Study on real-time compensation method for laser drift in 2D displacement measurement

Laser drift is the major factor that affects the accuracy of the propagating direction of a laser beam, and causes serious errors in 2D displacement measurement. In order to eliminate the influence of laser drift in the 2D displacement measurement system, a method of difference compensation using double laser beams is presented. Firstly, the error model for parallel drift and angular drift of light source is established based on the principle of optical structure in the displacement measurement system. Secondly, the laser drift is measured by the reference light path which is set up using beam splitter and position detector, and then it can be converted by drift error model to compensate the displacement measurement. Theoretical analysis shows that this compensation method can totally eliminate the influence of laser drift on measurement results. On this basis, the influence of structural parameter errors of actual light path on compensation results is analyzed and it provides the basis for the selection of structure parameters in the optics measurement system. The experimental results show that using the double laser beams difference compensation method, the X-axis drift reduction and Y-axis drift reduction are respectively 55.1% and 73.3% in 8 hours.