Development of a traceable laser-based displacement calibration system with nanometer accuracy

High precision sensors become increasingly sensitive due to the use of advanced measuring principles and construction techniques. Traceable accuracy though can only be achieved via calibration. Based on a Fabry-Perot interferometer we have developed a calibration set-up for high precision displacement sensors that allows calibrations over a range of 300 µm with an uncertainty of about 0.5 nm. The resolution is smaller than 0.1 nm. The resonance frequency of the Fabry-Perot cavity is tracked by a slave laser. Its frequency is measured against a standard laser. By using the well known relation between the resonance frequency and the displacement of the cavity mirror the frequency data can be compared with the readout of the sensor which is connected to the moving mirror. By locking the slave laser to successive resonances of the cavity the calibration range is not limited by the tuning range of the laser.