An interferometer with continuously variable bandpass filter

The paper focuses on a new approach to variable wavelength interferometry. The presented optical configuration includes a continuously variable bandpass filter instead of a continuously tuned light source. In the demonstrated solution sequential recording of images is not necessary. The fringe field analysis utilizes a single image. The solution is suitable for both transmitted and reflected-light modes. The filter can be mounted in different parts of the optical system. In this paper, we demonstrate initial results of measurements of the spectral characteristic of a retarder when the filter is placed in the plane of the field stop in the Kӧhler illumination system. The fast analysis of the single interferogram constitutes the key element of novelty of the system and enables the instrument to be used in industrial environment.