Line-shaped beam based Doppler distance sensors enable 3D inspection of rotating rough surfaces for instance in working lathes by a simultaneous, multipoint velocity and distance measurement. To minimize the systematic error of the measurement, this work presents a high-accuracy 3D model and calibration of the interferometric fringe volume of the sensors. The model is derived from the Gaussian beam expression and applied to describe fringe geometry distribution throughout the intersection volume of two paraxial Gaussian beams. A full-field fringe spacing calibration using a high-resolution matrix camera is performed with two line-shaped beams as a demonstration, which shows an average relative difference of below 0.6% to the modeling result.
Laser triangulation ranging sensors, with their micron precision, simple principles and compact structures, are widely applied in the industry for instance for workpiece shape and defect measurements. However, the determination of system parameters for laser triangulation sensors currently depends on the experience and manual attempts of designers, which is not only time-consuming but also enables additional measurement errors. In this work, we present a genetic algorithm based method to accurately, fast, and adaptively determine the optimal system parameters for various measurement requirements. Based on the Scheimpflug principle, measurement range and resolution expressions are first derived for laser triangulation systems. The formulas of laser spot size in the x- and y-directions of image detectors are presented and the system geometric dimension is constrained when setting the measured surface on the calibration reference plane. Furthermore, a nonlinear programming genetic algorithm (NP-GA) is proposed to evaluate system parameters for certain measurement conditions, in which the local search capability is significantly improved with rapid convergence to the optimal solution. The algorithm allows determining the parameters by setting diverse measurement resolutions with a relative uncertainty below 3.7% in 3 s. ZEMAX simulations of the sensor systems are performed with non-sequential mode to validate NP-GA determined system parameters. Simulation and computed results show the relative differences of the parameters dependent RMS radius of the laser spot on the image detector are below 0.35% and 8.72% in the x- and y-directions, respectively.
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