目的 研究LED背光源光照强度变化对视觉测量系统二维尺寸测量精度的影响。方法 通过对图像灰度与光源强度的关系进行理论推导和实验探究，得出背光源强度对图像边缘位置的影响规律。结果 随着光源强度的增强，边缘位置附近像素灰度值逐渐增大，边缘位置发生内缩，可达4.7个像素（20.03 μm）。通过自适应光强变化的动态边缘位置提取方法进行补偿，各标准轴直径测量误差减小到1个像素（4.26 μm）以内。结论 光照强度变化对影像测量系统测量精度有很大的影响，自适应光强变化的动态边缘位置提取方法能够有效补偿测量误差，提高测量精度。

The work aims to study the influence of the light intensity change of the LED backlight source on the accuracy of the two-dimensional size measurement of the visual measurement system. Through carrying out the theoretical derivation and experimental study of the relationship between image gray scale and light intensity, the influence rule of the backlight intensity on the edge position of the image was obtained. With the enhancement of the backlight intensity, the pixel gray value near the edge position gradually increased and edge position shrank up to 4.7 pixels (20.03 μm). The measurement error of the diameter of each standard axis was reduced to within 1 pixel (4.26 μm) in the method of the dynamic edge position extraction with adaptive light intensity change. The light intensity change has great influence on the measurement accuracy of the image measuring system. The method of dynamic edge position extraction with adaptive light intensity change can effectively compensate the measurement error and improve the measurement accuracy.