Method and apparatus for determining the concentration of optically-active materials in a fluid

US5457535A · kind A · utility

Assignee

• Siemens Aktiengesellschaft · DE

Inventors

• Gerhard Schmidtke · Glückstadt, DE
• Wolfgang Riedel · Neuenbürg, DE
• Helmut Wolf · Holzkirchen, DE

Key dates

• Filing date: Mar 28, 1994
• Grant date: Oct 10, 1995
• Expiry date: Mar 28, 2014

Classification

• Technology area (CPC G): Physics
• CPC primary: G01N21/21
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

In a method and apparatus for determining the concentration of optically-active substances in a fluid, such as glucose in the body fluids of a patient, two light sources are used to produce respective polarized light beams which pass through the substance to be analyzed and are incident on a detector. The second beam has a fixed polarization direction relative to the first beam. The light sources are alternatingly switched on and off at a known-frequency. A dispersing element is disposed in the path of each beam. A comparative signal is produced from the beams exiting the substance and incident on the detector. Due to the presence of the dispersive element in the path of each beam, it is possible to spectrally resolve the components of the comparative signals, so that the optical polarization contributed to the comparative signal by each substance in the fluid can be identified, and thus the concentration of a selected optically-active substance, even in the presence of multiple optically-active substances in the fluid, can be accurately identified.