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Measurement of curvature radius using phase retrieval with volume speckle field

A laser beam with an ideal wavefront passes through a random amplitude mask to produce speckle fields. The speckle fields then illuminate the measured lens and are modulated by its shape to further scatter the speckle fields. The shape of the lens can be measured from the sequential intensity measurements of volume speckle field and phase retrieval based on angular-spectrum propagation technique. The curvature radius of the lens is directly derived from the shape function. In comparison with the existing measurement methods, the method proposed has a simple set-up, a strong environmental anti-interference capability and a low cost. Experimental results indicate that the proposed method is an effective approach which can be used for the measurement of radius at low cost.