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CPSC 643 Robot Vision

CPSC 643 Robot Vision. Introduction to Computer Vision Dezhen Song, Department Computer Science and Engineering Texas A&M University Part of slides are from Bahadir K. Gunturk’s EE4780. Digital Image Acquisition. Imaging Sensors. Charge-Coupled Device (CCD). Imaging Sensors.

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CPSC 643 Robot Vision

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  1. CPSC 643 Robot Vision Introduction to Computer Vision Dezhen Song, Department Computer Science and Engineering Texas A&M University Part of slides are from Bahadir K. Gunturk’sEE4780

  2. Digital Image Acquisition

  3. Imaging Sensors • Charge-Coupled Device (CCD)

  4. Imaging Sensors • Complementary Metal Oxide Semiconductor (CMOS)

  5. CCD Vs. CMOS • Responsivity: CMOS >CCD • Dynamic range: CCD is 2 times better • Uniformity: CCD > CMOS • Shuttering • CCD: synchronous shutter (better) • CMOS: rolling shutter • Speed: CMOS >> CCD • Reliability: CMOS >>CCD • Cost: CMOS < CCD

  6. Matrix Representation of Images • A digital image can be written as a matrix

  7. RGB Color Model

  8. Dynamic range (Contrast Ratio) • Nature light: 1010:1 • Human eye: 109:1 • CMOS Sensor: 11000-6000:1 • LCD panel: 1000-10000:1

  9. Measured Dynamic Range

  10. Exposures Long exposure time Short exposure time

  11. Cameras • 2D camera (i.e. surveillance camera) • Pin-hole camera • Surveillance camera • Robotic pan-tilt-zoom camera • Wide angle camera – • fisheye, omni, etc • 1D camera (satellite camera, scanner) • Photo cell

  12. Perspective Projection • Perspective projection equations

  13. Pinhole Camera Model

  14. Cameras With Lenses • Most cameras are equipped with lenses. • There are two main reasons for this: • To gather light. • To keep the picture in sharp focus while gathering light from a large area.

  15. Real Lenses • Rays may not focus at a single point. Spherical aberration Spherical aberration can be eliminated completely by designing aspherical lenses.

  16. Real Lenses Chromatic Aberration

  17. Real Lenses • Special lens systems using two or more pieces of glass with different refractive indeces can reduce or eliminate this problem. However, not even these lens systems are completely perfect and still can lead to visible chromatic aberrations.

  18. Finite projective camera 11 dof (5+3+3)

  19. Camera Calibration

  20. Compound Lens Systems

  21. Lens modelling • Thin lens • Thick lens • Lens with mirrors • Radial Distortion

  22. Real Lenses Causes of distortion • Barrel Distortion & Pincushion Distortion Stop (Aperture) Chief ray (normal)

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