SCATMECH > Classes and Functions > Surface Scattering Models > Focussed_Beam_Instrument_BRDF_Model

class Focussed_Beam_Instrument_BRDF_Model

The class Focussed_Beam_Instrument_BRDF_Model calculates the effective BRDF averaged for a converging beam incident upon a sample with a specfied BRDF. It accepts as a parameter another BRDF_Model a half angle for the incident cone and a focal position. Integration is performed over a right-circular incident code using a multi-point integration scheme based upon Gauss-Zernike integration.

Diagram showing a cone of angles incident upon a sample, focussed on a focus circle, and diverging at the detector circle.

Parameters:

Parameter Data Type Description Default
lambda double Wavelength of the light in vacuum [µm].
(Inherited from BRDF_Model.)		 0.532
type int Indicates whether the light is incident from above the substrate or from within the substrate and whether the scattering is evaluated in reflection or transmission. The choices are:
0 : Light is incident from the above the substrate, and scattering is evaluated in reflection.
1 : Light is incident from the above the substrate, and scattering is evaluated in transmission.
2 : Light is incident from the within the substrate, and scattering is evaluated in reflection.
3 : Light is incident from the within the substrate, and scattering is evaluated in transmission.
For 1, 2, and 3, the substrate must be non-absorbing.
Focussed_Beam_Instrument_BRDF_Model supports any type supported by model.
(Inherited from BRDF_Model).		 0
substrate dielectric_function The optical constants of the substrate, expressed as a complex number (n,k) or, optionally, as a function of wavelength.
(Inherited from BRDF_Model.)		 (4.05,0.05)
model BRDF_Model_Ptr The light scattering model.
Note: The parameters lambda, type, and substrate must match those of model.		 Microroughness_BRDF_Model
alpha double The half angle of the incident light cone [deg]. 0
integralmode int The integration order, ranging from 1 to 7. The number of points in the integration depends upon this order and are 1, 4, 7, 16, 21, 36, and 43 for orders 1, 2, 3, 4, 5, 6, and 7, respectively. 3
focal_point double This value is defined as the ratio of the sample-focal-point distance to the sample-detector distance. If the incident light is focussed onto the detector circle, the parameter is 1. If it is focussed at the sample, the parameter is 0. The parameter can take any real value. 1

See also:

SCATMECH Home,   Conventions,   Instrument_BRDF_Model,   dielectric_stack

NIST Digital Library of Mathematical Functions, Section 3.5(x), Numerical Methods, Quadrature, Cubature Formulas.

T.A. Germer and H.J. Patrick, "Effect of bandwidth and numerical aperture in optical scatterometry," Proc. SPIE 7638, 76381-F (2010).

Include file:

#include "focussedbeam.h"

Source code:

focussedbeam.cpp

Definition of public elements:

class Focussed_Beam_Instrument_BRDF_Model
  : public Instrument_BRDF_Model
{
};

For More Information

SCATMECH Technical Information and Questions
Sensor Science Division Home Page
Sensor Science Division Inquiries
Website Comments

Current SCATMECH version: 7.22 (April 2021)