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Forum: Processes Involving Optical Photons
Re: Question Surface Parameters of Unified Model (Susanne Jungmann)
Date: 22 Sep, 2010
From: Gumplinger Peter <Gumplinger Peter>

Dear Susanne,

> What would be simulated if one took dielectric_metal and groundbackpainted?

The groundbackpainted option exists only for dielectric_dielectric surfaces.

If you define your surface to be dielectric_metal, then, within the UNIFIED model, and for a 'ground' finish, the type of reflection is sampled from the reflection probabilities you've set for that surface ("SPECULARLOBECONSTANT", "SPECULARSPIKECONSTANT", and "BACKSCATTERCONSTANT"). If you don't set any of these, the default is 100% LambertianReflection. If you set the finish to 'polished' you get 100% specular spike reflections regardless of what types of UNIFIED probabilities you might have set.

The 'backpainted' option should be used for situations when there is a narrow gap between the radiator and the reflector. You can specify the index of refraction of this gap (as in a loose wrapping). The backing reflector in the case of 'groundbackpainted' is Lambertian (for 'polishedbackpainted' it is specular spike), while the interface between the radiator and the gap is modeled according to the UNIFIED reflection probabilities you might have set (see above).

> Concerning polishedbackpainted: As I understood, sigma_alpha is ignored,

> but not the Unified parameters. So contrary to an earlier post, there

> will be spike,lobe, backscattering or Lambertian (depending on the

> parameters one sets) reflection at the interface crystal/gap and only

> spike reflection (= specular refelction) at the backing!

Almost all you wrote is correct, except, if lobe reflection is the probability sampling result for the interface crystal/gap, the facet normal is then sampled from a distribution defined by sigma_alpha. So, sigma_alpha is not ignored (but, yes, it's ignored for the reflection from the backing).

Hope this clarifies the situation, Peter

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1 Question: Re: Surface Parameters of Unified Model   (Susanne Jungmann - 26 Sep, 2010)
(_ Feedback: Re: Surface Parameters of Unified Model   (Gumplinger Peter - 27 Sep, 2010)
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