1. Structured Lighting Guido Gerig, Univ. of Utah
CS 6320, 3D Computer Vision
Spring 2012
(thanks: some slides S. Narasimhan CMU, Marc Pollefeys UNC)

2. Active Stereo
Active manipulation of scene: Project light pattern on object. Observe geometry of pattern via camera → 3D geometry

3. Real-Time 3D Model Acquisition
The SIGGRAPH Paper:
Full paper as PDF.
One-page abstract and Figure 1 as PDF.
Two-page abstract and Figure 1 as PDF.
A 5-minute video describing the system:
AVI file, 640 x 480 pixels (19MB)
RealVideo stream, 640 x 480 pixels, 1536 kbs
RealVideo stream, 320 x 240, kbs
SIGGRAPH 2002 talk:
Talk as PPT
Embedded video clip: sig02_begin_m.avi
Embedded video clip: sig02_recap.avi
Embedded video clip: turtle2.avi
[Video clip of hand moving object, then view of screen. 40 secs, no sound]
Here is a new pipeline that *is* designed for fast feedback to the user. The user moves the object around by hand (notice the black glove so we don’t get fingers in the scan). You can always see the current state of the model on the screen, and can move the object to fill any holes.
Link:

4. General Setup one camera one light source types projection
slide projector
laser
projection
spot
stripe
pattern

5. (thanks: some slides S. Narasimhan CMU, Marc Pollefeys UNC)
Structured Lighting
Guido Gerig
CS 6320, 3D Computer Vision
Spring 2012
(thanks: some slides S. Narasimhan CMU, Marc Pollefeys UNC)

6. Light Spot Projection Assume point-wise illumination by laser beam
Given the equation
of the projection line LP
and p, the image of P ,
we can solve for P w.r.t.
the camera frame.
image
plane p

7. 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
Courtesy S. Narasimhan, CMU

8. Active Stereo (Structured Light)
rectified
CSc D Computer Vision / Ioannis Stamos
From Sebastian Thrun/Jana Kosecka

9. Triangulation Light Plane Project laser stripe onto object Object
Camera
The first stage in the real-time pipeline is the range scanner. It’s based on the idea of triangulation. In the simplest case, this consists of projecting a stripe of light onto a scene, looking at it from an angle…
Project laser stripe onto object
Courtesy S. Narasimhan, CMU

10. Triangulation Light Plane Image Point
Object
Laser
Camera
Image Point
Plug X, Y into plane equation to get Z
… and triangulating between a plane from the point of view of the light source and a ray from the point of view of the camera. In the simplest case of a laser triangulation scanner, this yields data from a single contour on the object at a time, and you can sweep the line across the surface to stack up a bunch of these contours and get a scan of an entire patch of surface.
Depth from ray-plane triangulation:
Intersect camera ray with light plane
Courtesy S. Narasimhan, CMU

11. CSc83029 3-D Computer Vision / Ioannis Stamos
Triangulation
Light Stripe System.
Light Plane:
AX+BY+CZ+D=0
(in camera frame)
Image Point:
x=f X/Z, y=f Y/Z
(perspective) Yc Zc Xc
Image
Triangulation: Z=-D f/(A x + B y + C f)
Move light stripe or object.
CSc D Computer Vision / Ioannis Stamos

12. Example: Laser scanner
Cyberware® face and head scanner
+ very accurate < 0.01 mm
− more than 10sec per scan

13. Microsoft Kinect Details are not publicly available
The Kinect combines structured light with two classic computer vision techniques: depth from focus, and depth from stereo. It does not use RGB camera!.
Details are not publicly available

14. Microsoft Kinect

15. Low-Cost 3D Scanner for Everyone

16. Low-Cost 3D Scanner for Everyone

17. Excellent Additional Materials
Course notes:
Slides:
Source code: