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In recent years, remarkable progress has been made in high precision machining for the production of metallic concave mirrors. However, to improve efficiency and precision in the cutting process, it is desirable to design a measurement device built into the cutting machinery and to be easy to handle. In this paper we propose a promising and practical innovation in measurement based on zone-plate interferometry. This method involves the operation of changing the curvature radius of the diffracted wave fronts by moving the zone-plate along the optical axis, and it has the merit of easy application to the measurement both spherical and aspherical mirror profiles.