激光粒度测量中,当样品到透镜的轴向距离较大时,由于透镜口径有限,会因渐晕而降低测量的精度和准确度。针对这种问题,应用灰色系统理论事先检验数据,来判断渐晕点位置,然后通过建模对渐晕点后的衍射光能信号进行灰预测,从而修正渐晕的影响。通过对距透镜不同位置处的粒子板进行测量,用灰色系统建模和无模式算法处理数据验证了该方法的有效性。这种方法可以提高距离镜头较远或覆盖范围较大的样品的测量准确度和精度。

In some case,the axial distance from the sample to the lens is long in laser particle size measurement,so vignette appears because the lens aperture is limited,which reduces the measure precision and accuracy.In order to solve the problem,the gray system theory is presented to check the optical signal data to find the vignette point.And then,the signals after the vignette point are predicted by grey-prediction model.By this way,the vignette data are amended.Experiments on a particle plate were carried out.The particle plate was placed at several positions in front of the lens.When the data were modified,a no-model algorithm was used to invert the particle size distribution.The results show the gray-prediction method is valid.The purposed means can be used to enhance the precision and accuracy in some measurement,where the axial distance from the sample to the lens is long or the covered area of the sample is large.