Abstract: A method and apparatus is disclosed for determining physical characteristics, such as defects, in the outer surface of an elongate object, wherein the object to be inspected passes through an aperture of a mirror surface which is a conical surface of revolution. Light directed onto the mirror surface in an axial direction is reflected by the object surface, imaged, and analyzed to determine a physical characteristic of the object surface.

Abstract: A method of determining physical characteristics of a surface. Light or other electromagnetic radiation is directed onto a first portion of a surface and the reflected radiation is received such as by a photodiode. The radiation is also directed onto at least two further portions of the surface and located on either side of and proximate to the first portion. The radiation reflected by the further portions is also received. The radiation reflected from the first portion is compared with the radiation reflected from the two further portions. The radiation and comparison steps are repeated and the comparisons are used to determine a physical characteristic of the surface, such as the presence of one or more flaws. In another embodiment, light or other electromagnetic radiation is used to determine object dimension, such as bore dimension.