Calibration of Displacement Sensors with High-Precision and Large Measurement Range Using Temporal Speckle Pattern Interferometry

In the present study, a real-time calibration method for micro displacement sensors is introduced, and a calibration system is developed. SPCM, the sequence pulse counting method previously proposed by us, is capable of automatically determining both the larger range displacement and the performance of a sensor, such as the nonlinear error and the displacement sensitivity within a quarter of the light source wavelength. The new calibration system consists of a programmable motor driven platform, an out-of-plane sensitive electronic speckle pattern interferometry (ESPI), and a sequence image acquisition system. The platform is used to provide displacement changes of a moving component and its displacement is measured by the ESPI and calibrated sensor synchronously. The calibration accuracy of the proposed method is in the submicrometer level and the displacement range can be from sub-micrometer to millimeters depending on the storage capacity of the computer and the correlation property of the interferometer. Three capacitance-type displacement sensors have been calibrated successfully, whose displacement ranges are –300μm to 300μm, –30μm to 30μm, and –3μm to 3μm, respectively.