Optical inspection system employing spherical mirror

摘要

An optical system having a spherical mirror is used to collect light from the surface of a turbine blade or the like which is to be contoured. The spherical mirror is located at an equal optical distance from both the test specimen and the linear diode array so that it operates at a one-to-one magnification ratio. The linear diode array is positioned behind the spherical mirror and it receives light focused by the mirror and reflected by a beam splitter through an opening in the center of the mirror. None of the optical elements of the inspection system are located in the plane of movement of the test specimen so that even particularly long items such as a helicopter rotor blade can be contoured. Indentical upper and lower optical systems allows both surfaces of the test specimen to be contoured simultaneously and each system is independently operable and oriented to prevent optical interference. An automatic gain control is provided to adjust the optical modulator so that the effective intensity of the spot presented to the diode array is maintained within predetermined limits.