光线弯曲对激光测量热钢板厚度的影响

Influence of Laser Beam Bending on Thickness Measurement of Hot Steel Plate

以无热源大平面空气壁模型,用传热学理论计算了大平面热钢板附近空气的一维温度分布,从而得到了大平面热钢板附近空气的一维折射率分布。利用光线折射理论,求出了光线的传输路径和像点的偏离量。分析和计算表明:当钢板温度、测量角和测量距离等参数增大时,像点偏离值就随着增大。对于钢板激光测厚系统,采用单表面单光路时,光线弯曲引起的测量误差较大,并且基本不随测量厚度减小而减小。采用完全对称的双面双光路时,左右光路的像点偏离正好抵消,光线弯曲引起的测量总误差很小,而且随测量厚度减小而减小。

With large plane air space without heat source as model, the one-dimension temperature distribution of air near a large plane hot steel plate is calculated by heat transfer theory and one-dimension refractive index distribution of air near the large plane hot steel plate is obtained. The deviation value of light-ray from transmission path and image point is obtained by using light-ray refractive theory. The analysis and calculation show that the deviation value of image point will be increased when steel plate temperature, measuring angle and measuring distance, etc increase. For a laser thickness-measuring system for steel plate, when single surface single light path is applied, the measuring error caused by light-ray bending will be larger and it will basically not be reduced with the measured thickness reduction. When a full symmetric double-surface double light path is applied, the image point deviation in left and right light path just offset. The total measuring error caused by light-ray bending is very little and it will be reduced with the measured thickness reduced.