Key
Features
Click an icon for more information
|
|
|
|
FRAUNHOFER THEORY |
 Assumptions
Spherical, non-porous and opaque particles,
Diameter d > wavelength l,
Particles are distant enough from each other,
Random motion,
All the particles diffract the light with the same efficiency, regardless of.
Characteristic of the Airy shape
Circular,
Consisting in concentric rings I = f (a),
Spacing and size of the rings are linked to the particle size,
The fist zero angle is related to the diameter d by 1.22 l/d,
75% of the total energy is concentrated in the first lobe.
Principle
Aspect of the diffraction pattern with respect to the particle size
System
for a large particle |
System
for a small particle
|
The observation of the diffraction pattern at finite distance is done through a lens (L) placed between the laser source and the detector
The diffraction patterns of particles having the same size converge at the same point whatever them location with respect to the lens,
The first zero on the detector is 1.22 lf/d where f is the focal length.
|
| MIE THEORY |
The Fraunhofer theory is applicable for large particles compared to the wavelength l (diffusion and absorption are not considered).
For smaller particles, it is appropriate to use Mie Theory.
The Mie model takes into account both diffraction and diffusion of the light around the particle in its medium.
To use the Mie model, it is necessary to know the complex refractive index of both the sample and the medium.
This complex index has a real part, which is the standard refractive index, and an imaginary part, which represents absorption.
Complex index = m
m = a + b
a : real part
b : imaginary part
Because of the importance of this model, CILAS has crated a fast algorithm, which enables the user to get, within seconds, diffusion results using Mie theory and taking into account the complex index of the sample. |
|
|
 |
Come and see our solutions at the following trade shows:
International
Conference & Exhibition on Advanced Ceramics & Composites
Booth 223
Daytona Beach, FL
January 29 - 30, 2008
Pittcon 2008
Booth
1960
New
Orleans, LA
March
1 - 7, 2008
Particle Society of
Minnesota
Roseville, MN
March 19, 2008
International
Powder & Bulk Solids Show
Booth 2655
Chicago,
IL
May
5 - 8, 2008
American Coatings Show 2008
Booth 929
Charlotte, NC
June 3 - 5, 2008
MS&T 2008
Pittsburg,
PA
October 5 - 8, 2008
American Association of Pharmaceutical Scientists 2008
Booth 240
Atlanta, GA
November 16 - 20, 2008
|
|
|
|
