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’s EE4780

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
Bahadir K. Gunturk

7. RGB Color Model

8. Dynamic range (Contrast Ratio)
Nature light: 1010:1
Human eye: 109:1
CMOS Sensor: :1
LCD panel: :1

9. Measured Dynamic Range
Bit Precision of A/D Converter
Contrast Ratio 8
256:1 10
1024:1 12
4096:1 14
16384:1 16
65536:1

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
Bahadir K. Gunturk

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.
Bahadir K. Gunturk

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

19. Camera Calibration

20. Compound Lens Systems
Bahadir K. Gunturk

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)