Optical systems to evaluate volume of medical samples in opaque test tubes

Measuring volume in medical samples without removing the cap of the tube is an important first step in highly automated biomedical laboratories. The variations of liquid properties, tube material, and number as well as location of labels attached to the outside of the test tube are the key points that prevent use of most traditional methods. Research into optical level detection was conducted to resolve the above issues. The research focuses on the optical detection of liquid level and volume of medical samples in the test tubes that are covered by an unknown number of labels. It has been carried out at the Precision Design Laboratory in the Department of Mechanical Engineering at University of Utah since 2006. The project is funded by the ARUP Institute for Clinical and Experimental Pathology® (ARUP). This research mainly investigates optical methods that detect the liquid level through the side of the test tube. By analyzing the change of power of transmitted light, which passes through the sample, the location of the interface between air and liquid inside the test tube is determined. To study the effect of loss of light through sample tubes, the propagation process is modeled and simulated through a ray tracing method. Experiments were conducted to verify the modeling and simulation.