Asymmetric design for improving the accuracy of laser triangulation sensor

The article demonstrates a laser triangulation sensor (LTS) that enhances measurement accuracy by adjusting the location of the primary optical axis of the lens on the CMOS image sensor. The objective of this research is to fully exploit the performance potential of the LTS while maintaining current hardware conditions and fulfilling the preset measurement range requirements. First, the measurement model for the LTS via Scheimpflug principle is established, and the feasibility of its asymmetric structure is analyzed using the sensitivity curve. Then, prototypes of LTS symmetric and asymmetric structures have been developed. A customized lens tube is introduced to flexibly adjust the relative position between the lens and the CMOS image sensor, enabling accurate control over the landing position of the primary optical axis of the lens. Additionally, a detailed two-step calibration strategy is elaborated to ensure that the actual structural parameters are closely aligned with the theoretical values. Finally, repeated and contrastive experiments are conducted to systematically evaluate the performance of the established LTS. The experimental results indicate that, in comparison to the symmetrical structure of LTS, the maximum absolute error and nonlinearity of the asymmetrical structure are reduced by over 70 % and 50 % respectively, which clearly demonstrate the significant effectiveness of the proposed structure in enhancing the nonlinear characteristics of LTS.