Structured Light Range Imaging

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• Structured Light Range Imaging
• Lecture 17

(Thanks to Content from Levoy, Rusinkiewicz,
Bouguet, Perona, Hendrik Lensch)
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3D Scanning
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Stereo Triangulation
I
J
Correspondence is hard!
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Structured Light Triangulation
I
J
Correspondence becomes easier!
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Structured Light

• Any spatio-temporal pattern of light projected
  on a surface (or volume).
• Cleverly illuminate the scene to extract scene
  properties (eg., 3D).
• Avoids problems of 3D estimation in scenes with
  complex texture/BRDFs.
• Very popular in vision and successful in
  industrial applications (parts
• assembly, inspection, etc).

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Light Stripe Scanning Single Stripe
Light plane
Source
Camera
Surface

• Optical triangulation
• Project a single stripe of laser light
• Scan it across the surface of the object
• This is a very precise version of structured
  light scanning
• Good for high resolution 3D, but needs many
  images and takes time

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Triangulation
Light Plane
Object

• Project laser stripe onto object

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Triangulation
Light Plane
Object
Laser
Image Point

• Depth from ray-plane triangulation
• Intersect camera ray with light plane

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Example Laser scanner
Cyberware face and head scanner
very accurate lt 0.01 mm - more than 10sec
per scan
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Example Laser scanner
Digital Michelangelo Project http//graphics.stanf
ord.edu/projects/mich/
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3D Model Acquisition Pipeline
3D Scanner
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3D Model Acquisition Pipeline
3D Scanner
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3D Model Acquisition Pipeline
3D Scanner
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3D Model Acquisition Pipeline
3D Scanner
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3D Model Acquisition Pipeline
3D Scanner
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3D Model Acquisition Pipeline
3D Scanner
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http//graphics.stanford.edu/projects/mich/
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Great Buddha of Nara
http//www.cvl.iis.u-tokyo.ac.jp/gallery_e/nara-hp
/nara.html
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Scanning and Modeling the Cathedral of Saint
Pierre, Beauvais, France
http//www1.cs.columbia.edu/allen/BEAUVAIS/
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Portable 3D laser scanner (this one by Minolta)
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Faster Acquisition?

• Project multiple stripes simultaneously
• Correspondence problem which stripe is which?
• Common types of patterns

• Binary coded light striping
• Gray/color coded light striping

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Binary Coding
Faster stripes in
images.
Projected over time
Example 3 binary-encoded patterns which allows
the measuring surface to be divided in 8
sub-regions
Pattern 3
Pattern 2
Pattern 1
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Binary Coding

• Assign each stripe a unique illumination
  codeover time Posdamer 82

Time
Space
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Binary Coding
Example 7 binary patterns proposed by Posdamer
Altschuler
Projected over time

Pattern 3
Pattern 2
Pattern 1
Codeword of this píxel 1010010 ? identifies the
corresponding pattern stripe
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More complex patterns
Works despite complex appearances
Works in real-time and on dynamic scenes

• Need very few images (one or two).
• But needs a more complex correspondence algorithm

Zhang et al
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Real-Time 3D Model Acquisition
http//graphics.stanford.edu/papers/rt_model/
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Captured video (30Hz)
Captured video (3000Hz)
Reconstruction (30Hz)
Reconstruction (120Hz)
Reconstruction different view (120Hz)
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Captured video (30Hz)
Captured video (3000Hz)
Reconstruction (30Hz)
Reconstruction (120Hz)
Reconstruction different view (120Hz)
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Continuum of Triangulation Methods
Slow, robust
Fast, fragile
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Microsoft Kinect
IR Camera
IR LED Emitter
RGB Camera
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Microsoft Kinect
Depth map
Speckled IR Pattern
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3D Acquisition from Shadows
Bouguet-Perona, ICCV 98
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Fluorescent Immersion Range Scanning
http//www.mpi-inf.mpg.de/resources/FIRS/
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Fluorescent Immersion Range Scanning
http//www.mpi-inf.mpg.de/resources/FIRS/
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Structured Light Reconstruction

• Avoid problems due to correspondence
• Avoid problems due to surface appearance
• Much more accurate
• Very popular in industrial settings
• Reading
• Marc Levoys webpages (Stanford)
• Katsu Ikeuchis webpages (U Tokyo)
• Peter Allens webpages (Columbia)