High-speed focal-distance-modulated fiber-coupled confocal sensor for coordinate measuring systems.

This article presents a new robust, precise, high-frequency focal-distance-modulated confocal point sensor for probing in coordinate measuring systems (CMSs). While maintaining the known advantages of the confocal measurement principle, the sensor represents an innovative combination of a fiber-coupled confocal illumination and detection with a tuneable, acoustically driven gradient-index fluid lens for modulation of the focus distance and a novel signal processing utilizing a lock-in amplifier. The new arrangement is able to achieve an approximately linear characteristic curve for the optimized feedback control of the CMS in scanning sample mode. This article emphasizes the optical application and the signal processing of the setup.