Enhancing the Accuracy and Range of Cantilever-Based Measurements in Optical Beam Deflection Systems

Accurate characterization of surfaces using cantilever-based optical beam deflection (OBD) systems is crucial for obtaining the sample’s “true” topography and its corresponding material properties. Conventional OBD systems, such as those used in scanning probe microscopy (SPM), typically account for only the rotational displacement of the cantilever, while neglecting its translational displacement relative to the quadrant photodiode (QPD). This can possibly result in considerable measurement errors, particularly in applications using long cantilevers or when the sample has significant topographic variations. This article addresses this limitation by introducing a correction factor, based only on kinematic parameters, that accounts for both the translational and rotational components of the cantilever’s displacement. The proposed solution requires no information about the forces involved or the material properties of the cantilever or the test sample, and is suitable for quasi-static applications. Experimental validation with macro-scale cantilevers demonstrates improved measurement accuracy by mitigating the errors arising from factors such as the cantilever’s preload (setpoint), the cantilever’s and laser beam’s inclination, and the distance between the cantilever and the QPD. This framework not only helps to enhance the accuracy and range of cantilever-based measurement systems through the proposed correction factor but also provides practical guidance for selecting the system’s parameters.