Structured LightLecture 1

Matt Waibel

COMP 290-075

4-17-2000

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

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)

General Setup

• one camera• one light source

– types• slide projector

• laser

– projection• spot

• stripe

• pattern

Light Spot Projection 2D

imageplane

Light Spot Projection 2D

• Coordinates found by triangulation– can be found by projection geometry – d = b*sin()/sin( + )

– X0 = d*cos()

– Z0 = h = d*sin()

Light Spot Projection 3DZ

Light Spot Projection 3D

– X0 = (tan()*b*x)/(f + x*tan())

– Y0 = (tan()*b*y)/(f+x*tan())

– Z0 = (tan()*b*f)/(f+x*tan())

Light Stripe Projection

P

Static Light Pattern Projection

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

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

Binary Encoded Light Stripes

Binary Encoded Light Stripes

• Another Problem: How can we find the stripes in the images?

• Thresholding is dependent on the contrast

Segmenting Stripes

Segmenting Stripes

• Better Method:– Use the inverse image (opposite stripes) and

determine where the intensities intersect with the original image

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

3D Photography on Your Desk