ppt课件
22
Vanishing points and lines
Parallel lines in the world intersect in the image at a “vanishing point”
ppt课件
23
Vanishing points and lines
Vanishing Line
Vanishing Pointo
oVanishing Point
ppt课件
24
Vanishing points and lines
Vanishing line
Vertical vanishing point
(at infinity)
Vanishing point
Slide from Efros, Photo from Criminisi
• Many methods have been developed using this approach. • Major advantage -- simple to use. • Low spatial resolution -- patterns become sparser with
distance. • Some close range (4cm) sensors exist with good depth
have an inadequate depth resolution (1cm at best) for most practical industrial vision purposes.
29
Structured Light Methods
• Project patterns of light (grids, stripes, elliptical patterns
How high is the camera?
What is the camera rotation? What is the focal length of the camera?
Which ball is closer?
ppt课件
15
Dimensionality Reduction Machine (3D to 2D)
3D world
2D image
Point of observation
ppt课件
16
Figures © Stephen E. Palmer, 2002
Projection can be tricky…
Slide source: Seitz
ppt课件
17
Projection can be tricky…
Laser ranging works on the principle that the surface of the object reflects laser light back towards a receiver which then measures the time (or phase difference) between transmission and reception in order to calculate the depth.
resolution (around 0.05mm) but have very narrow field of view and close range of operation.
30
Moire Fringe Methods
• A moire projection system
31
Moire Fringe Methods
etc.) onto an object.
• Surface shapes are then deduced from the distortions of the patterns that are produced on Object's Surface.
• Knowing relevant camera and projector geometry, depth can be inferred by triangulation.
ppt课件
Vanishing point
25
Vanishing points and lines
ppt课件
26
Photo from online Tate collection
Note on estimating vanishing points
ppt课件
27
Laser Ranging Systems
Projective Geometry
What is lost?
• Length • Angles
Parallel?
Perpendicular?
ppt课件
21
Projective Geometry
What is preserved?
• Straight lines are straight
28
Laser Ranging Systems
Most laser rangefinders: • Work at long distances (greater than
15m) • Consequently their depth resolution is
inadequate for detailed vision tasks. • Shorter range systems exist but still
Slide source: Seitz
ppt课件
18
Projective Geometry
What is lost?
• Length
Who is taller?
Which is closer?
ppt课件
19
Length is not preserved
ppt课件
A’ C’ B’
20 Figure by David Forsyth
3D Computer Vision
Dr. Shengyong Chen Email: sy@
Introduction
• The eyes • Methods of 3D Vision
14
Today’s class: Camera and World Geometry
How tall is this woman?