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UEC Int’l Mini-Conference No.53 9
era can introduce fringe distortion, while phase
variations between fringes are highly suscepti-
ble to noise interference. Additionally, the mea-
surement speed is constrained by the imaging
speed of the acquisition equipment, and filter-
ing operations may result in the loss of high-
frequency information carried by the object. In
fringe projection measurement, the nonlinear re-
sponse of optical system and camera may cause
(a) the fringe image to deviate from the ideal sinu-
soidal waveform, thus affecting the accuracy of
phase calculation. By introducing gamma com-
pensation, the nonlinear distortion can be cor-
rected to make the projection fringe closer to the
theoretical model and improve the measurement
accuracy. However, overcompensation may re-
sult in loss of image detail, so the gamma value
should be properly set according to the charac-
teristics of the system.
(b)
Figure 12: Model reconstruction before and af- 5 Conclusions
ter gamma correction. (a) Before gamma correc-
tion (without compensation). (b) Post-gamma The filtering process cannot eliminate all noise;
correction. efforts should be made to minimize noise in-
troduction during projection.In the simulation
Table 1: The running time of gamma error com- experiments, we need to examine the choice of
pensation(s) filtering and shifting parameters to remove the
large slope in the reconstructed 3D shape.
Compensation Way Running Time As the projection device of FTP measurement
No Compensation 15.21 system, DLP brings great convenience and flex-
Gamma Error Compensation 6.32 ibility to measurement, but because of the
gamma nonlinearity of DLP itself, the measure-
ment accuracy is reduced. In this paper, a
proposed algorithm is obviously shortened, the gamma correction method is used, which can not
processing time of compensation phase is re- completely suppress the nonlinear effect of DLP
duced, and the efficiency of 3D measurement on the measurement, but can ensure the mea-
is improved. According to the analysis in Fig- surement accuracy of FTP to a certain extent.
ure 12, the forehead and eyes of the model have The 3D surface shape of the object can be ac-
higher accuracy in reconstruction due to gamma curately reconstructed when FTP measurement
error compensation. is performed after gamma correction of DLP. At
the same time, it is necessary to use gamma cor-
rection for DLP in FTP measurement. The high
4 Discussion
precision gamma correction method needs to be
further discussed.
During MATLAB simulation of interferograms,
several factors can lead to a loss of modeling
accuracy. When using sinusoidal fringe pro- 6 Acknowledgments
jection, the actual fringe images may deviate
from the ideal sinusoidal waveform. Variations Thanks to Yoko Miyamoto and his affiliated lab-
in the angle between the projector and cam- oratory for their support and guidance. Thanks
