Very dear forum members,
{please forgive again my using English}
I am obtaining a lot of chromatic aberration - I believe it is CVD - but only on one side of the image.
All objectives, Plan or Planapo, and both a Zeiss KPL 10x and a Zeiss S-KPL 10x, always happening.
On my Zeiss Standard with the plain condenser 0,9x lens, it also happens with the 0,9x lens flipped on or off.
I have an Optovar 0,8 - 1,6x, it happens at all magnifications.
Any ideas of what can be causing this? Revolver (turret) misalignment?
aberration
I am attaching a "Rechts" and a "Links" images showing the aberration happening on one side of the micrometer, but not happening on the other side.
Also, even if I decenter the condenser, set Kohler, etc - still happens all the time...
Thank You from Portugal,
Mike
if you close the field iris and focus on it, how does it look like? Open and close the condensoriris, is the field iris asymmetrical in the fringes?
René
Hi Mike,
check all adjustments of your light system. This looks to me like a poorly centered light beam.
Regards
Alexander
Zitat von: Rene in Juni 16, 2024, 19:24:48 NACHMITTAGSif you close the field iris and focus on it, how does it look like? Open and close the condensoriris, is the field iris asymmetrical in the fringes?
René
Dear Rene, thank you!
I took 3 pictures - the first 2 have the field iris almost closed, and the condenser iris open. The 3rd image has the field iris more open, but the condenser iris closed.
Thanks!
Mike
the 3 images
Alexander, thank you!
It makes sense! - I am suspecting the 5-Fach revolver, and tried to center it as well as I could - I am adding an image of how I did it.
This happens when the light base is not exactly centered with the arm. Check whether the base is slightly loose, or one of the lens elements in the base tilted in the lightpath.
Good luck, René
Hi Mike,
the cause could also be the sensor not being parallel to the object plane. Have you checked if by changing the focus the CVD cancels out and appears on the other side?
Best regards.
Enzo
Rene and Enzo, great advice, I will check both (and report back here)
Thank you!
Grüss aus Oporto,
Mike
Good morning, I recommend taking some additional monochrome images, may be in green. So you can find if there is more than lateral chromatic error. If so, you may think about the reasons which may be problems with adjustment somewhere.
I recommend rotating all optical elements for which this is possible. Maybe you find the point of problems this way.
My dear Rene, Enzo and Uwe, I solved the problem (I think)! - I replaced the Zeiss 0,9x condenser with another one I had in a drawer, and the image improved dramatically. I will add a note and some images in a few moments.
Gruess aus Oporto,
Mike
Hi Mike,
what you say and the two-color image of the closed field diaphragm would confirm your hypothesis. Keep us updated and have a good evening.
Enzo
Liebe Mikrofreunde,
To continue the story (photos in order): I took apart the entire Zeiss Standard, trying to figure out where the misalignment could come from. Of course, I did not disassemble critical parts (z.B., Seidentopf, etc).
I even did a small light-path study (#1), but it was quite imprecise. Anyways, I did not see anything very obvious. I wish there was an easier way to collimate :-)
Then I had an inspiration, and removed the condenser. And yes, there was little CVD aberration (#2) across all objectives.
I had a spare condenser 0,9x in a drawer, a newer one, and I put it in. Well, almost all aberration was gone (#3) - so it was basically the condenser!!
With the aberration under control, and feeling confident, I proceeded to mesure the fields using a stage micrometer, for all objectives and Optovar settings (#4)
I was quite happy with the images I was getting through my Canon 80D with a Pentax 40mm pancake and EOS Utility (#5,6). These are for the beautiful Rhododendron W3ASimII slides Jörg Weiẞ gave me 10 years ago.
In the meantime, the fantastic LED adaptation from Stephan Hiller arrived, as well as a new Zeiss Phase Condenser IIz, Zeiss 40x PH2 and a Zeiss Planapo 2.5x from him. Of course, still no aberrations, and pretty decent Kohlering (#6)
I am very happy with the new images I am getting (#7,8 - my own Apium slides, the first is W3ASimII, the 2nd is Etzold, sorry I did not yet add the scale)
And of course, I will try to get better, by following the amazing people here in the forum, as well as the MKB.
The coffee shop here in Matosinhos has a great CVD aberration-free banner :-) (#9)
Thank you all, my friends
Grüß aus Porto,
Mike
Hi Mike,
this shows that the condenser is a fundamental element for obtaining good images. I believe that the quick coupling, now practically used on all microscopes, could be a cause of possible misalignment. I have verified that if you are not careful, the hook may seem well fixed, but this is not always the case, fractions of a millimeter off axis are enough to cause problems.
Best regards.
Enzo
Thank you Enzo.
With the firt (bad?) condenser I tried aligning it as much as I could, using the 3 screws, but could never get rid of the CVD. Aligning the new condensers worked very easily. Could it be a defective (or abused?) condenser?
A small note: image #3 shows a bit of pincushion.
Warm regards,
Mike aus Oporto
Hi Mike,
It could be a bad condenser. As for pincushion, I'm no expert, but I think it depends on the lens.
Best regards.
Enzo
Hi Mike,
alignment of the objective turret is normally done by a special tool called "Ringlineal" in German:
(https://up.picr.de/48165332dx.jpg)
This tool is screwed into the objective turret instead of an objective with the table fully lowerd. Then the "Ringlineal" is mooved into observation position and the allen screw fixing the turret is slightly lowerd (as you did) and the table is lifted until the rim of the Ringlineal is touching the table without forming a visible gap beween its lower rim and and the object table. In this position the turret is fixed with the allen screw again. This ensures a perpendicurar orientation of the turret to the table and by this parallel to the optical beam path.
Regards
Stephan
Hi Stephan,
the microscope column and the travel axis must be parallel to use the Ringlineal. Furthermore, the table must be exactly orthogonal to this axis. With which tool can you control all this?
Thanks and best regards.
Enzo
Hi Stephan and Enzo - very interesting to learn what you both are saying, I will keep my eyes and ears open!
Gruess aus Porto,
Mike
P.S. Germany 90th minute. Wow!
Hi Enzo,
you are absolutely right. The usage of a Ringlineal requires the table to be orthogonal to the light path and the travel axis of the table to be strictly parallel with the light path. With a solid old microscope (e.g. Leitz or Zeiss) not damaged by a drop from a larger height, with all movements still smoothly working, this is normally given by its construction. I never had a problem with this in any of my Leitz or Zeiss microscope stands I have, even after a complete disassembly of the stand (table and drives). The claening and re-lubrication of an objective turret, however, often requires the disassembly of the turret from the stand. Remounting the refurbished turret is easily done by the help of a Ringlineal especially when the turret is not pinned with the column.
Exchanging a fix turret with a dovetail mounted turret on a Zeiss GFL, Standard or Junior microscope is also a typical case for using a Ringlineal for realigning the turret correctly.
Mike had loosen the screw which fixed the turret in the correct position. Realigning the turret then should be done by a Ringlineal.
Regards
Stephan
Dear Stephan, I am completely convinced :-)
I believe I am still slightly misaligned - the light path is a bit North of center, so yes, I should follow the procedure you mention. Now the question is, where do I get a Ringlineal?
And, now that you did mention, the thought of exchanging my 5-fach turret for a 7-fach dovetail one DID cross my mind, if I can align it with the Ringlineal :-)
Friendly regards from Porto,
Mike
Hi Stephan,
other microscopes, such as my Zeiss Jena Amplival, have interchangeable objective turret, turret arm and table. This poses alignment and orthogonality issues due to the dovetail of the turret and table attachment.
With interchangeable lens turrets, an alignment with the Ringlineal may not be resolved if you act on the fixed part because the turrets may have a different misalignment.
Finally, other microscopes such as the larger Lomo ones (e.g. MBB-1A) have the focusing stroke on rollers and parallelism is obtained by acting on threaded blocks.
However, the Ringlineal remains an indispensable tool for understanding the state of the microscope. Where could it be found?
Thanks and best regards.
Enzo