As a specialized manufacturer of laser particle size analyzer, Bettersize has made good progress in developing new technologies and obtained dozens of patents over the years. DLOS (dual lens optical system) is a typical example of the advanced technologies developed by Bettersize. As shown in the diagram below, DLOS places the same Fourier lens symmetrically on both sides of the sample cell for converging scattered light. The lens on the left side is used to receive the forward scattered light; the lens on the right side has two functions: to receive the back scattered light and to turn divergent laser beam into parallel light as an aligning lens. A set of photo-detector arrays is respectively placed on the focal planes of the two lenses, which receives the scattered light after converging by the lenses. DLOS doubled the scattered light detection area, improved the test range, and enhanced the test accuracy, particularly for ultrafine particles. Compared with the multi-beam optical system, DLOS consumed less energy and provided higher reliability. DLOS has been successfully and widely used by all models of Bettersizer series.