Method for inspecting the curvature of a profile, such an edge of a

Abstract

The curvature of an edge such as the trailing edge of a turbine blade having a specular reflection surface is inspected by illuminating the surface area to be measured with a laser beam and sensing the reflected laser light. The laser beam intensity across the cross-section of the laser beam is varied by a radiation intensity matrix located between the laser beam generator and the edge to be sensed or measured, whereby local radiation intensity variations are provided in the form of illuminating laser beam segments (A, B, C, . . . ) having different intensities. The beam reflected segments (A', B', C', . . . ) have a reflection angle that is equal to the incidence angle of the respective illuminating laser beam segments (A, B, C, . . . ). This fact is used for the correlation (A, A'; B, B'; C, C', . . . ). The reflected beam segments (A', B', C', . . . ) are scanned in a line-by-line fashion whereby the radiation intensity values varying along the curvature are measured. The measured values are then processed in a central processing unit for producing the curvature profile. The method can be used especially for measuring sharp edges, such as knife edges, cutting tool edges, or turbine blade edges and the like. The illumination is direct without any optical components between the matrix and the surface to be inspected.