Master Thesis - Fachbereich Informatik

More documents

Recommendations

Info

4.2. MODEL KNOWLEDGE AND ASSUMPTIONS 53 (a) ‘empty’ (b) ‘entering’ (c) ‘leaving’ (d) ‘centered’ (e) ‘entering + centered’ (f) ‘ent. + centered + leav.’ (g) ‘centered + leaving’ (h) ‘entering + leaving’ (i) ‘full’ Figure 4.2: Potential image states. Each image can be categorized into one of these nine states. States that contain one tube completely with a clear spacing to neighboring tubes can be used for length measuring, i.e. state (d), (e), (f) and (g) respectively. The remaining states do not allow for a measurement and, thus, can be skipped. State (i) might be due to a too small field of view of the camera (i.e. tubes are too large), or to a failure in separation (i.e. the spacing between two or more tubes is missing). If this state is detected, a warning must be thrown. 4.2. Model Knowledge and Assumptions The visual length measurement of heat shrink tubes to be proposed throughout this chapter is based on several assumptions and model knowledge regarding the inspected objects, which is introduced in the following. 4.2.1. Camera Orientation As introduced in Section 3.2.2, the camera is placed above the conveyor. It must be adjusted to fulfill the following criteria: The optical ray is perpendicular to the conveyor The image plane is parallel to the conveyor This camera view is commonly denoted as fronto-parallel view [30]. If the image plane is parallel to the conveyor, the average scene depth is quite small. Therefore it is possible to approximate the perspective projection with a weak-perspective camera model. In this model (see Section 2.1.3) objects are projected onto the image plane up to a constant magnification factor. This means distances between two points lying in the same plane are preserved in the image plane until a constant scale factor. This property is important to allow for affine distance measurements in a fronto-parallel image view. 4.2.2. Image Content The following assumptions regard the image content and capture properties of the camera:
54 CHAPTER 4. LENGTH MEASUREMENT APPROACH (a) Ideal tube model (b) Perspective tube model Figure 4.3: (a) In the ideal model, the (parallel) projection of a 3D tube corresponds to a rectangle in the image. The distance d between the left and right edge is equal at each height. Under a perspective camera, objects closer to the camera appear larger in the image. Hence, the distance d1, belonging to the points on the tube edges that are closest to the camera, is larger than d2, and d2 is larger than d3 (the distance of the edge points that are farthest away). Note, the dashed lines are not visible in the image under back light, and the tube edges appear convex. Only one tube is visible completely (with left and right end) in each image at one time There is a clear spacing between two consecutive tubes The guide bars cover the upper and lower border of each image The guide bars are parallel and in horizontal direction The moving direction is from the left to the right The mean intensity of the background (conveyor belt) is brighter than the foreground (heat shrink tubes) There is a sufficient contrast between background and objects The video capture rate is fast enough to take at least one valuable image of each tube segment so that a length measurement can be performed. (Potentially the production speed has to be reduced to qualify this constraint) The image is not distorted, i.e. straight lines in the world are imaged as straight lines and parallel lines are also parallel in the image In this application, the variety of image situations to be observed is highly limited and constraint by the physical setup (see Chapter 3). Thus, it is possible to reduce the number of potential situations to nine defined states. Each image can be categorized into exactly one of these states as shown in Figure 4.2 by means of synthetic representatives. Only four of the nine states are measurable, i.e. state (d), (e), (f) and (g) respectively. In these states a tube is completely in the image. 4.2.3. Tubes Under Perspective Under ideal conditions, i.e. with a parallel projection, a tube on the conveyor is represented by a rectangle in the image plane with the camera setup used (see Figure 4.3(a)). Due
Page 1 and 2:
Fachbereich Informatik Department o
Page 4:
Acknowledgments First of all, I wou
Page 8 and 9:
Contents Acknowledgments iii Abstra
Page 10 and 11:
Contents ix 5.3.7. TubeLength .....
Page 12 and 13:
List of Tables 1.1. Rangeoftubetype
Page 14 and 15:
List of Figures 2.1. AccuracyandPre
Page 16 and 17:
1. Introduction Heat shrinkable tub
Page 18 and 19: 1.2. PROBLEM STATEMENT 3 hazards, r
Page 20 and 21: 1.4. RELATED WORK 5 Length [mm] Tol
Page 22 and 23: 1.5. THESIS OUTLINE 7 The vision pa
Page 24 and 25: 2. Technical Background 2.1. Visual
Page 26 and 27: 2.1. VISUAL MEASUREMENTS 11 (a) Fig
Page 28 and 29: 2.1. VISUAL MEASUREMENTS 13 Figure
Page 30 and 31: 2.1. VISUAL MEASUREMENTS 15 � xd
Page 32 and 33: 2.2. ILLUMINATION 17 tubes alternat
Page 34 and 35: 2.2. ILLUMINATION 19 effect of comp
Page 36 and 37: 2.3. EDGE DETECTION 21 i 2 i 1 0 (a
Page 38 and 39: 2.3. EDGE DETECTION 23 N × 1 kerne
Page 40 and 41: 2.3. EDGE DETECTION 25 These operat
Page 42 and 43: 2.3. EDGE DETECTION 27 (a) 0 ◦ (b
Page 44 and 45: 2.4. TEMPLATE MATCHING 29 accuracy
Page 46 and 47: 3. Hardware Configuration This chap
Page 48 and 49: 3.2. CAMERA SETUP 33 3.2. Camera se
Page 50 and 51: 3.2. CAMERA SETUP 35 eachcolorchann
Page 52 and 53: 3.2. CAMERA SETUP 37 Figure 3.4: Co
Page 54 and 55: 3.2. CAMERA SETUP 39 adjusting scre
Page 56 and 57: 3.2. CAMERA SETUP 41 further distan
Page 58 and 59: 3.3. ILLUMINATION 43 f V 12mm 129mm
Page 60 and 61: 3.3. ILLUMINATION 45 (a) (b) (c) Fi
Page 62 and 63: 3.3. ILLUMINATION 47 (a) (b) Figure
Page 64 and 65: 3.4. BLOW OUT MECHANISM 49 A light
Page 66 and 67: 4. Length Measurement Approach Whil
Page 70 and 71: 4.2. MODEL KNOWLEDGE AND ASSUMPTION
Page 72 and 73: 4.2. MODEL KNOWLEDGE AND ASSUMPTION
Page 74 and 75: 4.3. CAMERA CALIBRATION 59 4.2.7. B
Page 76 and 77: 4.3. CAMERA CALIBRATION 61 Figure 4
Page 78 and 79: 4.3. CAMERA CALIBRATION 63 is compu
Page 80 and 81: 4.4. TUBE LOCALIZATION 65 (a) (b) F
Page 82 and 83: 4.4. TUBE LOCALIZATION 67 � 1 Psm
Page 84 and 85: 4.4. TUBE LOCALIZATION 69 Global Th
Page 86 and 87: 4.4. TUBE LOCALIZATION 71 but also
Page 88 and 89: 4.4. TUBE LOCALIZATION 73 Global Re
Page 90 and 91: 4.5. MEASURING POINT DETECTION 75 f
Page 92 and 93: 4.5. MEASURING POINT DETECTION 77 T
Page 94 and 95: 4.5. MEASURING POINT DETECTION 79 -
Page 96 and 97: 4.5. MEASURING POINT DETECTION 81 0
Page 98 and 99: 4.5. MEASURING POINT DETECTION 83 o
Page 100 and 101: 4.5. MEASURING POINT DETECTION 85 (
Page 102 and 103: 4.5. MEASURING POINT DETECTION 87 w
Page 104 and 105: 4.6. MEASURING 89 side of the tube,
Page 106 and 107: 4.6. MEASURING 91 fcor(x) =−(c1x
Page 108 and 109: 4.7. TEACH-IN 93 inthemeasuringplan
Page 110 and 111: 4.7. TEACH-IN 95 The pair of a pixe
Page 112 and 113: 5. Results and Evaluation 5.1. Expe
Page 114 and 115: 5.1. EXPERIMENTAL DESIGN 99 between
Page 116 and 117: 5.1. EXPERIMENTAL DESIGN 101 where
Page 118 and 119:
5.1. EXPERIMENTAL DESIGN 103 Ground
Page 120 and 121:
5.2. TEST SCENARIOS 105 enough, the
Page 122 and 123:
5.3. EXPERIMENTAL RESULTS 107 The t
Page 124 and 125:
5.3. EXPERIMENTAL RESULTS 109 Detec
Page 126 and 127:
5.3. EXPERIMENTAL RESULTS 111 Lengt
Page 128 and 129:
5.3. EXPERIMENTAL RESULTS 113 GTD [
Page 130 and 131:
5.3. EXPERIMENTAL RESULTS 115 gray
Page 132 and 133:
Page 134 and 135:
5.3. EXPERIMENTAL RESULTS 119 (a) (
Page 136 and 137:
5.3. EXPERIMENTAL RESULTS 121 (a) (
Page 138 and 139:
Page 140 and 141:
5.3. EXPERIMENTAL RESULTS 125 Total
Page 142 and 143:
5.3. EXPERIMENTAL RESULTS 127 Color
Page 144 and 145:
5.3. EXPERIMENTAL RESULTS 129 Task
Page 146 and 147:
5.4. DISCUSSION AND FUTURE WORK 131
Page 148 and 149:
6. Conclusion In this thesis a func
Page 150:
Appendix 135
Page 153 and 154:
138 APPENDIX A. PROFILE ANALYSIS IM
Page 155 and 156:
140 APPENDIX A. PROFILE ANALYSIS IM
Page 157 and 158:
142 APPENDIX B. HARDWARE COMPONENTS
Page 159 and 160:
144 APPENDIX B. HARDWARE COMPONENTS
Page 161 and 162:
146 Bibliography [18] C. Demant, B.
Page 163 and 164:
148 Bibliography [51] K.K. Pingle.
show all

Master Thesis - Fachbereich Informatik

Create successful ePaper yourself

Delete template?

Save as template?