Detection and Compensation of Periodic Vibrations on a Nanometer Scale using High-sensitivity Accelerometers in Digital Holography Sensors

Digital holographic (DH) sensors enable the measurement of optical or technical surfaces with sub-micron precision. Recent developments in embedded computing and optical setups have led to smaller sensor sizes. As a result, modern DH sensors can be deployed on various multi-axis carrier systems, such as machine tools, coordinate measuring machines (CMM) or even industrial robots. However, these handling systems are prone to mechanical vibrations, which can cause errors in the holographic measurements. The need for a solution to detect and compensate such vibrations arises. In this article, we propose an approach to compensate the vibrations in DH sensor systems using the implementation of a Bandwidth Limited Fourier Linear Combiner (BMFLC) and an active interferometer. We will show that displacement information between the measurement object and the sensor can be obtained in nanometer scale by utilizing a high precision accelerometer (IMU) in combination with a BMFLC. This can be exploited to compensate variations in optical pathlength affecting the underlying interferometer of the holography sensor. Compared to the uncompensated system, the presented implementation reduces the displacement amplitude of a periodic vibration of 48 nm to 16 nm at a frequency below 100 Hz. This is within the typical range of frequencies the sensors are exposed to.