Abstract
A “roller” extensometer was calibrated using a Michelson-type interferometer with a He-Ne laser source. This calibration system was capable of detecting relative displacements smaller than 0.016μm. The super-invar rod of the extensometer was displaced longitudinally about 2-7μm with a heating element consisting of a wire-wound bar of glass and a reflecting aluminum plate. The resultant displacement was detected by reading the fringe displacement records which had been converted photo-electrically by two differential photodiodes . As a result of this calibration, it was found that the sensitivity of the “roller” extensometer, which had been calculated from the radius of a roller and the optical length, was about 3560% of the true value for the range of the relative displacement amplitude of ±1-3μm.
