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As an association of Legendre polynomials. Mie theory is to describe the rigorous theory of light scattering particles of any size in the classic sense. However, the large particles (), the numerical calculation of Mie scattering formula is very complicated. People usually think that this case, the scattering phenomenon can be described with the more common and simple diffraction formula. When the scattering particle to the observation point distance is infinity, the diffraction formula can be simplified for Fraunhoff diffraction formula: If you only consider the scattered light intensity distribution in the conditions under Fraunhoff theory and Mie theory the difference is very small indeed. However, laser particle size analyzer, the photodetector receives the light energy (intensity detector receiving surface integral). It depends on the specific indices and parameters of laser stage lighting.
Receiver area increases rapidly as the receive angle increases, this time in the vicinity of 14 ° (a particle refractive index of 1.54, the position corresponding to the peak of 1μm particles scattering the light distribution), the light can ambitious predictions theory Fraunhoff. Therefore, if the acceptance angle of the laser particle size analyzer close to or greater than 14 °, or the minimum laser particle size analyzer measurement is less than or equal to 1μm, the diffraction theory obvious error (1μm near the number of particles). The subject laser particle size analyzer using rigorous Mie theory as a theoretical basis. Laser particle size analyzer, test speed, wide measuring range, a wide range of applications, can be used for the measurement of spray, powder or suspension. The occasion and location where the customer will use laser stage lighting .
Moreover, laser particle size analyzer in the measurement process does not destroy the sample field, is a non-contact measurement, online measurement. The principle of laser particle size analyzer. General instrument of measurement units, injection systems, computer and printer, as shown in Figure 2.2 shown below: Figure 2.2 Schematic diagram of the instrument. Issued from the He-Ne laser (1) the wavelength of the laser beam 0.6328μm, after beam expander (2) convergence in the pinhole (3), pinhole filter out all high-level scattered light, so that only the low spatial frequency laser pass. Then the laser beam divergence of the beam. The beam encounters the lens (5) after focusing. Reflection prism (6) the turning point of the optical system of the optical axis 90 °, namely, to make it into a vertical spread by horizontal transmission. The infrared light band can form a larger spot around the green light of cheap led lights.
Pool no particles in the sample, the beam will be focused on the center of the ring photodetector (9), and through the center holes to shine on the center of the detector (10). When the particulate samples in the sample pool, convergent beam will be part of the particle scattering to the ring detector, the detector unit, as well as bighorn detector. Based particles of the sample pool, the center of the detector receives light energy E0 known as shading. The higher the sample concentration, shading ratio. I = 1,2, ..., n; called the scattering of light distribution, which contains the test particle size distribution information. Light signal by the photodetector is converted into the corresponding current signal, sent to data acquisition card. The card will signal amplification, and then sent to the computer after A / D converter. If the large spot formed by the infrared light band has some influence on the green laser beam light emitted by laser stage lighting.
Optical structure based on light scattering theory and instrumentation, computer prior to calculate the scattering light distribution of various diameters in the range of instruments to measure particle corresponding to the collection composed of a light matrix M, namely: matrix each column represents a grain The diameter of the scope of a unit weight of particles scattering light distribution. Thus: where w1, w2, ..., wn representative particle weight distribution. According to the above equation, as long as the known scattering light distribution s1, s2, ... sn, through appropriate means of numerical calculation can calculate the corresponding particle size distribution. Laser alignment technology. Laser technology on the product of the combination of laser, light sensors and computer testing techniques, efficient, stable and fast. The infrared optical filter of laser stage lighting is needed for the customer.