Lens in vacuum

[mattemilio]

Thanks for this great project.
And sorry for the potential stupid question.
I can define an ideal material (e.g. vacuum).
But I didn't understand how to pass it to optic.add_surface function.
Could you please help?
Many thanks in advance

[HarrisonKramer]

Hi @mattemilio,

Please see this example: https://optiland.readthedocs.io/en/latest/gallery/specialized_lenses/infrared.html

Essentially, all you need to do is pass the material directly to the add_surface function:

silicon = materials.IdealMaterial(n=3.4222)
lens.add_surface(index=1, radius=2.0721, thickness=0.1340, material=silicon)

Hope this helps.

Regards,
Kramer

[mattemilio]

Thanks a lot!

[mattemilio]

Hi @HarrisonKramer,
sorry to somehow reopen the topic.

"air" is the default material when add_surface is called and I see in material_factory in the _configure_post_material function that "air" is treated as an Ideal material with refractive index 1.0 and no absorbtion

But refractive index of air is not really 1.0 (that would be vacuum)

For some optical systems (e.g. dioptric systems for satellite applications) the difference might not be negligible

What do you think?

Thanks a lot and again congratulations for the excellent work

Kind regards,
Matteo

[HarrisonKramer]

Hi @mattemilio,

No worries at all, and thanks for the kind words!

You're right. The physical refractive index of air is slightly above 1.0, but in many optical design tools (including Optiland), it's conventionally treated as exactly 1.0 because glass catalog data is specified relative to air. So when we define air as an ideal material with n=1.0, we're following that convention.

For high-precision systems like satellite optics, the small difference can indeed matter. I saw your recent PR to allow index adjustments based on temperature and pressure - thanks again for contributing that! I haven’t had time yet to review it in detail, but it looks like a great step toward enabling more physically accurate modeling using empirical corrections.

Thanks again,
Kramer