Vibration-insensitive low coherence interferometer (LCI) for the measurement of technical surfaces

Abstract

Abstract For the evaluation of operationally stressed surfaces containing microstructures, robot guided measurement systems need to be designed, that are able to automatically measure the integrity of these microstructures in a production related environment. Because drifts or vibrations between the robot mounted sensor and the sample surface noticeably influence measurement results, leading to usually insufficient results even large non-measured areas. The measurement system should be designed both to precisely measure the sample surface and to robustly handle the influences of the environmental vibration. In this paper, we introduce a robot guided low coherence interferometer (LCI) system, that can compensate inevitable drifts and vibrations using high-speed data acquisition and a phase correction method, which can analyze and correct distorted inferoferograms using Hilbert-Transform in the frequency domain. Utilizing these methods the measurement performance of this system can be improved in comparison with the conventional LCI, to reduce non-measured areas and to reach a low measurement deviation of less than 0.1 μm. The detailed capability of the proposed methods for the identification and the compensation of environmental vibration is shown based on experimental data.