Feret diameter

Several diameter definitions are used in particle image measurements (Fig. 7). Martin diameter, the chord length which divides the projected particle into two equal areas with respect to a fixed dkection (29) Feret diameter, the projected length with respect to a reference dkection (30) and the diameter of equivalent surface area, the diameter of a ckcle the area of which is equivalent to the projected area of the particle in question (3). 

Fig. 7. Definition of diameteis frequently used in image analysis (a) horizontal Martin diameter, (b) horizontal Feret diameter, and (c) diameter of equal...

Image analysis can be used to determine a variety of morphometric parameters including area, Feret s diameter, Martin s diameter, aspect ratio (ratio of minimum to maximum Feret diameter), perimeter, length, width, and form factor (the ratio of area/[perimeter]2), which can be related to specific particle shapes. Some of these functions are illustrated in Fig. 10 [14]. In addition, quantitative methods have been developed to measure particle shape [2,15,16]. 

Perimeter, Hausner shape factors, Martins diameter, Feret diameter, two dimensional sphericity, rugosity. 

Fig. 13. a Maximal (Fmax) and minimal (Fmin) Feret diameters of a Saccharomyces cerevisiae budding cell Schematic representation of an unbranched filament (b), its skeleton (c) and its EDM image (d)... 

Fig. 2.2 The projected area of a particle is orientation dependent. Martin s diameter (i/ ) is 246 pm, the Feret diameter dp) is 312 pm and the projected area diameter in stable orientation d ) is 252 pm (the particle is the same as in Figure 2.1)...

The easiest diameter to measure is the Feret diameter but this is significantly larger than the other two diameters for most powders. It is probably best to reserve this diameter for comparison purposes and for rounded particles. Of the other two diameters, the projected area diameter is preferred since two dimensions are included in one measurement and the projected area is easier to estimate using globe and circle graticules than the length of the chord that bisects the image. 

The Lark counter [94] was designed for measuring particles in a loose powder, recording the sizes by the use of a series of pinholes in a chart. By ruling lines on the chart corresponding to a scale of sizes, and counting the pinholes between them, the size distribution in terms of the Feret diameter could be determined at a rate of about a thousand particles per hour. 

Optomax V is a simple to use automatic image analysis system employing dual microprocessors combined with high speed measurement circuitry. The system uses up to four high performance TV cameras to provide direct viewing of macroscopic or microscopic images. It counts and measures image features such as area, perimeter, Feret diameters, horizontal and vertical intercepts and so on. 

Mean path of gas molecules m ft %.max90 Feret diameter measured 90° to the m in... 

Feret s Diameter Feret s diameter is determined from the projected area of the particles by using a slide gauge. In general it is defined as the distance between two parallel tangents of the particle at an arbitrary angle. In practice, the minimum Xjrmm d maximum Feret diameters the mean Feret diameter Xp, and the Feret diameters obtained at 90 to the direction of the minimum and maximum Feret diameters X/rmax9o used. The minimum Feret diameter is often used as the diameter equivalent to a sieve analysis. 

The aspect ratio / (0 < / < 1) is defined by the ratio of the minimum to the maximum Feret diameter = FeretmiiAFeretmax- It gives... 

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