Increasing demands for the monitoring of tolerances of small mechanical and optical precision components require improved measurement techniques. In this paper the basic concept and different optical designs of a confocal microoptical distance-sensor are presented. The sensors use the chromatic-confocal measurement principle which does not require a mechanical depth scan. Therefore, a chromatic-confocal point sensor can be designed without any moving parts. This fact is used to design a miniaturized sensor head with an outer diameter smaller than two millimetres. A special feature of the sensor head is its capability to measure sideways. This enables e.g. to measure surfaces in small drilling holes.
In this paper, the realization and characterization of a microoptical sensor using the chromatic confocal principle is presented. The sensor head is designed for distance gauging applications in high aspect ratio cavities with a diameter of about 2 mm. The first part of this paper focuses on the design and fabrication process of the hybrid optical benches, which combines refractive and diffractive micro optical components. Very tight tolerances of the optical path are required for the functionality of the sensor. Therefore the alignment structures and mounts between the different optical elements are produced from PMMA using deep X-ray lithography, the first step of the LIGA process.
In the second part of this paper the characterization of first prototypes using different light sources are described and results presented.
Increasing demands for controlling tolerances of small mechanical and optical components require improved measurement techniques. In particular, components with a complex geometry such as small holes or channels are difficult to access by classical tactile measurement systems. These systems are also limited in their measurement speed. Optical distance sensors do not have many of these disadvantages, but the sensor heads are normally too large to access e.g. small holes. Presented in this paper is a novel microoptical sensor concept using the chromatic confocal principle for distance gauging applications. This is used in high aspect ratio cavities with a diameter of about 2 mm. The distance resolution of the sensor is aimed to be in the sub-micrometer range.