A U.S. Patent Application for an “Apparatus for Detecting pH and Dissolved Oxygen” was published by Scientific Industries  on August 15th, 2019 . The present invention is a cell culture monitoring system that may include a device having collimating and filtering components to elicit and detect fluorescence from a substrate located within a reaction vessel. The device may be used to detect changes in pH and dissolved oxygen levels in a liquid contained in the reaction vessel due to growth of living cells. Excitation light beams can be generated and collimated by a beam combiner and directed into the reaction vessel so as to be incident upon the substrate to cause the substrate to fluoresce. Learn More