dispersion factor dn

[verena]

Hi,
I try to optimize a lens system by setting up a merit function with
various variables.Therefor I defined the variable glass as a "model
glass". I attached refractive index to the merit function and
additionally dispersion factor for controlling the abbe number. My
question is what this factor actual means and which value belongs to
which abbe number.
Verena

[Brian]

On 11 Mar, 13:46, verena <verena.bagu...@gmx.de> wrote:
<snip>

what this factor actual means and which value belongs to
> which abbe number.
> Verena

Verena
The OSLO "DN" is not the dispersion dn - I know it is confusing! But
you need to be warned that
variable refractive index or dispersion nearly always result in
expensive or hard-to-work
glass types. "DN", the dispersion factor used as an OSLO, variable,
represents the position
of the glass between two lines in the n-dn diagram, one through N-SK16
("DN"=0) the other
through SF11 ("DN"=1) intersecting at N-FK5. So for glasses near N-FK5
it is indeterminate.
The table below gives RN and "DN" values for (in my view) the 16 most
useful glasses in
the Schott 2000 catalogue.

TYPE RN (nd) "DN" VCF
N-FK5 1.487490 -8.047618 70.404776
N-FK51 1.486561 22.762568 84.466758
K10 1.501371 2.155135 56.408319
N-BK7 1.516800 0.246045 64.166410
N-K5 1.522489 0.516614 59.481786
LLF1 1.548140 1.077440 45.749335
N-BAK4 1.568828 0.269384 55.974955
N-KZFS4 1.613360 0.542019 44.492981
N-SK4 1.612718 0.053254 58.633454
N-F2 1.620053 0.943485 36.430332
N-SK16 1.620410 0 60.322758
SF2 1.647689 0.944687 33.847676
N-LAK9 1.691002 0.051132 54.707594
N-SF15 1.698921 0.953651 30.200408
N-LAF21 1.788000 0.127851 47.487089
N-SF6 1.805180 0.980330 25.359284

Hope this helps.

Brian Blandford