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UEC Int’l Mini-Conference No.53 3

Fourier transform profilometry for high precision projection

Shuo ZHAN *1 and Yoko MIYAMOTO 2

1 UEC Exchange Study Program (JUSST Program)
2 Institute for Advance Science, the University of Electro-Communications
The University of Electro-Communications, Tokyo, Japan

Abstract

The principles of structured light and three-dimensional measurement are widely applied in three-
dimensional optical measurement applications, such as industrial part defect detection, humanbody
3D modeling, computer vision, and image processing. Among the various techniques based on these
principles,Fourier transform profilometry is a fundamental and widely used measurement method.
However,due to its relatively simple measurement approach, it cannot achieve precise measurement
and 3D reconstruction of surfaces with rapid variations. In this paper, we first introduced the basic
principles of Fourier transform profilometry. We then perform image processing on interferograms
using MATLAB.We apply fourier transform profilometry to the processed interferogram to obtain
a 3D reconstruction image.Due to the existence of gamma nonlinearity in digital projectors(DLP),
high order harmonics will appear in deformed fringes, which may lead to spectrum aliasing and
measurement errors. Therefore, using a method based on fringe intensity statistical analysis, the
gamma value of DLP is obtained and fed back to DLP, so that the structure fringe with good sinusoidal
property can be projected, which can suppress the occurrence of higher harmonics in the deformed
fringe and ensure the measurement accuracy of FTP. The comparison experiment between the two
cases with and without gamma correction proves that the former is better than the latter.

Keywords: Fourier transform profilometry,3D shape measurement, Phase measurement,phase
unwrap- ping,Gamma correction

1 Introduction three-dimensional DIC technology. However,
because the modeling process of DIC technol-
Digital image correlation method is a mechani- ogy depends on the similarity of matching sub-
cal analysis method of non-contact optical de- regions, when the camera binocular Angle is too
tection based on computer developed in the large or the surface structure of the object is
1980s. Thanks to the rapid development of com- complex, the matching accuracy will be reduced
puter technology, it has become one of the most or even the subinterval will be decorrelated, and
successful methods for detecting efficiency in the the iterative convergence cannot be completed,
field of optical inspection [1–3]. This technol- resulting in the reconstruction failure [5]. At
ogy uses the acquisition system to obtain the the same time, three-dimensional measurement
change of fringe information before and after de- technology in geological mapping, machine vi-
formation, and then uses the digital image cor- sion, cultural relics identification, medical biol-
relation method to analyze and process, and re- ogy, targets Detection, reverse engineering and
alizes the accurate measurement of surface de- other fields have a wide range of applications
formation through digital calculation [4].In or- [6–10].Therefore, in order to make full use of the
der to realize full field three-dimensional defor- ability of fringe projection technology to recon-
mation measurement, scientists have proposed struct the three-dimensional topography of com-
plex structures, and solve the problem that it
The author is supported by JUSST Scholarship.
* can not achieve accurate deformation tracking,