Image analyses are and have always been indispensable tools in particle studies. Conventional microscopic analysis has advantages over other methods in that it can provide information on size, shape, surface texture and some optical properties of individual particles in great detail. Microscopic analysis has often been the final judge of the size of monodisperse standard reference materials. However, the biggest drawback of conventional microscopic analysis is that the number of particles in focus that can be inspected in any field of view is limited. Thus, for a polydisperse sample, an adequate statistical representation of the entire sample can be an exhaustive, if not impossible, task.

Conventionally, captured images from microscopic measurements are recorded on photographic papers followed by manual study of the shape, size or surface morphology of the particles in the images. Nowadays, using computer automation, images can be captured and viewed directly on a monitor and digitized and recorded into computer files at a rate of millisecond or even microsecond. These images then can be reprocessed (e.g., by image enhancement) and analyzed using an image analysis program. Particle dimensional measurement (size, area, or cord length), particle count, shape analysis, and even fractal analysis can be accomplished by image analysis. Because of its rapid image capturing capability, more particles can be analyzed by continuously delivering them, either in liquid or in air, to the location of image capturing. This technique is then called dynamic image analysis.

In a dynamic image analysis device, the image capture procedure is accomplished using illumination of light combined with a sample cell and a CCD device. A frame grabber card then transfers the image to computer for further analysis. Depending on the optic setup, the size range of particles that can be analyzed using a dynamic image analyzer is between a few microns to a few millimeters.