A new method for measuring the radius of curvature (ROC) of an optical surface having a large radius is proposed. The method combines a Fizeau interferometer and a specially designed zoom lens to form a compact and convenient test setup, so that measurement of the curvatures for both concave and convex surfaces having a large ROC can be done in a simple and quick way. The design of the zoom lenses for this application, principle of the measurement, and calibration of the zoom lenses are discussed. By means of the proposed method, radii of 1.5 m to infinity, concave or convex surfaces, can be measured in compact setups efficiently. The accuracy of the measurements can reach up to 0.04percent for a surface having a radius of 10 m.
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