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Re: [ATM] Attempted Parametrization of a Petzval Design
Attila Schné wrote:
>
>Dou you use Zemax to design these lenses? Can you give me suggestion
>how can I use the optimisation function in Zemax?
>
>I have not to much knowledge about it.
>
Actually, I used the GSUM tool to design the doublet. Then I used
ZEMAX to test the Petzval design.
I want to preface the rest with the note that I don't think I've
found two people who agree on merit functions. Many will
totally disagree with mine. Also, you should really read the
optimization chapter in the User's Guide. You may also have to
go back to previous chapters to get the background for the
optimization discussions.
In April 2000, George Anderson sent us Roland Christen's 11 inch
Petzval Design. That design consists of two air-spaced N-K5/F2
doublets. Each doublet has isoconvex crown element and mating
inner radii. Attempting to parametrize that design in ZEMAX:
First, the desired effective focal length had to provide a
given f/#:
Num Type Int1 Int2 Target Weight
2 CONS 7.50000E+000 0
3 EPDI 0.00000E+000 0
4 PROD 3 2 0.00000E+000 0
5 EFFL 6 0.00000E+000 0
6 DIFF 5 4 0.00000E+000 0
7 CONS 1.00000E+000 0
8 PROD 7 6 0.00000E+000 1
Second, the desired doublet to doublet separation had to be a
given fraction of the focal length:
Num Type Int1 Int2 Target Weight
10 CONS 8.77745E-001 0
11 PROD 10 5 0.00000E+000 0
12 TTHI 5 5 0.00000E+000 0
13 ETVA 5 0 0.00000E+000 0
14 MINN 12 13 0.00000E+000 0
15 DIFF 14 11 0.00000E+000 0
16 CONS 1.00000E-001 0
17 PROD 16 15 0.00000E+000 1
I need to calculate semi-diameters (ZEMAX supplies diameters):
Num Type Int1 Int2 Target Weight
19 CONS 5.00000E-001 0
ZEMAX does not allow specification of isoconvexity and
fixed edge thickness. Consistent with the design of the
GSUM tool, I specify the minimum thickness as a fraction
of the semi-diameter, but with different values for convex
and concave lenses; I know this gives a discontinuity at
the boundary, but ...
Num Type Int1 Int2 Target Weight
21 CONS 1.25000E-001 0
22 CONS 1.50000E-001 0
Semi-diameter of the first doublet:
Num Type Int1 Int2 Target Weight
24 DMVA 2 0.00000E+000 0
25 PROD 24 19 0.00000E+000 0
Edge thickness of the convex lens in the first doublet.
Num Type Int1 Int2 Target Weight
27 ETVA 2 0 0.00000E+000 0
28 DIVI 27 25 0.00000E+000 0
29 DIFF 28 21 0.00000E+000 0
30 CONS 5.00000E+000 0
31 PROD 30 29 0.00000E+000 1
Central thickness of the concave lens in the first doublet.
Num Type Int1 Int2 Target Weight
33 TTHI 4 4 0.00000E+000 0
34 DIVI 33 25 0.00000E+000 0
35 DIFF 34 22 0.00000E+000 0
36 CONS 5.00000E+000 0
37 PROD 36 35 0.00000E+000 1
Semi-diameter of the second doublet:
Num Type Int1 Int2 Target Weight
39 DMVA 6 0.00000E+000 0
40 PROD 39 19 0.00000E+000 0
Edge thickness of the convex lens in the second doublet:
Num Type Int1 Int2 Target Weight
42 ETVA 6 0 0.00000E+000 0
43 DIVI 42 40 0.00000E+000 0
44 DIFF 43 21 0.00000E+000 0
45 CONS 5.00000E+000 0
46 PROD 45 44 0.00000E+000 1
Central thickness of the concave lens in the second doublet:
Num Type Int1 Int2 Target Weight
48 TTHI 8 8 0.00000E+000 0
49 DIVI 48 40 0.00000E+000 0
50 DIFF 49 22 0.00000E+000 0
51 CONS 5.00000E+000 0
52 PROD 51 50 0.00000E+000 1
A small air-space in the first doublet may yield ghosts.
This will have to be checked later. Absolute thickness
constraint on the air-space in the first doublet:
Num Type Int1 Int2 Target Weight
54 CONS 0.00000E+000 0
55 TTHI 3 3 0.00000E+000 0
56 ETVA 3 0 0.00000E+000 0
57 MINN 55 56 0.00000E+000 0
58 DIFF 57 54 0.00000E+000 0
59 OPGT 58 0.00000E+000 0
60 CONS 1.00000E-001 0
61 PROD 60 59 0.00000E+000 1
Absolute thickness constraint on the air-space in the
second doublet:
Num Type Int1 Int2 Target Weight
63 CONS 0.00000E+000 0
64 TTHI 7 7 0.00000E+000 0
65 ETVA 7 0 0.00000E+000 0
66 MINN 64 65 0.00000E+000 0
67 DIFF 66 63 0.00000E+000 0
68 OPGT 67 0.00000E+000 0
69 CONS 1.00000E-001 0
70 PROD 69 68 0.00000E+000 1
Optical performance:
Num Type Int1 Int2 Target Weight
72 DMFS
I selected the lens diameters, f/#, separation ratio,
wavelengths and field. After freezing the thicknesses and
radii (manual intervention):
Surf Radius Thickness Glass Diameter
STO Infinity -6.652961 290
2 1583.45 33 N-K5 300
3 -1583.45 5.55 300
4 -1583.45 22.5 F2 300
5 49432.3 1909.1 300
6 1017.51 22.4 N-K5 200
7 -1017.51 0 200
8 -1017.51 15 F2 200
9 61956.2 1046.915 200
IMA -3055.721 42.27809
The only bad ghost detected by ZEMAX is the reflection
between the lenses of the second doublet;-)
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