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Machine vision


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This is a research presentation I did for my Optics class at Michigan Technological University.

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Machine vision

  1. 1. Machine Vision<br />Optics in Manufacturing<br />By: Dan Ehlke<br />February 25, 2009<br />
  2. 2. What is Machine Vision ?<br />Application of Computer vision to industry & manufacturing<br />Machine Vision is a subfield of engineering that incorporates:<br />computer science<br />optics<br />mechanical engineering<br />industrial automation<br />
  3. 3. Machine Vision Application<br />inspection of manufactured goods such as:<br />semiconductor chips<br />automobiles<br />food <br />Pharmaceuticals<br />and more . . .<br />
  4. 4. Machine Vision Capabilities<br />Checks for:<br />Gauging or measurement : Dimensions<br />Serial numbers<br />Presence of components<br />Pattern matching<br />Blob analysis or Edge detection<br />Optical character recognition (OCR) <br /> and barcode decoding<br />Surface inspection<br />Colour analysis<br />
  5. 5. General Process<br /> 1. Image Capture<br /> 2. Image Preprocessing<br /> 3. Definition of one or more (manual) regions of interest<br /> 4. Segmentation of the objects<br /> 5. Computation of object features<br /> 6. Decision as to the correctness of the segmented objects <br />
  6. 6. Typcial System<br />1 or more digital cameras (CCD or CMOS sensor)<br />Optics : Lenses / mirrors<br />Light Sources<br />Input / Output hardware<br />Synchronizing Trigger sensor<br />Actuator<br />A program<br />
  7. 7. Image Capture<br />note the difference between a vector & bitmap image<br />
  8. 8. Vector vs Bitmap<br />Example: .SVG<br />Line vectors & coordinates<br />Bezier curve<br />Example: JPEG<br />Pixels<br />Grid of values<br />
  9. 9. Lighting<br />Front Lighting<br />Best for surface items<br />Print<br />Etched numbers<br />Back Lighting<br />Better contrast for:<br />Gauging<br />positioning<br />Ring lighting<br />Intense, shadow-free lighting along optical axis<br />Directional<br />Picking out surface effects<br />Diffused<br />Better for positioning<br />Less shadows & reflections<br />Polarized light<br />With polarized lens on camera<br />Polarizing back lighting can even render surface tensions visible<br /><ul><li>Infrared or Ultraviolet</li></li></ul><li>Cameras<br />A video camera produces analog signal that is digitized by a frame grabber<br />captures individual still images<br />Linescan camera<br />
  10. 10. Multiple Cameras<br />Part handling is simplified - part moves through on conveyor<br />Part orientation is not required<br />Inspection is done without slowing manufacturing line<br />Only minimal spacing between parts is required<br />
  11. 11. Multiple cameras<br />Processing of the image <br />
  12. 12. Image Processing<br />Regions of Interest (ROIs) limit the information being analyzed. <br />
  13. 13. Lenses<br />Entocentric<br /> magnification changes, due to object displacement<br /> image distortion<br /> perspective errors<br /> poor image resolution<br /> object edge position uncertainty, due to lighting geometry<br />Telecenric<br />the front lens must be at least as large as the object largest dimension <br />Larger<br />heavier <br />more expensive than common optics.<br />Perecentric<br />
  14. 14. Telecentric Lens<br />Magnification constancy<br />In Measurement applications, an orthonormal view is commonly desired for correct measurement.<br />
  15. 15. Telecentric Lens<br />Perspective Errors Limited<br />
  16. 16. Telecentric Lens<br />image size remains almost unchanged when the object distance changes<br />image size remains almost unchanged when the object distance changes<br />
  17. 17. Telecentric Lens<br />Distortion<br />Depends upon distance of object as well as the optics<br />Trapezoidal Distortion<br />Difficult to calibrate out because it is asymmetrical<br />Radial Distorsion<br />No Distortion<br />
  18. 18. Telecentric Lens<br />Resolution<br />Telecentric Lens<br />
  19. 19. Telecentric Lens<br />No edge position uncertainty<br />
  20. 20. Perecentric Lens<br />3D peripheral vision of objects without any aid of mirrors.<br /> Just 1 camera makes the job of 4 or more cameras placed around and over the object<br />No image matching, typical of “multi-point” imaging systems, is necessary<br />All the orthogonal sides have the same magnification because the object is seen from its top, not from one side<br />Space between the object and the lens is left in order to enable the passing of pieces in on line applications<br /> Almost any kind of illumination source can be integrated<br />
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  22. 22. The Processmaster 5G automatic inspection system is installed upstream of the kiln to inspect either green or biscuit tiles, preferably before and after glazing. Defective tiles are immediately identified and removed from the production process. Costs for glazing and firing of defective products are dramatically reduced and reject tiles are recycled back into the raw materials, further optimising the production process.<br />
  23. 23. Resources<br /><br /><br /><br /><br /><br />
  24. 24.<br /><br />