Scatterers - Tabulated PSD

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Tabulated PSD

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Description

Description

The Tabulated Power Spectral Density (PSD) scatter model accepts measured PSD data (1D or 2D) and creates an interpolated BSDF model.

Navigation

This feature can be accessed by selecting Tabulated Power Spectral Density (PSD) as the Scatter Type in the Create a new scatter model dialog box.

Controls

Control	Inputs / Description	Defaults
Name	Name of the model (required).	Scatter n
Description	Description of the model (optional).
Type	Select Tabulated Power Spectral Density from the pull down menu.	Lambertian
Additional Data
Wavl(ref)	Reference wavelength	0.587
Delta N	Refractive index difference between incident and substrate material. For reflection, Delta N = 2.	2
Refl/Tran	Reflectance/transmittance of surface.	1
File	Full path to file containing measured data.
# Points	Number of data points in file.	0
Freq(min/max)	Minimum and maximum frequency represented in file data.	0,0
PSD at min	PSD value at minimum.	0
PSD at max	PSD value at maximum.	0

OK	Accept settings and close dialog box.
Cancel	Discard settings and close dialog box.
Help	Access this Help page.

Application Notes

BSDF function

The BSDF is derived from the PSD from the following equation,

where Dn is change in refractive index at the scattering interface (Dn = 2 for mirrors), S(f_x,f_y) is the 2D PSD, Q is the surface reflectivity and the indicies i and s refer incident and scatter directions. See 'Optical Scattering: Measurement and Analysis,' 2nd edition, John C. Stover, equation 4.1

Data file format

The file format for Tabulated PSD data is shown below. There is a two line header followed by data in two columns (freq PSD). Entries in [] are optional.

Frequency values are in units of mm^-1 while the 2D PSD values are in units of mm⁴. The linescan option shown above should be used if the PSD data is 1D and has units of mm³. In the case of 1D data, FRED will perform a numerical Abel transform to recover the 2D dataset.