Optical measuring system

Abstract

A non-contacting optical probe incorporates an optical system designed to measure distances between various surfaces which may be internal or external such as exists in molds and the like. A collimated light beam is passed off-center through a first lens and focused to a first point on a first surface coplanar with the focal plane of the lens. When the distance between the first surface and the optical probe carrying the collimated beam changes so that a second surface is presented, this second surface is no longer in the focal plane with the result that a laterally displaced image of the point of interception of the collimated beam with the point of the intersection of the optical axis of the system occurs. This lateral displacement is imaged back through the optical system to a sensing surface. The primary focusing lens is then physically shifted along its optical axis to bring the focal plane into coplanar relationship with the second surface, the amount of lens movement being readily determined when the laterally displaced image point on the sensor surface is brought into coincidence with the center optical axis of the lens system on the sensor surface. The distance through which the lens is physically moved then corresponds precisely to the distance between the first and second surfaces.