Two high-speed, dimensional measurement systems have been developed. Both have several advantages over conventional measurement systems. Both have been designed around the use of line gratings. The first system measures and controls the flatness of opaque objects to a resolution of 100 microinches. The method is fast, non-contacting, self-calibrating, can be used in a limited access area, and can be applied to moving surfaces. The second system is used to measure and control the width of continuous opaque objects such as tapes. The method is noncontacting, minimizing frictional wear. One thousand measurements per second, at a resolution of 100 microinches, can be made.