Structured Light Lecture 1

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Structured LightLecture 1

• Matt Waibel
• COMP 290-075
• 4-17-2000

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Overview

• Background
• General Setup
• Light Point Projection 2D and 3D
• Light Stripe Projection
• Static Light Pattern Projection
• Binary Encoded Light Stripes
• Segmenting Stripes
• 3D Photography on Your Desk

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Background

• Intersecting the projection ray with an
  additional ray or plane will lead to a unique
  reconstruction of the object point
• Structured Light projection of light patterns
  into a scene (active method)

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General Setup

• one camera
• one light source
• types
• slide projector
• laser
• projection
• spot
• stripe
• pattern

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Light Spot Projection 2D
image plane
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Light Spot Projection 2D

• Coordinates found by triangulation
• b can be found by projection geometry
• d bsin(a)/sin(a b)
• X0 dcos(b)
• Z0 h dsin(b)

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Light Spot Projection 3D
Z
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Light Spot Projection 3D

• X0 (tan(a)bx)/(f xtan(a))
• Y0 (tan(a)by)/(fxtan(a))
• Z0 (tan(a)bf)/(fxtan(a))

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Light Stripe Projection
P
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Static Light Pattern Projection
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Static Light Pattern Projection

• Project a pattern of stripes into the scene to
  reduce the total number of images required to
  reconstruct the scene
• Problem how to uniquely identify light stripes
  in the camera image when several are
  simultaneously projected into the scene

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Binary Encoded Light Stripes

• Set of light planes are projected into the scene
• Individual light planes are indexed by an
  encoding scheme for the light patterns
• Obtained images form a bit-plane stack
• Bit-plane stack is used to uniquely address the
  light plane corresponding to every image point

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Binary Encoded Light Stripes
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Binary Encoded Light Stripes
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Segmenting Stripes

• Another Problem How can we find the stripes in
  the images?
• Thresholding is dependent on the contrast

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Segmenting Stripes

• Better Method
• Use the inverse image (opposite stripes) and
  determine where the intensities intersect with
  the original image

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3D Photography on Your Desk

• Method that uses very common tools to do 3D
  photography
• Requirements PC, camera, stick, lamp, and a
  checker board
• Uses weak structured light approach

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3D Photography on Your Desk