Optical detector for air in fluid line the same

Abstract

Ambiguity, in readings from an optical bubble detector used with tubing, can be reduced by shaping the tubing into the shape of a prism, so that when different contents of the tubing have differing indices of refraction, there is a clear difference in the exit angle of the light beam leaving the tube. A triangular prism shape is preferred for the compressed tubing. The optical bubble detector features an optics block formed with a V-shaped recess, and a clamp block. The optics block and clamp block cooperatively press or 'sandwich' the flexible tubing into the V-shaped recess and deform it into a triangular prismatic cross-section. A generally U-shaped optical interrupter element, containing a photoemitter and a photosensor, fits into the optics block in such a manner that a light beam is directed radially into the triangular tubing section. The clamp block 'windows' the transmitted and received light from the optical interrupter, to allow only a thin channel of light to be transmitted; this minimizes optical noise during measurement. When saline is located in the tubing, the light follows a fairly straight path through the optics block and tubing. However, when air is in the tubing, the light is refracted away from the photosensor, resulting in lower intensity readings. By measuring the amount of light received at the photosensor, it can be determined whether air, or saline, is in the tubing.