CLOSE-RANGE PHOTOGRAMMETRY

2016 ◽  
Vol XLI-B5 ◽  
pp. 99-105 ◽  
Author(s):  
E. Nocerino ◽  
F. Menna ◽  
F. Remondino ◽  
J.-A. Beraldin ◽  
L. Cournoyer ◽  
...  
Keyword(s):  
Optical Axis ◽  
National Research Council ◽  
Image Plane ◽  
Limiting Factors ◽  
Depth Of Field ◽  
Small Object ◽  
Digital Cameras ◽  
Close Range Photogrammetry ◽  
Object Distance ◽  
Close Range

One of the strongest limiting factors in close range photogrammetry (CRP) is the depth of field (DOF), especially at very small object distance. When using standard digital cameras and lens, for a specific camera – lens combination, the only way to control the extent of the zone of sharp focus in object space is to reduce the aperture of the lens. However, this strategy is often not sufficient; moreover, in many cases it is not fully advisable. In fact, when the aperture is closed down, images lose sharpness because of diffraction. Furthermore, the exposure time must be lowered (susceptibility to vibrations) and the ISO increased (electronic noise may increase). In order to adapt the shape of the DOF to the subject of interest, the Scheimpflug rule is to be applied, requiring that the optical axis must be no longer perpendicular to the image plane. Nowadays, specific lenses exist that allow inclining the optical axis to modify the DOF: they are called tilt-shift lenses. In this paper, an investigation on the applicability of the classic photogrammetric model (pinhole camera coupled with Brown’s distortion model) to these lenses is presented. Tests were carried out in an environmentally controlled metrology laboratory at the National Research Council (NRC) Canada and the results are hereafter described in detail.

Measurement of Cam Spacing on Assembled Camshaft Based on Improved Fundamental Matrix Calibration

2013 ◽  
Vol 850-851 ◽  
pp. 241-244
Author(s):  
Guan Nan Li ◽  
Qing Chang Tan ◽  
Si Yuan Liu
Keyword(s):  
Fundamental Matrix ◽  
Ccd Camera ◽  
Calibration Method ◽  
Measurement Model ◽  
Pinhole Camera ◽  
Epipolar Line ◽  
Camera Model ◽  
Distortion Model ◽  
Imaging Model ◽  
Measurement Results

Imaging model of double CCD camera based on pinhole camera model and distortion model is introduced, and the fundamental matrix is presented. Distortion model is led into the fundamental matrix calibration. Based on the imaging model of Z. Zhangs calibration method, fundamental matrix is carried out. Pixel coordinate for calibration is modified by cameras interior parameters and distortion coefficients. Base on the imaging model of double CCD camera, measurement model for cam spacing is established. Cam spacing is measured by the feature of cam edge. In experiments, accurate pixel coordinates of model plane were used in calibration. The distance between a point and its corresponding epipolar line was estimated as the error. The measurement results show that the accuracy of proposed method satisfied the monitoring requirements of the axial positioning error of the cam piece.

scholarly journals Depth-Dependent High Distortion Lens Calibration

Sensors ◽  
2020 ◽  
Vol 20 (13) ◽  
pp. 3695 ◽  
Author(s):  
Carlos Ricolfe-Viala ◽  
Alicia Esparza
Keyword(s):  
Camera Calibration ◽  
Calibration Method ◽  
Complex Problem ◽  
Lens Distortion ◽  
Lens Model ◽  
Distortion Model ◽  
Calibration Methods ◽  
Depth Dependency ◽  
Division Model

Accurate correction of high distorted images is a very complex problem. Several lens distortion models exist that are adjusted using different techniques. Usually, regardless of the chosen model, a unique distortion model is adjusted to undistort images and the camera-calibration template distance is not considered. Several authors have presented the depth dependency of lens distortion but none of them have treated it with highly distorted images. This paper presents an analysis of the distortion depth dependency in strongly distorted images. The division model that is able to represent high distortion with only one parameter is modified to represent a depth-dependent high distortion lens model. The proposed calibration method obtains more accurate results when compared to existing calibration methods.

scholarly journals EXPERIMENTS ON CALIBRATING TILT-SHIFT LENSES FOR CLOSE-RANGE PHOTOGRAMMETRY

2016 ◽  
Vol XLI-B5 ◽  
pp. 99-105 ◽  
Author(s):  
E. Nocerino ◽  
F. Menna ◽  
F. Remondino ◽  
J.-A. Beraldin ◽  
L. Cournoyer ◽  
...  
Keyword(s):  
Optical Axis ◽  
National Research Council ◽  
Image Plane ◽  
Limiting Factors ◽  
Depth Of Field ◽  
Small Object ◽  
Digital Cameras ◽  
Close Range Photogrammetry ◽  
Object Distance ◽  
Close Range

One of the strongest limiting factors in close range photogrammetry (CRP) is the depth of field (DOF), especially at very small object distance. When using standard digital cameras and lens, for a specific camera – lens combination, the only way to control the extent of the zone of sharp focus in object space is to reduce the aperture of the lens. However, this strategy is often not sufficient; moreover, in many cases it is not fully advisable. In fact, when the aperture is closed down, images lose sharpness because of diffraction. Furthermore, the exposure time must be lowered (susceptibility to vibrations) and the ISO increased (electronic noise may increase). In order to adapt the shape of the DOF to the subject of interest, the Scheimpflug rule is to be applied, requiring that the optical axis must be no longer perpendicular to the image plane. Nowadays, specific lenses exist that allow inclining the optical axis to modify the DOF: they are called tilt-shift lenses. In this paper, an investigation on the applicability of the classic photogrammetric model (pinhole camera coupled with Brown’s distortion model) to these lenses is presented. Tests were carried out in an environmentally controlled metrology laboratory at the National Research Council (NRC) Canada and the results are hereafter described in detail.

Camera Calibration Method Based on OpenCV

2013 ◽  
Vol 330 ◽  
pp. 517-520 ◽  
Author(s):  
Yu Jing Qiao ◽  
Zhong He Liu ◽  
Da Xun Hu ◽  
Jing Wei Xu
Keyword(s):  
Least Square Method ◽  
Calibration Method ◽  
Intersection Point ◽  
Least Square ◽  
External Parameter ◽  
Lens Distortion ◽  
Camera Model ◽  
Initial Value ◽  
Original Matrix ◽  
Distortion Parameters

A new calibration method is proposed on the basic of OpenCV camera model and existing calibration method. The method can be accomplished in three concerted steps. Firstly, standardization homography matrix is obtained through camera linear model namely normalized the elements in lower right corner of the original matrix, then the intrinsic parameters matrix and external parameter initial value of camera can be calibrated through solving the statically indeterminate equations with the least square method. Secondly, concerning lens distortion, nonlinear model is obtained, and using intersection point coordinate of chess board and initial value of the first step, initial value of distortion parameters is given through the least square method. Finally, all the camera parameters will nonlinear optimized.

A Camera Calibration Method Using Quadratic Curve Fitting

2012 ◽  
Vol 591-593 ◽  
pp. 1281-1284
Author(s):  
Tian Xia ◽  
Chao Jin ◽  
Xiao Yang Jiang ◽  
Yi Zhong Li
Keyword(s):  
Camera Calibration ◽  
Curve Fitting ◽  
Calibration Method ◽  
Model Parameters ◽  
Feature Points ◽  
Camera Model ◽  
Quadratic Curve ◽  
Camera Image ◽  
Concentric Circles ◽  
The Relationship

The camera calibration is an essential part in the machine vision,the camera calibration is to establish the relationship between the camera image pixellocation and scene position,the approach is based on the camera model,solving the model parameters of the camera image coordinates and world coordinates from the known feature points. Using the camera calibration method based on quadratic curve,this article selects a template consists of two concentric circles and two concentric ovals.We shot 4 images in different directions,and use different combinations of three of the four images to calibrate camera.Thus we can calculatethe various parameters of the camera.

Camera Calibration Method Based on Circle Plane Board

2013 ◽  
Vol 475-476 ◽  
pp. 184-187
Author(s):  
Wen Guo Li ◽  
Shao Jun Duan
Keyword(s):  
Camera Calibration ◽  
Calibration Method ◽  
Lens Distortion ◽  
Edge Extraction ◽  
Circle Plane ◽  
Circle Centre ◽  
Extraction Algorithm ◽  
Calibration Algorithm ◽  
Characteristic Points ◽  
Distortion Parameters

We present a camera calibration method based on circle plane board. The centres of circles on plane are regarded as the characteristic points, which are used to implement camera calibration. The proposed calibration is more accurate than many previous calibration algorithm because of the merit of the coordinate of circle centre being obtained from thousand of of edge pionts of ellipse, which is very reliable to image noise caused by edge extraction algorithm. Experiments shows the proposed algorithm can obtain high precise inner parameters, and lens distortion parameters.

Study on Mechanical Properties of the Composite Materials Film by Speckle Projection Method

2012 ◽  
Vol 496 ◽  
pp. 281-284
Author(s):  
Wen Wen Liu ◽  
Zhi Wang ◽  
Yun Hai Du ◽  
Xian Zhong Xu ◽  
Da Quan Liu ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Composite Material ◽  
Composite Materials ◽  
Projection Method ◽  
Dynamic Deformation ◽  
Calibration Method ◽  
Deformation Measurement ◽  
Lens Distortion

An improved accurate speckle projection method is used for study the mechanical properties of the composite material film in the paper. A system for deformation measurement is developed with the telecentric lenses, in which such conventional lens’ disadvantages such as lens distortion and perspective error will be diminished. Experiments are performed to validate the availability and reliability of the calibration method. The system can also be used to measure the dynamic deformation and then results are also given.

Fisheye Lens Distortion Calibration Based on the Lens Charactetic Curves

2014 ◽  
Vol 519-520 ◽  
pp. 636-639
Author(s):  
Bao Long Zhang ◽  
Shao Jing Zhang ◽  
Wei Qi Ding ◽  
Hui Shuang Shi
Keyword(s):  
Optical System ◽  
Characteristic Curve ◽  
Calibration Method ◽  
Lens Distortion ◽  
Wide Angle ◽  
Forming Process ◽  
Fisheye Lens ◽  
Large Scope ◽  
Wide Angle Lens ◽  
Barrel Distortion

The fisheye lens is a kind of ultra wide angle lens, which can produce a big super-wide-angle lens distortion. In order to cover a large scope of light, barrel distortion is artificially added to the optical system. However, in some cases this distortion is not allowed, then it requires calibrations of those distortions. Most of the traditional distortion calibration method uses target plane calibration to do it. This paper discusses the way of design fisheye lens, through which we can know the forming process of distortion clearly. Based on this paper, a simple and effective calibration method can be understood. Different from common camera calibration method, the proposed calibration method can avoid the error occurring in the process of calibrating test, that directly use the lens’ characteristic curve. Through multiple sets of experimental verifications, this method is effective and feasible.

Pixel-wise distortion model and its calibration method for AMCW LiDAR

2021 ◽  
Author(s):  
Junwoo Jason Son ◽  
Youngbin Son ◽  
Byeongho Song ◽  
Soohee Han
Keyword(s):  
Calibration Method ◽  
Distortion Model
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