Apparatus for determination of particle sizes and/or distributions of particle sizes comprises a light source which radiates parallel light of high coherence through a measuring zone (14) in which the particles to be measured are disposed. The light beam diffracted at the particles is imaged by an imaging device (18) onto a photo-detector (20) which is coupled to an evaluating unit (22). The imaging device (18) is provided with several different focal lengths which can be selectably brought into the beam path of the overall device. At the start of a measuring process a control device causes the distribution of particle sizes initially to be determined with the use of the longest focal length and employment of evaluation mathematics valid for this focal length. After the evaluating unit (22) has ascertained that particle size fraction into which the largest measured particles fall, another focal length is, if necessary, brought into the beam path of which the measuring range still just reaches over the largest measured particles. Thereupon the apparatus determines the distribution of particle sizes again with the use of the previously selected focal length and evaluation mathematics matched to this, the distance between the photo-detector (20) and the imaging device (18) being matched to the respective focal length disposed in the beam path. Distributions of particle sizes of unknown samples are thus measured with higher resolution and accuracy.
A device for determining the values of a parameter of particles, especially of water droplets, includes a measuring element having a measuring region that is intended to accommodate the particles. An illumination device illuminates the measuring region with a light beam, and an image acquisition device, having a camera, acquires an image of the measuring region illuminated by the illumination device. A processing device determines the values of the parameter from the image acquired by the camera. To determine the values of the parameter, the illumination device produces point illumination using a light beam whose light rays are focused on an objective optic of the image acquisition devices.
A system and method for detecting and quantizing particle fallout contamination particles which are collected on a transparent disk or other surface employs an optical detector, such as a CCD camera, to obtain images of the disk, and a computer for analyzing the images. From the images, the computer detects, counts and sizes particles collected on the disk. The computer also determines, through comparison to previously analyzed images, the particle fallout rate, and generates an alarm or other indication if the rate exceeds a maximum allowable value. The detector and disk are disposed in a housing having an aperture formed therein for defining the area on the surface of the disk which is exposed to the particle fallout. A light source is provided for evenly illuminating the disk. A first drive motor slowly rotates the disk to increase the amount of its surface area which is exposed through the aperture to the particle fallout. A second motor is also provided for incrementally scanning the disk in a radial direction back and forth over the camera so that the camera eventually obtains images of the entire surface of the disk which is exposed to the particle fallout.
A system and method are disclosed for the self-calibrating, on-line determination of size distribution and volume fraction of a number of particles dispersed in a medium by detecting multiply scattered light from the particles. The multiply scattered light is re-emitted in response to exposure to a light source configured to provide light of time varying intensity at selected wavelengths. The determination includes calculating the isotropic scattering coefficient for the particles at each of a number of wavelengths from the multiply scattered light as a function of an intensity modulation phase shift, and iteratively estimating the size distribution and volume fraction as a function of the isotropic scattering coefficient for each of the wavelengths. An estimation approach based on an expected form of the distribution and the mass of the particles is also disclosed.
A method and system for determining polycrystalline silicon chunk size for use with a Czochralski silicon growing process. Polycrystalline silicon chunks are arranged on a measuring background. A camera captures an image of the chunks. An image processor processes the image and determines the dimensions of the chunks based on the captured image. A size parameter associated with the chunks is determined.
A system (20) and method are disclosed for the self-calibrating, on-line determination of size distribution f(x) and volume fraction .phi. of a number of particles (P) dispersed in a medium (M) by detecting one or more propagation characteristics of multiply scattered light from the particles (P). The multiply scattered light is re-emitted in response to exposure to a light source (21) configured to provide light at selected wavelengths. The determination includes calculating the isotropic scattering and absorption coefficients for the particles (P) by comparing the incident and detected light to determine a measurement corresponding to the propagation time through the scattering medium (M), and iteratively estimating the size distribution f(x) and volume fraction .phi. as a function of the coefficients for each of the wavelengths. An estimation approach based on an expected form of the distribution and the mass of the particles is also disclosed. Furthermore, techniques to determine a particle structure factor indicative of particle-to-particle interactions which vary with particle concentration and influence light scattering at high concentrations is disclosed.
