Automatic interferometer with digital readout for refractometric analysis

The paper describes an interference refractometer for liquids and gases which operates automatically and reads out in digital or analog form. A compensating technique using white light is used for measurement. Zero adjustment is achieved by rotating the compensator and capturing the zero-order white light fringe by photoelectric means. Measurement of the path difference compensated by the compensator is based on electronic interpolation and counting of interference fringes by optointerferometric means, a time division multiplex technique with pulse amplitude modulation being used to obtain the electrical fringe signals.