Master Thesis - Fachbereich Informatik

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5.3. EXPERIMENTAL RESULTS 109 Detection rate 1.05 1 0.95 0.9 0.85 0.8 black transparent 0.75 0 10 20 30 Tube spacing [mm] 40 50 60 Figure 5.5: Detection rate of black and transparent tubes depending on the spacing between consecutive tubes. Thus, one can conclude the system is able to detect the synthetic tube edges very accurate even under the presence of noise if there is a sufficient contrast between background and foreground. 5.3.2. Minimum Tube Spacing 10 black and 10 transparent tubes are used to investigate the influence of the spacing on the detection rate. The tubes have been placed on the conveyor at an approximately constant spacing. Five gap sizes are tested: 60, 30, 20, 10, and 5mm respectively. Each load of tubes passes the measuring area five times for each gap size at a conveyor velocity of 30m/min. In this experiment the total detection rate Ωtotal is considered only, i.e. how many tubes are detected by the system at least once. The results are averaged over the 5 iterations. As can be seen in Figure 5.5 the detection of black tubes is uncritical indicated by Ωtotal = 1 until the tube spacing is less than 10mm. This means no black tube can pass the measuring area without being measured if the spacing is ≥ 10mm. The decrease at 5mm gaps to Ωtotal =0.98 (i.e. 1 tube out of 50 is not detected) may be due to the fact that the manual tube placing can not guarantee an exact spacing of 5mm. It is likely that the distance between two tubes has become even smaller leading to the failure. Since the tests have been performed online it is not possible to locate the origin of the outlier. Therefore, it has been investigated how small the gap between two black tubes must be until the profile analysis fails to locate the tube. The results are shown in Figure 5.6. Even a spacing of about 2mm as in (a) is large enough to reliably detect the background regions between the tubes as can be also seen at the corresponding profile analysis results in (c). A gap of about 1mm, however, is too small even for black tubes. Due to perspective the points closer to the camera merge (see Figure 5.6(b) and (d)). Thetransparenttubesshowadetectionrateof< 1 even for the largest tested gap size of 60. This can be explained by the much lower contrast to the background. If the system must able to overcome a strong non-uniform background brightness, one has to make a larger compromise in terms of detection sensitivity. As it turns out there is no parameter setting that can guarantee that all tubes are detected independent of the gap
110 CHAPTER 5. RESULTS AND EVALUATION 300 250 200 150 100 50 (a) (b) smoothed profile segment boundaries local median global mean regional mean predicted tube boundaries 0 0 20 40 60 80 100 120 140 160 180 (c) 300 250 200 150 100 50 smoothed profile segment boundaries local median global mean regional mean 0 0 20 40 60 80 100 120 140 160 180 Figure 5.6: Minimum tube spacing for black tubes. (a) A spacing of about 2mm is still sufficient to locate the measurable tube correctly. (b) The detection fails if the two tubes appear to touch under perspective as on the left side. (c) Profile analysis of (a). (d) Profile analysis of (b). size. However, the results have shown that the detection rate decreases drastically below 10mm(seeFigure5.5). As the result of these experiments the minimum spacing used in the following experiments is 10mm for black tubes and 20mm for transparent tubes. 5.3.3. Conveyor Velocity The test data in this scenario includes 17 transparent and 21 black tubes of 50mm length and 8mm diameter. Manual ground truth measurements of these tubes are available. The number of tubes of each color is geared to the number of tubes that can be placed on the conveyor with a sufficient spacing. To increase the probability of a 100% detection rate, the spacing between two transparent tubes has to be larger than for black tubes. Each charge of tubes is measured 5 − 6 times at each velocity of 10, 20, 30, and 40m/min to yield a total number of > 100 measurements (based on even more single measurements) in each experiment. Thus, all tubes have to pass the measuring area many times. Before presenting the results in detail, Figure 5.7 shows an example of how the system has measured (a) the charge of black tubes and (b) the charge of transparent tubes at 20m/min respectively. Both the single measurements per tube (indicated by the crosses) as well as the computed total length and the corresponding ground truth length are visualized. The lengths measured by the system are quite close to the ground truth data. These results are just an example to show what kind of data is evaluated in the following. Since it is not possible to visualize longer sequences as detailed as in Figure 5.7 due to the (d)
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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
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1.5. THESIS OUTLINE 7 The vision pa
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2. Technical Background 2.1. Visual
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2.1. VISUAL MEASUREMENTS 11 (a) Fig
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2.1. VISUAL MEASUREMENTS 13 Figure
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2.1. VISUAL MEASUREMENTS 15 � xd
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2.2. ILLUMINATION 17 tubes alternat
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2.2. ILLUMINATION 19 effect of comp
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2.3. EDGE DETECTION 21 i 2 i 1 0 (a
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2.3. EDGE DETECTION 23 N × 1 kerne
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2.3. EDGE DETECTION 25 These operat
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2.3. EDGE DETECTION 27 (a) 0 ◦ (b
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2.4. TEMPLATE MATCHING 29 accuracy
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3. Hardware Configuration This chap
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3.2. CAMERA SETUP 33 3.2. Camera se
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3.2. CAMERA SETUP 35 eachcolorchann
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3.2. CAMERA SETUP 37 Figure 3.4: Co
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3.2. CAMERA SETUP 39 adjusting scre
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3.2. CAMERA SETUP 41 further distan
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3.3. ILLUMINATION 43 f V 12mm 129mm
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3.3. ILLUMINATION 45 (a) (b) (c) Fi
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3.3. ILLUMINATION 47 (a) (b) Figure
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3.4. BLOW OUT MECHANISM 49 A light
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4. Length Measurement Approach Whil
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4.2. MODEL KNOWLEDGE AND ASSUMPTION
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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
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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
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Page 120 and 121: 5.2. TEST SCENARIOS 105 enough, the
Page 122 and 123: 5.3. EXPERIMENTAL RESULTS 107 The t
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 134 and 135: 5.3. EXPERIMENTAL RESULTS 119 (a) (
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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.
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Master Thesis - Fachbereich Informatik

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