In this study, a laser line auto-scanning system was designed to perform underwater close-range 3D reconstructions with high accuracy and resolution. The system changes the laser plane direction with a galvanometer to perform automatic scanning and obtain continuous laser strips for underwater 3D reconstruction. The system parameters were calibrated with the homography constraints between the target plane and image plane. A cost function was defined to optimize the galvanometer’s rotating axis equation. Compensation was carried out for the refraction of the incident and emitted light at the interface. The accuracy and the spatial measurement capability of the system were tested and analyzed with standard balls under laboratory underwater conditions, and the 3D surface reconstruction for a sealing cover of an underwater instrument was proved to be satisfactory.

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For a long time the complete measurement of parts with complex structure and features has been a bottleneck of 3D measurement in reverse engineering. This paper presents a laser sensor that is mainly composed of three CCD cameras and four laser line projectors. With the principle of projecting laser planes from three directions and receiving the reflected stripes from the other three directions, the sensor can measure complicated parts from multi views. A concise approach for calibrating the sensor is proposed. The orientation of each laser plane is determined first. Then according to the orientation calibration points in the laser plane are generated as an array by controlling the CMM to let the laser plane intersect with a single-tooth target. The 2D coordinate system in the laser plane is established with the axes parallel to the line and row of the array. Thus the extrinsic calibration of the sensor is avoided. The 2D data in a laser plane can be obtained from a CCD image after the relationship between the laser plane and the CCD image is solved using the calibration points. Finally the 2D data in three laser planes are merged by transforming them into a world coordinate system. Experimental studies show that the developed sensor possesses good accuracy, and a complicated part can be measured as long as it can be accessed from at least one view.

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