A borehole apparatus detects the presence of gas within a formation fluid sample. A light source transmits light rays to an interface between the fluid sample and the flow line. The interface reflects the light rays toward a detector array. The detector array detects light rays having angles of incidences...http://www.google.de/patents/US5201220?utm_source=gb-gplus-sharePatent US5201220 - Apparatus and method for detecting the presence of gas in a borehole flow stream
