Optical interference dilatometer

Abstract

The shadow moiré technique, which is a straightforward method for contactless non-destructive metrological measurements associated with digital image processing, was used to erect a micro-movement measurement system and to design a dilatometer. By adjusting the angle of inclination of the reference grating and the angle of incident light, the sensitivity of the measurement system could be controlled. A piezoelectric material with nanometer precision was used to calibrate the measurement system. The moiré interference fringes grabbed by a CCD camera were obtained and then input into the computer, in which the digital image processing technique was employed to improve the resolution of the fringes dramatically. The results revealed that one could measure the micro-movement accurately with a slight error of about 4% using the present set-up. A dilatometer equipped with the above-mentioned measurement system was established. By comparing the thermal expansion of the specimen with the reference material, the thermal expansion coefficient of the specimen can be determined precisely, which agrees well with the literature values.