Blog de diseño óptico
Telephoto
Telephoto
Ocular 10x Apocromático.
Petzval Lens-Own Design
In another post we already saw the necessary concepts to develop a "Peztval Lens". Based on that article, here I present my own design of a "Petzval Lens". It's an f/5 system, with a 5" focal and an HFOV of 10º, just like the one in the previous article. The difference with the other design is that I modify the crystals to maximize the quality of the system.
In this case, my design is a relaxed system (the standard of BFL being half of EFL is not met).
Here I use them as crystals:
-
M-TAF1(glass of Hoya with n=1.7725 and Vd=49.46)
-
F7 (glass of CDGM with n=1.6364 and Vd=35.39)
-
SF1 (glass of Schott with n=1.7174 and Vd=29.62)
-
TAFD33(glass de Hoya with n=1.8810 and Vd=40.14)
As you can see, for this design I use only Flint crystals.
The system has an EFL of 4.999", HFOV of 10º , f/5 with a total length of 5.57". The minimum distance between lenses has been set at 0.3" to allow sufficient space for the diaphragm.
Figure 1. Petzval system report.
The fundamental difference of this design with respect to the design of the problem has been the selection of crystals, which in this case seem critical, because the performance improvement is very big.
As can be seen in the system report, the RMS spot size is 3.608, 4.719 and 7.443 microns at 0º, 7º and 10º respectively. It is a very small point size, since the size of the Airy disc radius is 3.579 microns.
The OPD and Tranverse Ray Fan Plot graphs reflect that the 10º field is slightly affected by comma and spherical aberration. The total system comma is -1,391 waves and the spherical comma is 1,674 waves.
As you can see from the MTF graph, the performance of the system at 150 cycles per mm is between 25% and 30%, while the diffraction limit is around 45%, which indicates that the system could be improved by adding more lenses.
The distortion is less than 0.5% and the field curvature is less than 0.05". The system is achromatic at the 0.0 point of the pupil. The "maximum Focal Shift Range" is 153 microns, while the Ray Fan shows well compensated aberrations in general.
The lateral color is "limited difracted", being less than 1.5 microns. The illumination is over 90% in the 10º field.
If you found this article interesting, let me know. Below you have how to contact me.
Thank you very much and I'll see you later.