Master Thesis - Fachbereich Informatik

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3.3. ILLUMINATION 47 (a) (b) Figure 3.10: (a) Installation of the back light panel. The measuring area is illuminated from below through a translucent conveyor belt. A diffuser is used to yield a more uniform light and to protect the fiber optical light panel. (b) SCHOTT PANELight Backlight A23000 used for illumination (Source: SCHOTT). application. On the contrary it has the effect of less light entering the camera which yields darker images and increases the amount of sensor noise. As result of the experiments with different lighting techniques, the back lighting setup has been chosen for the prototype. It offers excellent properties for black tubes and yielded also very good results for the transparent tubes in connection with a fine structured, translucent conveyor belt. The incident lighting did not perform better in the experiments. A light source (SCHOTT DCR III) with a DDL halogen lamp (150W, 20V) has been selected in combination with the fiber optic area light (SCHOTT PANELight Backlight A23000) (see Figure 3.10(b)). The panel size is 102 × 152mm. It is installed 20mm below a cut-out in the conveyor below the belt as can be seen in Figure 3.10(a). A diffuser between light panel and conveyor belt provides a uniform illumination and protects the light area against dirt. More details regarding the illumination hardware can be found in Appendix B.2. The usage of a fiber optic area light below the conveyor belt has the advantage of a very low heat development since the light source can be placed outside at a certain distance. With respect to the characteristics of heat shrink tubes, the avoidance of heat is essential at this step to prevent deformations. The light is transmitted through a flexible tube of fibers. If the lamp is out of order it can be exchanged easily without changing anything at the conveyor. The lifetime of one halogen lamp is about 500 hours at maximum brightness. To eliminate the influence of illumination from other light sources than the back light, the whole measuring area including the camera is darkened. This guarantees constant illumination conditions. For the prototype, a wooden rack has been constructed that is placed around the measuring area on the conveyor. A thick black, non translucent fabric can be spanned around the rack leaving only two openings where the tubes enter and leave
48 CHAPTER 3. HARDWARE CONFIGURATION Figure 3.11: Air pressure is used to sort out tubes that do not meet the tolerances. The blow out unit consisting of an air blow nozzle, light barrier and a controller (not visible in the image) is placed at a certain distance behind the measuring area. the function room darkening. For industrial use this interim solution has to be replaced by a more robust and compact (metal) case that excludes environmental illumination and protects the whole measuring system against other outside influences in addition. A slight overpressure inside the closed case or an air filtering system could be integrated to avoid dust particles from entering the case through the required openings. Any accumulation of dust or other dirt on the lens is critical and must be prevented. 3.4. Blow Out Mechanism After a tube has passed the measuring area the measured length is evaluated with respect to the given target length and tolerance. The result is a binary good/bad decision for each particular tube. Good tubes are allowed to pass the blow out unit, which is placed behind the measuring area at a certain distance. On the other hand, tubes that do not meetthetoleranceshavetobesortedout. Thisisdonebyairpressure. Aairblownozzle is arranged to blow out tubes from the conveyor. Therefore, the guide bars have to end behind the measuring area. The whole blow out setup can be seen in Figure 3.11. The visual inspection system sends the good/bad decision over a RS-232 connection (serial interface) to a controller unit in terms of a certain character followed by a carriage return (‘\r’). The used protocol can be seen in Table 3.4. Once the controller receives an A or B this message is stored in a first-in-first-out (FIFO) buffer. Message Code TUBE GOOD ‘A\r’ TUBE BAD ‘B\r’ RESET ‘Z\r’ Table 3.4: Protocol used for communication between the inspection system and the blow out controller.
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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 .....
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 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 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
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5. Results and Evaluation 5.1. Expe
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5.1. EXPERIMENTAL DESIGN 99 between
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5.1. EXPERIMENTAL DESIGN 101 where
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5.1. EXPERIMENTAL DESIGN 103 Ground
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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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