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散斑是激光三角传感器测量不确定度极限的根本影响因素。提出了一种用于旋转对称激光三角传感器的激光散斑的仿真方法,获得了仿真散斑图像。在旋转对称的三角传感器中,投射的激光点在检测器上被成像为一个环,从而散斑也相应是圆弧形。研究了散斑的特性,该散斑在环的半径方向上服从主观散斑的特性,其尺寸由光学系统的数值孔径决定。而在环的切线方向上,其本质上是客观散斑,由于光学系统存在折返光路,其尺寸由物体到检测器的光程、投射的激光光斑尺寸和成像圆环的半径决定。实验结果表明,仿真结果与散斑理论一致。基于仿真给出了对旋转对称三角传感器位移测量不确定度极限的分析,结果表明,使用旋转对称形式的传感器光学布局,在相同的光学系统数值孔径和使用同样的灰度质心算法的情况下,可达到传统激光三角测量不确定度的1/5。
Speckle is the fundamental determinant of the measurement uncertainty of laser triangulation sensors. A simulation method of laser speckle for rotationally symmetric laser triangulation sensor was proposed and the speckle image was obtained. In a rotationally symmetric triangle sensor, the projected laser spot is imaged as a ring on the detector so that the speckle is also circular arc-shaped. The speckle characteristics are studied. The speckle obeys the characteristic of subjective speckle in the radial direction of the ring, and its size is determined by the numerical aperture of the optical system. In the tangential direction of the ring, it is essentially an objective speckle, which is determined by the optical path from the object to the detector, the size of the projected laser spot, and the radius of the imaging ring due to the presence of the re-entrant optical path in the optical system. Experimental results show that the simulation results are consistent with speckle theory. Based on the simulation, the limit of the uncertainty of displacement measurement of rotationally symmetric triangle sensor is given. The results show that the sensor optical layout of rotational symmetry can be used in the same numerical aperture of optical system and the same gray centroid algorithm, Can reach the traditional laser triangulation uncertainty of 1/5.