High bandwidth, dynamically rigid metrology system for the measurement

Abstract

A high bandwidth, dynamically rigid metrology system for providing real time control of an optical steering element includes a pair of stabilized laser beam directors (SLBD), a reference subsystem, a tool sensor subsystem, and at least one processor. Each SLBD includes a base, a beam pointing and stabilization apparatus mechanically coupled to the base, three reference beam lasers and a stabilized beam laser attached to the base, and a metric structure which is mechanically coupled to the SLBD providing a locally rigid SLBD coordinate system. Each beam pointing and stabilization apparatus includes an optical steering element and an axis tilt detector. The optical steering element is optically coupled to the stabilized beam laser and steers the stabilized beam laser in response to an input signal. The optical steering element provides error signals associated with a position and an orientation of the optical steering element relative to the locally rigid SLBD coordinate system. The optical steering element further includes a rotational axis. The axis tilt detector provides signals indicating an angle of tilt and a direction of the rotational axis relative to an initial position of the rotational axis. The reference subsystem includes three reference detectors fixedly positioned relative to a workpiece providing a locally rigid workpiece coordinate system. The three referenced detectors are respectively in optical communication with the three reference beam lasers of each of the SLBDs. The reference detectors generate reference detector output signals in response to the reference beam lasers. The tool sensor subsystem includes at least one tool sensor detector positioned on a tool and in optical communication with the stabilized beam laser. The at least one tool sensor detector generates tool sensor detector output signals in response to the stabilized beam laser. The at least one processor receives and performs coordinate transforms on the referenced detector output signals and the tool sensor detector output signals to track a position of the tool relative to the locally rigid workpiece coordinate system. The at least one processor additionally receives and processes the angle of tilt and direction signals from the axis tilt detector and the error signals from the optical steering element to generate the input signal thereby providing real time control of the optical steering elements.