Optical method for accurate force measurement: Dynamic response evaluation of an impact hammer

Impact response of an impact hammer is evaluated by means of an optical method. In the method, an object levitated with sufficiently small friction using a pneumatic linear bearing is collided with the impact hammer under test. The inertial force, that is the product of the mass and the acceleration, is measured highly accurately by means of measuring the Doppler frequency shift of the laser light beam reflected on the mass. The velocity, the position, the acceleration and the inertial force of the mass are then numerically calculated from the time-varying frequency. The output signal of a force transducer embedded in the hammer and the inertial force measured by the method are compared. The present status and the future prospects of the proposed method are discussed.