Abstract: A strain-isolated mirror is made from a substrate having first and second body portions. First and second connecting portions extend across a gap between the first body portion and the second body portion. A first flexural hinge on the first second connecting portion couples the second connecting portion to the first body portion.

Abstract: A strain-isolated mirror is made from a substrate having first and second body portions. First and second connecting portions extend across a gap between the first body portion and the second body portion. A first flexural hinge on the first second connecting portion couples the second connecting portion to the first body portion.

Abstract: At least one dimensional characteristic of a workpiece is measured, in situ, while at least one surface of the workpiece is subjected to a finishing operation. The measurements are obtained using an interferometer that generates interfering wavefronts reflected from the front and rear surfaces of the workpiece. Variations in the optical thickness of the workpiece can be determined from the resulting interferogram. The resulting optical thickness data can be used directly and/or combined with other pre-acquired data about the workpiece to obtain information concerning a desired dimensional characteristic of the workpiece. This dimensional characteristic may be transmitted wavefront error, work surface smoothness, and/or work surface profile. These measurements then can be used to terminate the finishing process at an optimal time and/or to control the operation of the surface-finishing machine.