measurement of free-formed surfaces

8/14/2019 Measurement of Free-Formed Surfaces

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How to measure and describe

Free-Formed Surfaces

Measurement of free-formed surfaces

(2008-10-23/30)

Graphic Science

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Measurement and description of free-formed surfaces


Description of free-formed surfaces

Moire fringe method

SPG: Stereo Photogrammetry()

Three dimensional degitizer

Space curve

NURBS (Non-Uniform Rational B-Spline)

Description and generation of surfaces

Application

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Moire Fringe Method

Principle

Moire fringe contour

Objects shape from Moire fringe

Experimental results

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Surface representation

with Moire fringe

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d

L d/(1)

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grid interval Moire fringe produced with two

diffraction grids

Moire fringe

bright

bright

brightdark

dark

darkL

L

dark

6Geometric relations in Moire measurement

camera

light source screen Moire fring

bright stripe

dark stripe


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ns

d

nn

2

22

s

d

,

11

s

d

(2)

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Distance between the Moire fringe and the screen, n

light source

screen

lensimage plane

intersection between the n-th

fringe and the grids shadow


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Experimental set upMoire fringe pattern obtained from

the experiment9

light source 1 light source 2

screen

camera

Difference of the measures obtained from the Moire and the stereo-photogrammetry

methods 10

(a) contours (b) sections (c) improved Moire methods


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2 Stereo-photographic measurement

2 Principle

2 Application


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)1/()( 87654 YaXaaYaXay

15

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)1/()( 87654 iiiii YaXaaYaXay

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ConclusionThe minimum numbers of markers

necessary for the stereo-photogrammetry are;

More than fiducial markers

and control markers

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2

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Measurement of the femoral

surface of human knee

Check the numbers of the fiducial

and control markers

()


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Measurement of the cartilage thickness of the

human patellar surface

1) Measure the patellar surface2) Dissolve the cartilage with a regent (3) Measure the surface without cartilage

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()

Measurement of the cartilage

thickness of the human

patellar surface

Check the numbers of the fiducial

and control markers


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3 Terminology

3 Contact type digitizer

33 Non-contact type digitizer

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3 Three dimensional (3D) digitizer


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Prototype of digitizer

by Wismans (1980)

specimen

dialgauge

dialgauge

dialgauge

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Application to archeology

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mouse with a cord winding around

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Objects shape measurement with a laser

scanner and its reconstruction

hands

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guess what it is

? ? ?

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AssignmentSubmit a short report explaining about the principle

of a triangular surveyingA4page

measurement of free-formed surfaces

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