Chromatische Vegrösserungsdifferenz? Why on one side only?

[Michael Cytrynowicz]

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

[Rene]

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

[Aljoscha]

Hi Mike,

check all adjustments of your light system. This looks to me like a poorly centered light beam.

Regards

Alexander

[Michael Cytrynowicz]

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

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

[Michael Cytrynowicz]

the 3 images

[Michael Cytrynowicz]

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.

[Michael Cytrynowicz]

the 3 images

[Rene]

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

[3nzo]

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

[Michael Cytrynowicz]

Rene and Enzo, great advice, I will check both (and report back here)

Thank you!

Grüss aus Oporto,

Mike

[piu58]

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.

[Michael Cytrynowicz]

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

[3nzo]

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

[Michael Cytrynowicz]

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

[3nzo]

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