Non-contact measurement of bore hole geometries 28.09.2009 Checking the geometry of bore holes is a widespread industrial problem. There are already solutions for which conventional, confocal sensor technology is typically used. However, due to the large diameter of these sensors (approx. 20mm and larger), they are not able to measure in very small bore holes. The new confocal sensor from Micro-Epsilon is therefore completely unique. With its miniaturised confocal sensor, which has a diameter of just 4mm in the standard version, an inspection of very narrow bore holes can be carried out for the first time. The product is often referred to as an “optical bore hole sensor” and functions with a special version of the standard optoNCDT 2402/90 sensor, with a diameter of only 3.5mm. The sensor can therefore be used for bore holes with diameters from 4mm upwards. The sensor is rotated by an electric motor and can measure the diameter, roundness, concentricity, tapering and the straightness of bore holes. A complex, integrated precision ball bearing system provides the necessary rotation stability. Development problems centred around the transmission of the light beam to a rotating sensor lens. Like the linear standard systems, the confocal technology is suitable for all surfaces where the reflected light beam from the lens is reflected back into the sensor. Therefore, measuring tapered bore holes is only possible to a certain degree. Due to the installation length, the sensor can measure bore holes up to 50mm in depth. In doing so, the sensor lance is guided into the bore hole using a linear unit provided by the customer. If the sensor becomes damaged, the sensor lance can be replaced quickly. The system is used in industry for quality inspection of bore holes in production lines or in test laboratories.