Jamin-Lebedeff polarizing interference microscopy is a classical method for determining the refractive index and thickness of transparent tissues. In cytology this method can be used as an easy way to determine the phase difference and therefore the dry mass per area of cells, microorganisms, etc. It offers the advantage of acquiring quantitative phase information in one image only. However this method as well as the microscopy equipment is rather old and also very rare nowadays. We decided to bring the Jamin-Lebedeff microscope back to life using a smartphone for capturing images. The aim is to create an Android app which will allow the user to simply acquire the phase map of the sample. Because of the short time stability of the microscope settings, firstly a calibration image is taken to define the relationship between three colour channels and the optical path difference (proportional to phase difference). We used an immersed fibre of defined thickness and refractive index prepared with optical path difference in the range from zero to three times the wavelength, which is fairly enough for all living cells. Some issues arose due to the fact that the microscope is old and not produced any more. Parts, which were missing or didn’t fit the needs were replaced or adjusted with self-made 3D-printed components.