Interferometric method displacement instrument - measures temperature coefficient of expansion, and young's or poisson's modulus of materials

摘要

The instrument consists of a Michelson interferometer (10) made up of a light source (12), a separating screen (14), a first mirror (16), a second mirror (18) and a device for viewing and counting interference fringes (20). Mirror (16) is fixed but mirror (18) is mounted on an auxiliary device (22) which may slide along a table (24) although staying in-line with the light source (12). The position of the auxiliary device (22) is such that point (M) is at a distance (f) from the plane of reference of the device (22). The distance (f) is measured. As the position of point (M) changes, distance (f) is maintained constant and mirror (18) will then be kept at a constant distance from the point being measured. The interferometer (10) measures the displacement of mirror (18) to give the longitudinal displacement of point (M).