In a 3D profilometer by the fringe projection, the shadow will be produced inevitably, thus the fringes cannot be detected
in the region of the shadow. In addition, a smooth surface or a metal surface produces the specular reflection, and then,
no projection fringe can be recorded in the region of oversaturation on CCD. This paper reveals a proposed system for
improved these defects and shows some preliminary improved 3D profiles by the proposed dual fringe projection.
To obtain the profile of sample hided in the shadow and the oversaturation, this study used the dual-projection system by
two projectors. This system adopted two different directions of fringe projection and illuminates them alternately,
therefore, the shadow and the oversaturation produced in their corresponding locations. Two raw 3D profiles obtained
from taking the dual-projection by the four-step phase-shift. A set of algorithms used to identify the pixels of the shadow
and the oversaturation, and create an error-map. According to the error-map to compensate, two 3D profiles merged into
an error-reduced 3D profile. We used the solder paste as a testing sample. After comparatively analyzing the 3D images
obtained by our measurement system and by a contact stylus profilometer, the result shows that our measurement system
can effectively reduce the error caused by shadows and oversaturation.
Fringe projection system by using a projector is a non-contact, full field and quickly measuring system. The proposed
dual-projection by dual-projectors can effectively reduce the shadow and the oversaturation errors and enhance the scope
of application of the 3D contour detection, especially in the detection of precision structure parts with specular reflection.