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Imaging particle analysis is a technique for making particle measurements using [[digital imaging]], one of the techniques defined by the broader term [[particle size analysis]]. The measurements that can be made include [[particle size]], particle shape (morphology or [[shape analysis (digital geometry)|shape analysis]] and [[grayscale]] or [[RGB color model#Numeric representations|color]], as well as distributions (graphs) of [[Population (statistics)|statistical population]] measurements.
==Description
Imaging particle analysis uses the techniques common to [[image analysis]] or [[image processing]] for the analysis of particles. Particles are defined here per [[particle size analysis]] as particulate solids, and thereby not including atomic or sub-atomic particles. Furthermore, this article is limited to [[real image|real images]] (optically formed), as opposed to "synthetic" (computed) images ([[computed tomography]], [[confocal microscopy]], SIM and other [[super resolution microscopy]] techniques, etc.).
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As faster computing resources became available at lowered costs, the task of making measurements from microscope images of particles could now be performed automatically by machine without human intervention, making it possible to measure significantly larger numbers of particles in much less time.
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The basic process by which imaging particle analysis is carried out is as follows:
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4.) The measurements saved for each particle are then used to generate image population statistics, or as inputs to algorithms for filtering and sorting the particles into groups of similar types. In some systems, sophisticated [[pattern recognition]] techniques may also be employed in order to separate different particle types contained in a heterogeneous sample.
==Image
Imaging particle analyzers can be subdivided into two distinct types, static and dynamic, based upon the image acquisition methods. While the basic principles are the same, the methods of image acquisition are different in nature, and each has advantages and disadvantages.
===Static
Static image acquisition is the most common form. Almost all microscopes can be easily adapted to accept a digital camera via a [[C mount]] adaptor. This type of set-up is often referred to as a [[digital microscope]], although many systems using that name are used only for displaying an image on a [[Video monitor#video display|monitor]].
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The major advantages to static particle imaging systems are the use of standard microscope systems and simplicity of [[depth of field]] considerations. Since these systems can be made from any standard optical microscope, they may be a lower cost approach for people who already have microscopes. More important, though, is that microscope-based systems have less depth of field issues generally versus dynamic imaging systems. This is because the sample is placed on a microscope slide, and then usually covered with a [[cover slip]], thus limiting the plane containing the particles relative to the [[optical axis]]. This means that more particles will be in acceptable focus at high magnifications.
===Dynamic
[[File:Basic flow through diag on white.png|thumb|Diagram showing flow-through architecture for dynamic imaging particle anaysis.]]In Dynamic image acquisition, large amounts of sample are imaged by moving the sample past the microscope optics and using [[flash (photography)#High speed flash|high speed flash]] illumination to effectively "freeze" the motion of the sample. The flash is [[synchronization|synchronized]] with a high [[shutter speed]] in the camera to further prevent motion blur. In a dry particle system, the particles are dispensed from a shaker table and fall by gravity past the optical system. In fluid imaging particle analysis systems, the liquid is passed perpendicular past the optical axis by use of a narrow flow cell as shown at right.
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