Intro to Computer Visio
Lecture 2
Greg Shakhnarovich
April 6, 2010
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Understanding Camera Design and Image Formation in Computer Vision, Lecture notes of Computer Vision
A lecture note from a computer vision course taught by greg shakhnarovich at the university of chicago in 2010. The lecture covers the basics of camera design, including the role of aperture and exposure time, and the geometry of pinhole cameras. It also discusses the impact of radial distortion on real lenses and methods for estimating and correcting distortion.
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Intro to Computer Visio
Lecture 2
Greg Shakhnarovich
April 6, 2010
Administrivia
Course webpage: http://ttic.edu/gregory/courses/vision
Planned policy: post lecture slides after each lecture.
Mailing list: https://mailman.cs.uchicago.edu/mailman/listinfo/cmsc I subscribed those officially enrolled; please make sure you are on the list (please subscribe if auditing or lurking!)
Camera design
Simplest camera: put sensor (film/CCD) in front of the object
Camera design
Simplest camera: put sensor (film/CCD) in front of the object
Camera design
Simplest camera: put sensor (film/CCD) in front of the object , shielded by a barrier with a small aperture
Camera design
Simplest camera: put sensor (film/CCD) in front of the object , shielded by a barrier with a small aperture
Camera obscura 17th century from Wikipedia
Camera design
Simplest camera: put sensor (film/CCD) in front of the object , shielded by a barrier with a small aperture
Camera obscura 17th century from Wikipedia
How does the aperture (pinhole diameter) affect the image?
How does exposure time affect the image?
Pinhole camera
Changing aperture size:
from S. Seitz’s slides
Pinhole camera
Changing aperture size:
from S. Seitz’s slides
Aperture too large: blur
Aperture too small: less light, difraction!
Thin lense model
f focal length, z 0 distance to object plane, zi distance to focal plane
1 z 0
zi
f
when z 0 → ∞, f ≈ zi
Moving focal plane by ∆zi moves image out of focus
Field of view determined by sensor size W vs. aperture size d
F -number f /# = fd
Pinhole camera geometry
Z
Y
X
C
u
v
W − 1
H − 1
image plane
d
optical axis
Image plane at Z = −d, “virtual” projection plane at Z = d
Pinhole camera geometry
Z
Y
X
C
u
v
W − 1
H − 1
image plane
d
optical axis
[X, Y, Z]
scene point
Image plane at Z = −d, “virtual” projection plane at Z = d
Pinhole camera geometry
Z
Y
X
C
u
v
W − 1
H − 1
image plane
d
[X, Y, Z]
scene point projection plane
v
u
O
d
optical axis
Image plane at Z = −d, “virtual” projection plane at Z = d Center of projection O at [0, 0 , d], with u = 0, v = 0
Pinhole camera geometry
Z
Y
X
C
u
v
W − 1
H − 1
image plane
d
[X, Y, Z]
scene point projection plane
v
u
O
d
optical axis
Image plane at Z = −d, “virtual” projection plane at Z = d Center of projection O at [0, 0 , d], with u = 0, v = 0