Automatic Calibration Method on PCB Inspecting System

The paper introduces automatic calibration method on AOI for PCB inspecting. Three optical points are needed at least. And the centre of them are located by least squares solution, which are used for calculating transformation coefficient between image coordinate and physic coordinate. Computer adjusts distance between CCD lens and PCB according to transformation coefficient continuously till realizing function of calibration. The experimental results prove that the method guarantees the precision of calibration and demonstrates practical usefulness.