An air-bearing displacement sensor with a micro-ball stylus for profile measurement of 3D micro-structured surfaces

Micro-structured surfaces such as micro-aspheric lenses/lens arrays and micro-gears are getting increasingly important in industries. A lot of micro-structured surfaces have complicated three-dimensional (3D) profiles with short pitches and large amplitudes (high-aspect-ratio). Some of them also have steep surface slopes. It is difficult, however, to use conventional measuring instruments to measure profiles of such 3D micro-structured surfaces. This paper describes a contact-type displacement sensor for profile measurement of 3D microstructured surfaces. The shaft of the sensor is levitated by air-bearings to reduce the contact force between the sensor and the measured surface. A sharp corn stylus is attached at the end of the sensor shaft. A precision glass micro-ball is glued on the top of the stylus shaft. The diameter of micro-ball is under 50 mu m. The displacement sensor is also used to measure the profile of a micro gear with a high-aspect-ratio surface profile.