OPTOACOUSTIC CELL FOR IDENTIFYING LIQUIDS

摘要

An optoacoustic cell is a device which measures the amount of light energy absorbed in a medium through the acoustic pressure resulting from the absorption. The cell normally consists of a container with a pressure measuring device, In particular the two functions may be combined if the container, a piezoceramic cylinder, is itself a pressure measuring device. The medium under study is contained in the cell by an optical window of windows. In the present example two windows seal the ends of the cylinder which contains a fluid to be identified. Commonly, one of two types of light beam traverses the cylinder axis of the optoacoustlc cell: either (1) a periodically modulated light beam of continuous, constant intensity or (2) a short duration light pulse. In this application we employ the second type. The advancement in the art consists in the recognition that the signal produced by the pressure measuring device depends both on the type of piezoceramic cylinder used and the exact nature of the contained fluid. The dependency is complicated and when the signal of the pressure measuring device is viewed against a time axis a pattern results, commonly called a fingerprint, which is specific to the particular fluid contained in the optoacoustlc cell. The reason for this fingerprinting ability may be explained on the basis of the natural oscillation modes in the cylinder. The utility of the invention lies in its providing a new means for identification of fluids. Fluid mixtures could also be identified.