New optical system for reducing the interference fringe density in laser interferometric measurement of tooth flank form of a gear

In interferometric measurement, it is important to obtain a clear interfere nce fringe pattern. A high density of fringes in interferometric measuremen ts of involute gear tooth induces noises in the measuring signal and makes analysis difficult. In this paper, we propose a new optical system to obtai n an interference fringe pattern of low density. A spherical concave lens i s added in the optical path of the reference beam to deform the curved figu re of phase of the reference beam over a charge-coupled device image sensor . By selecting a suitable focal length of the inserted concave lens, the ph ase difference between the reference beam and the object beam becomes fairl y small over the CCD image sensor and the fringe density of the interferenc e fringe pattern decreases. The effect of this new optical system is invest igated.