US Patent 7971365 Apparatus and method of measuring workpieces

A method and apparatus for measuring a surface using a surface sensing device mounted on a scanning head on a member of a coordinate positioning apparatus. The coordinate positioning apparatus may be operated to produce relative movement between the scanning head and the surface profile and the scanning head includes a drive for producing rotational movement of the surface sensing probe about one or more axis. The coordinate positioning apparatus is driven to provide relative movement between the member and the surface profile in a circular path and the probe head is driven to move the surface sensing device about said one or more axes, such that the surface sensing device maintains a nominally constant lead angle. The motion of the coordinate positioning apparatus and probe head is synchronous.