What are the advantages of a flat top laser beam?

The flat top laser beam utilized in the optical particle counter provides a laser beam with uniformly distributed light intensity, ensuring a homogeneous illumination of the particles passing through the laser beam. The light extinction method is suitable for particles whose particle size is large than 1μm; for smaller particles smaller than 1μm, laser scattering is prioritized. The light intensity of the “wings” of the Gaussian laser beam is relatively low. Therefore, the corresponding scattered light signal probably cannot be identified when a small particle is illuminated in this position due to insufficient light intensity. The problem can be solved by using a flat top laser beam, in which the particles with the same particle size on the cross section of the laser beam are identically irradiated, providing constant pulse signals, improving counting accuracy, and expanding measurement range.

Besides, pulse signals are different when two identical particles are illuminated at different positions on the cross section of a pure Gaussian laser beam, leading to errors in particle size analysis. Compared to Gaussian beams, the application of flat top beams offers more accurate and predictable results.

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