3D profile measurement is widely used in many areas such as manufacturing, computer-aided design, virtual reality and medical diagnostics. As one of the core technologies in 3D profile measurement, digital fringe pattern projection is a highly sensitive noncontact technique for obtaining the 3D shape of an object. Then the grating pattern deformed by the measured object is captured by CCD cameras and decoded using appropriate algorithms so that the shape of the object can be deduced. In this paper, three sets of phase shift fringe patterns with different frequencies are projected on the surface of the measured object by a DLP projector and the deformed patterns are captured by two cameras. Then the four-step phase shift method is used to obtain the three groups of fringe patterns phases, and the three-frequency heterodyne method is adopted to unwrap the phase and obtain the absolute phase. The causes of the phase errors are analyzed and the subsequent compensation method of gamma correction of grating pattern is proposed to eliminate the main errors. Experiments are carried out and the results verify the accuracy and effectiveness of the proposed methods.
By establishing relevant coordinates of the Automatic Laser Navigation System, the basic principle of the system which
accesses the TBM three-dimensional reference point and yawing angle by mathematical transformation between TBM,
target prism and earth coordinate systems is discussed deeply in details. According to the way of rigid body descriptions
of its posture, TBM attitude parameters measurement and data acquisition methods are proposed, and measures to
improve the accuracy of the Laser Navigation System are summarized.
An on-line monitoring system for controlling the thickness and the flatness of NdFeB (Neodymium Ferrite Boron)
laminate components during the skiving process is reported. The on-line monitoring system mainly consists of a non-contact
eddy-sensor, a preamplifier, an A/D conversion card and a computer. The detailed description of the system with
respect to the connection between the probe and the grinder is provided. Practical on-line measurement and data
acquisition experiments are carried out. Experimental results indicate that the system principle is feasible and the
accuracy is up to μm order. The monitoring system can be used to improve conventional grinders that are widely
employed currently in China.
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