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

Abstract

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.

Effect of a Misidentified Centre of a Type ASG Material Measure on the Determined Topographic Spatial Resolution of an Optical Point Sensor

“…The setup consisted of a fibre-coupled confocal sensor firstly described in [67] and in its latest design, as it was applied for the investigations shown within this paper, in [68]. A thorough description of the sensor, including the theory of the signal formation based on general works on fibre-coupled confocal sensors of Gu et al [69], may be found in [70].…”

Variable optical elements for fast focus control

“…One of the challenges associated with dimensional metrology is to generate highly accurate 3D relative motions between sensors and measured surfaces with sub-µm resolutions. An ultra-high-speed varifocal lens has been implemented to develop a highly accurate confocal point sensor for nano-coordinate measuring systems (CMS) 102 . Combined with a signal processing method, light-information from the fast focus modulation has been used in the confocal point sensor to significantly improve accuracy and to reduce measurement uncertainty and the probing time.…”

Evaluation und Korrektur thermischer Driften eines hochfrequent fokusabstandsmodulierten, fasergekoppelten konfokalen Punktsensors / Evaluation and correction of thermal drifts using a high-speed focal-distance-modulated fibre-coupled confocal sensor

“…Der optische Aufbau des Sensors wurde detailliert in [8] vorgestellt und ist in Abbildung 1 skizziert.…”

“…Weiterhin werden akustisch getriebene, hochfrequent modulierbare Gradientenoptiken in Mikroskopieanwendungen [10] und konfokalen Systemen genutzt [3]. Die Kombination eines fasergekoppelten, konfokalen Punktsensors mit einer solchen Gradientenoptik zur hochfrequenten Modulation der Fokusposition unter Beibehaltung aller bekannten Vorteile der Konfokaltechnik und die Signalverarbeitung, mit welcher eine annähernd lineare Kennlinie erzeugt wird, wurde in [8] vorgestellt und wird in Kapitel 2 nochmals kurz skizziert. Außerdem ließ sich durch Quotientenbildung bei der Signalverarbeitung eine von der Reflektivität der Werkstückoberfläche und von der Verkippung derselben weitestgehend unabhängige Kennlinie erreichen [4,6].…”