Theoretical and experimental study on two-stage-imaging microscopy using ellipsometric contrast for real-time...

A two-stage-imaging ellipsometric-contrast microscope (TIEM) has been developed to measure the distribution of film thickness over a wide area of molecularly thin liquid films with a high lateral resolution, wide field of view, high thickness resolution, and high-speed. Moreover, this ellipsometric microscope enables us to achieve simultaneous measurements with other measurement apparatuses. We present the principle used to parallelize an object image to an imaging sensor and to reduce the incident angle entering the imaging sensor. In addition, we discuss the characteristic shape deformation of the object image due to oblique observation. The performance of the actual setup for TIEM was experimentally studied. A lateral resolution of about 1 μm was obtained by measuring the modulation transfer function of the TIEM. We also found that the shape deformation approximately agreed with that from theory. Furthermore, for molecularly thin films, we confirmed linearity between the film thickness and the light intensity measured with TIEM, which enables us to quantify the thickness of the films. TIEM can open up a new field of real-time imaging of thin films such as visualization of a liquid lubricant film under shear.