The LDA comprises three distinct parts:
■ an optical emission device, comprising a laser and a system of division of the beam (beam splitter);
■ a receiving device comprising an optical system as well as a photomultiplier;
■ a system for processing signals received by the photomultiplier.
220.127.116.11 Optical emission device
This device consists of a laser beam which is split into two parallel beams by a prism, then the two beams pass through a lens that makes them converge in its focus. The point of intersection of the two beams is the measurement volume. In the case of the reference beam LDA, a neutral density filter is interposed in the path of one of the beams in order to reduce its intensity.