Line structured light 3D measurement technology for pipeline microscratches based on telecentric lens

Abstract

We propose a line structured light 3D measurement technology for pipeline microscratches based on a telecentric lens that realizes the 3D measurement of microscratches on the pipeline surface. A method for calibrating the light plane normal vector under the telecentric camera model is proposed. This method only needs to consider the orientation information in the light plane calibration without involving position information, which avoids the difficulty of calibrating the light plane due to the insensitivity of the telecentric camera to the depth changes of the object along the optical axis. The self-adaptive convolution-mass method is used to extract the centerline points of the light stripe with speckles. Finally, the 3D coordinates of the intersection of the light plane and the measured surface are reconstructed. A line structured light micromeasurement platform based on a telecentric lens was built. Experiments show that the maximum standard deviation of the measurement is 2.0 μm, and the maximum error of the average value of repeated measurements is 0.3 μm, indicating that the measurement platform has high accuracy that meets the requirements for the measurement of the microscratch depth of pipelines in industrial applications.