US Patent 7540096 Vacuum-actuated spherometer

A spherometer for measuring at least one physical parameter of the workpiece includes at least on fluid-actuated linearly extensible probe member having an output indicative of an amount of linear travel and a chamber housing the linearly extensible probe member. The chamber has an aperture for supporting a workpiece and a vacuum line is coupled to the chamber for creating a vacuum. The probe member is activated as a result of the vacuum in the chamber, causing it to extend linearly toward the workpiece until touching it. The linear extension of the probe may be used as a measurement of distance. The distance measured to a workpiece may be compared to a standard to determine a physical parameter of the workpiece.