Contents | 6 |
Abstract | 11 |
Symbols | 12 |
Chapter 1 Introduction | 14 |
1.1 Motivation | 14 |
1.2 Outline | 15 |
1.3 Contribution | 17 |
Chapter 2 Modelling the camera mapping | 18 |
2.1 Geometric optics for computer vision | 18 |
2.1.1 The “thin lens” assumption and first order optics | 18 |
2.1.2 The circle of confusion | 21 |
2.1.3 Image acquisition | 22 |
2.1.3.1 The sensor array | 22 |
2.1.3.2 A simplified sensor model | 24 |
2.1.3.3 The sensor array as coordinate system | 25 |
2.2 The pinhole camera model | 26 |
Definition 2.2.1 | 26 |
Definition 2.2.2 (Pinhole camera) | 27 |
2.3 Third order optics and thick lenses | 28 |
Remark 2.3.1 (Chromatic aberrations) | 29 |
2.4 The pinhole camera model with distortion | 30 |
2.4.1 Definition | 30 |
Definition 2.4.1 (Distortion model) | 30 |
Remark 2.4.2 | 30 |
Definition 2.4.3 (Pinhole camera with distortion) | 30 |
2.4.2 Radial distortion | 31 |
Definition 2.4.4 (Radial distortion) | 32 |
2.4.3 Radius transformations | 32 |
2.4.4 Other distortion functions | 34 |
2.4.4.1 Misaligned thin lens | 34 |
2.4.4.2 Misaligned lens systems | 35 |
2.5 Inverting the camera mapping | 36 |
Definition 2.5.1 (undistortion, re-projection) | 36 |
Remark 2.5.2 | 36 |
2.6 The pinhole camera model in homogeneous co-ordinates | 38 |
Remark 2.6.1 | 38 |
Remark 2.6.2 | 39 |
Lemma 2.6.3 | 39 |
Chapter 3 Error functions for camera calibration and 3D reconstruction | 40 |
3.1 Introduction | 40 |
3.2 Projective and re-projective error | 40 |
Definition 3.2.1 (Projective Error) | 41 |
Definition 3.2.2 (Re-projective Error) | 41 |
3.3 Euclidean error | 42 |
Definition 3.3.1 (Euclidean error) | 42 |
Definition 3.3.2 (Normalized Euclidean error) | 42 |
Remark 3.3.3 | 43 |
Remark 3.3.4 (In front of and behind the camera) | 44 |
3.4 Error functions for camera calibration and 3D-reconstruction | 47 |
3.4.1 Calibration error functions | 47 |
Remark 3.4.1 (Root mean square error) | 48 |
Remark 3.4.2 (Existence of an optimal solution) | 48 |
Remark 3.4.3 (Complete Calibration) | 50 |
3.4.2 Reconstruction error functions | 50 |
Remark 3.4.4 | 50 |
3.5 Non-linear optimization | 51 |
Chapter 4 Initial values for camera calibration problems | 53 |
4.1 Introduction | 53 |
4.2 The two stage method of Tsai | 55 |
4.3 An initial image transformation by direct linear transformation | 60 |
Remark 4.3.1 (negative values for | 62 |
Remark 4.3.2 | 62 |
4.4 An initial image transformation from homogra-phies | 63 |
4.4.1 Introduction | 63 |
4.4.2 Two necessary conditions for planar targets | 63 |
Remark 4.4.1 | 64 |
4.4.3 Zhang’s initial value | 65 |
Remark 4.4.2 (Minimal number of observations) | 66 |
4.4.4 An initial image transformation with known center and zero skew | 67 |
Remark 4.4.3 ( | 67 |
4.4.5 An initial image transformation with known aspect ratio and no skew | 68 |
4.4.6 An initial image transformation with known aspect ratio and unknown skew | 69 |
Remark 4.4.4 | 70 |
4.4.7 An initial image transformation with no skew | 71 |
4.4.7.1 A straight forward constraint | 71 |
4.4.7.2 A solution by a linear least squares problem with Cholesky decom-position | 72 |
4.4.8 Experimental results | 73 |
4.4.8.1 Overview | 73 |
4.4.8.2 Simulations | 74 |
4.5 An initial value for the extrinsic camera param-eters | 77 |
4.5.1 Introduction and problem statement | 77 |
4.5.2 Standard pose estimation | 77 |
4.5.3 An algebraic re-projective approach for regular grids | 78 |
4.5.4 An optimal solution w.r.t. Euclidean error for 1D targets | 83 |
4.6 An initial solution for the distortion | 85 |
4.6.1 Introduction | 85 |
Remark 4.6.1 (Initial distortion for the re-projective error) | 85 |
4.6.2 Zhang’s initial solution for the radial distortion | 85 |
4.6.3 An optimal initial solution for all distortion parameters | 87 |
Remark 4.6.2 | 89 |
4.7 Camera calibration with distortion as a semi-linear problem | 90 |
4.7.1 Parameter reduction by semi-linear optimization | 90 |
4.7.2 Experimental results | 91 |
4.7.2.1 Results for the normal setup | 92 |
4.7.2.2 Results for the webcam setup | 98 |
4.7.2.3 Results for the wide angle setup | 102 |
Chapter 5 Calibration of a stereo camera system | 104 |
5.1 Introduction | 104 |
5.2 Epipolar geometry | 104 |
Definition 5.2.1 (fundamental matrix, essential matrix) | 105 |
5.3 Epipolar Curves | 108 |
Definition 5.3.1 (Generalized Epipolar Constraint) | 108 |
Remark 5.3.2 ( | 108 |
5.4 Stereo camera calibration with multiple targets | 110 |
5.5 Extrinsic stereo camera calibration with gener-alized epipolar constraints | 111 |
5.5.1 A two step algorithm | 111 |
i. Calculate the positions of the calibration plate with respect to the reference coordinate system | 111 |
ii. Calculate the position of the right camera | 113 |
5.5.2 A one step algorithm | 113 |
5.5.3 Application and results | 114 |
5.6 Extrinsic stereo camera calibration with respect to the projective error | 116 |
5.7 Extrinsic and intrinsic stereo camera calibration | 118 |
Chapter 6 Non-standard camera models | 120 |
6.1 Introduction | 120 |
6.2 Feature point extraction | 123 |
6.2.1 Standard feature point extraction | 123 |
6.2.2 Model based extraction of isolated squares | 126 |
6.2.3 Appropriability of the feature point extraction methods | 130 |
6.2.3.1 Appropriability with respect to the sensor model | 130 |
6.2.3.2 Appropriability with respect to the camera model | 130 |
6.3 The residual distortion | 132 |
6.3.1 The point spread function by first order optics | 132 |
6.3.2 Other sources of residual distortion | 139 |
6.3.3 Experimental results | 139 |
6.4 Spline correction | 147 |
6.4.1 Motivation and related work | 147 |
6.4.2 A depth-dependent distortion term | 147 |
Definition 6.4.1 ( | 147 |
6.4.3 Depth-dependent distortion correction for the projective and re-projective error function | 148 |
6.4.4 The tensor spline space | 148 |
Definition 6.4.2 (Tensor product) | 149 |
Definition 6.4.3 (B-spline base) | 149 |
Definition 6.4.4 ( | 150 |
Definition 6.4.5 ( | 150 |
6.4.5 Tensor splines for the re-projective depth-dependent dis-tortion | 150 |
6.4.6 Spline correction for the Euclidean error | 151 |
6.4.7 The viewing ray for spline corrected cameras | 152 |
6.4.8 Spline correction for stereo reconstruction | 152 |
6.4.9 Disadvantages of the spline correction | 153 |
6.5 A two-plane distortion model | 157 |
6.5.1 Motivation and related work | 157 |
6.5.2 The plane | 158 |
Definition 6.5.1 | 158 |
6.5.3 Distortion mappings in | 159 |
Definition 6.5.2 (Distortion model w.r.t. the two-plane distortion) | 160 |
6.5.4 The re-projection w.r.t. the two-plane distortion | 160 |
Definition 6.5.3 ( | 160 |
Remark 6.5.4 (One-plane distortion is a subset of the two-plane distortion) | 161 |
6.5.5 Error functions for the two-plane distortion model | 161 |
6.5.5.1 The projective error | 162 |
6.5.5.2 The Euclidean error | 162 |
Definition 6.5.5 (Euclidean error) | 162 |
6.5.5.3 The projected Euclidean error | 163 |
Definition 6.5.6 (projected Euclidean error) | 163 |
Remark 6.5.7 (A projective error for the two-plane distortion model) | 163 |
6.5.5.4 The normalized Euclidean error | 163 |
Definition 6.5.8 (normalized Euclidean error) | 164 |
6.5.5.5 Depth-dependence of the two-plane distortion model | 166 |
6.5.6 Calibration algorithm | 168 |
6.6 A generic multi-plane camera | 169 |
6.6.1 Introduction and related work | 169 |
6.6.2 From the image to a reference coordinate system | 169 |
6.6.3 Tensor spline approximation of the coordinate transfor-mation | 172 |
6.6.4 A calibration setup for the generic multi-plane camera | 172 |
6.7 Experimental results | 174 |
6.7.1 Setup | 174 |
6.7.1.1 Calibration setup for the standard camera model | 174 |
6.7.1.2 Calibration setup for the spline correction | 174 |
6.7.1.3 Calibration setup for the two-plane distortion model | 174 |
6.7.2 Results for spline corrected cameras | 175 |
6.7.2.1 Prototype reconstruction | 175 |
6.7.2.1.1 In-plane spline correction | 175 |
6.7.2.1.2 3d spline correction | 177 |
6.7.2.2 Stereo reconstruction | 184 |
6.7.3 Results for the two-plane distortion model | 186 |
6.7.3.1 Stereo reconstruction | 186 |
6.7.3.2 Point to point error | 186 |
6.7.3.3 Angles of reconstructed planes | 190 |
6.7.3.4 Other test series | 193 |
Standard), | 193 |
Two-Plane) | 193 |
One-Plane). | 193 |
6.7.3.5 Planarity test | 200 |
6.7.3.6 Prototype reconstruction | 205 |
Standard), | 205 |
One-Plane), | 205 |
3d2dSpline, | 205 |
Two-Plane). | 205 |
Chapter 7 Conclusions | 210 |
Bibliography | 212 |
Index | 224 |