Improving measurement accuracy of laser triangulation sensor via integrating a diffraction grating

In this paper, a laser triangulation sensor (LTS) with improved measurement accuracy via integrating a diffraction grating was proved. Compared to conventional LTS that only has the information of one light spot, the diffraction grating generates several diffraction light spots on CMOS image sensor. This enables to obtain multiple results of the object displacement simultaneously during one sampling period. Thus, it is achievable to obtain a higher measurement accuracy by averaging operation, due to the averaging-error effect. The operating principle of the proposed method is explained in detail, and a prototype LTS is developed. Contrastive experiments are performed to evaluate the nonlinearity and repeatability of the developed LTS, which are generally combined to present the measurement accuracy of LTS. In the full-scale measurement range of 20 mm (F.S. = 20 mm), the results show that the measurement nonlinearity and repeatability of the developed LTS with diffraction grating are 0.113% of F.S. and 0.89 μm respectively, which are significantly improved compared to that without diffraction grating.