Master Thesis - Fachbereich Informatik

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4.2. MODEL KNOWLEDGE AND ASSUMPTIONS 57 Figure 4.5: The image intensity of transparent tubes is not uniform as for black tubes. Depending on how much light can pass through a tube, regions appear darker or brighter. One characteristic of transparent tubes under back light are two dark horizontal stripes at the top and the bottom of a tube indicated by the arrows. The printing also reduces the translucency and thus appears darker in the image. 4.2.6. Tube Orientation The tube orientation is highly constrained by the guide bars as introduced in Section 3.1. Thus, an approximately horizontal orientation can be assumed throughout the design of the inspection algorithms. In practice, the distance between the guide bars is slightly larger than the outer diameter of a tube to prevent a blockage, since tubes may not be ideally round. This means, the cross-section of a tube can be elliptical instead of circular. Let dspace denote the vertical distance between the guide bar distance dGB, and hmax the maximum expected tube extension in vertical direction with respect to the image projection. The remaining spacing distance can be expressed as dspace = dGB − hmax ascanbeseeninFigure4.6(a). The maximum possible rotation is reached if the tube hits both guide bars at two points (see Figure 4.6(b)). The maximum angle of rotation θmax can be defined as the angle between the longitudinal axis of the tube and the x-axis. One can define an unrotated version of the tube with the longitudinal axis parallel to the x-axis and shifted so that the two axis intersect at the center of gravity of the rotated tube. In Figure 4.6(b) this virtual tube is visualized as dashed rectangle. The distance between the measuring points of the rotated and the ideal horizontal tube can be also seen in the Figure and are denoted as dL and dR for the left and right tube side respectively. Both dL and dR are ≤ dspace/2. If thetubeisnotbent,dL = dR. The maximum error between the ideal distance l and the rotated distance l ′ can be estimated as follows: errθ = l ′ − l � (4.1) = l2 + d2 space − l For example, in a typical setup for 50mm tubes of 8mm diameter one tube has a length of approximately 415 pixels and dspace = 15. This leads to an error of errθ =0.27pixel. Thus, with one pixel representing 0.12mm in the measuring plane, the acceptable maximum error due to orientation would be about 0.03mm. On average this error will be even smaller. Based on these estimation, the orientation error is neglected in the following, i.e. all tubes are assumed to be oriented ideally horizontal.
58 CHAPTER 4. LENGTH MEASUREMENT APPROACH (a) (b) Figure 4.6: (a) The guide bar distance dGB and the maximum extension of a tube in vertical direction hmax define the maximum space between a tube and the guide bars dspace at ideal horizontal orientation. (b) The maximum possible tube orientation is limited by the guide bars. The angle θ between the longitudinal axis of the tube and the ideal measuring distance parallel to the x-axis determines the maximum distance the measuring point can be displaced by rotation (dL = dR ifthetubeisnotbent).Thisdistanceis≤ dspace/2 and can be used to estimate the error due to rotation between the ideal tube length l andtherotateddistancel ′ .
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Fachbereich Informatik Department o
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Acknowledgments First of all, I wou
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Contents Acknowledgments iii Abstra
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Contents ix 5.3.7. TubeLength .....
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List of Tables 1.1. Rangeoftubetype
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List of Figures 2.1. AccuracyandPre
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1. Introduction Heat shrinkable tub
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1.2. PROBLEM STATEMENT 3 hazards, r
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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 68 and 69: 4.2. MODEL KNOWLEDGE AND ASSUMPTION
Page 70 and 71: 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
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5.3. EXPERIMENTAL RESULTS 107 The t
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5.3. EXPERIMENTAL RESULTS 109 Detec
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5.3. EXPERIMENTAL RESULTS 111 Lengt
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5.3. EXPERIMENTAL RESULTS 113 GTD [
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5.3. EXPERIMENTAL RESULTS 115 gray
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5.3. EXPERIMENTAL RESULTS 119 (a) (
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5.3. EXPERIMENTAL RESULTS 121 (a) (
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5.3. EXPERIMENTAL RESULTS 125 Total
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5.3. EXPERIMENTAL RESULTS 127 Color
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5.3. EXPERIMENTAL RESULTS 129 Task
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5.4. DISCUSSION AND FUTURE WORK 131
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6. Conclusion In this thesis a func
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Appendix 135
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138 APPENDIX A. PROFILE ANALYSIS IM
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140 APPENDIX A. PROFILE ANALYSIS IM
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142 APPENDIX B. HARDWARE COMPONENTS
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144 APPENDIX B. HARDWARE COMPONENTS
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146 Bibliography [18] C. Demant, B.
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148 Bibliography [51] K.K. Pingle.
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Master Thesis - Fachbereich Informatik

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