Zemax issue with coatings 1

[Andy2000]

Hello,

I am using the NSC part of Zemax to model a slap of glass sitting on a black absorbing surface. It seems that Zemax does not have an option to model the thin film of air between the glass and absorbing surface.

I tried many different coatings, including making my own one in the COATING.DAT file but without success. Doing a glass-glass interface or glass-air interface works fine though.

Any ideas why? Currently I am shifting all the objects by a fraction of a mm above the surface but it is a rather messy solution.

Thanks in advance!

Andy

 

[lumenharold]

My impression of ZEMAX is that it is a very literal representation of the system being modeled. If you have a thin layer of air then that is what ZEMAX will expect to have defined between the surfaces. Glass/air interface into air then the air/black surface interface. I don't think you can have air defined as a coating as a coating needs to have an index greater than one (1).

Harold
SW2010 SP3.0 OPW2010 SP1.0 Win XP Pro 2002 SP3
Dell 690, Xeon 5160 @3.00GHz, 3.25GB RAM
nVidia Quadro FX4600

http://www.lumenflow.com

 

[Andy2000]

Dear Harold,

thanks a lot. I will be adding a few um's of air underneath my glass slab.

I suspect what Zemax does is:
1) find the point of intersection between glass and absorbing surface.
2) tries to trace the reflection from the absorbing surface to the glass.
3) sees that the surface is absorbing and kills the ray.

What it does not do is to trace the ray from the surface of the glass through the coatings and then to the surface of the absorbing object. This is to save CPU time. In most cases there is no need to propagate the ray twice through the coatings (in and out) as you can pre-compute their combined effect.

Thanks a lot for the advice,

Andy