Measurement of liquid lens parameters based on digital holographic microscopy

We present an experimental method to measure the curvature radius and focal length of liquid lens based on digital holographic microscopy. Considering the features of liquid lens such as non-contact, small size and non-transparent wall, a vertical optical path based on Mach-Zehnder interferometer with aberration correction capacity is used to record the hologram of sample. The phase distribution of the object wavefront carrying the liquid level information is numerically reconstructed from the recorded digital hologram and the surface contour curve is achieved by numerical computation and fitting. Then the curvature radius and focal length of the liquid lens can be obtained. In order to certify the validity of this method, a standard plano-concave lens is measured. The experimental results show that this method is an effective approach with high precision and non-contact for measuring the curvature radius and focal length of liquid lens.