A New Method for Measuring Multilayer Thickness Using a Chromatic Confocal Sensor

Abstract Multilayer transparent plates play a crucial role in industrial fields, such as optical lenses, electrodes, and solar panels, because of their superior optical and electrical properties. The thickness and uniformity of such plates are decisive for the quality of the final product. However, traditional contact measurement methods are inadequate in accuracy and pose the risk of damaging the plates, making nondestructive measurement of multilayer transparent plate thickness rather challenging. A new measurement technology is urgently needed. This study proposes a new method for the thickness measurement of multilayer transparent plates based on chromatic confocal sensor technology. First, we investigated the dispersive behavior of light in various media layers and derived theoretical measurement models for single-layer and multilayer transparent plate thicknesses. Subsequently, we designed and constructed a measurement system using a C-series chromatic confocal sensor and optical instruments and prepared a five-layer transparent sample consisting of quartz and air layers to confirm the feasibility of the method. The results of the experiment show that the proposed method can accurately measure the thickness of the five-layer sample with a maximum absolute error within 13 µm and a maximum relative error of 4.27%, thus proving its validity, precision, and stability. The results further indicate the high practicality and reliability of this technology in production environments, theoretically enabling the simultaneous measurement of up to 18 layers of the plate and offering broad application prospects in the industry.