Using modern olympus objectives on old olympus

[onilink_]

Hello,

I have an Olympus BH2, with the vertical illuminating system and infinity corrected objectives.

Default objectives are MSPlan objectives. But I also use with success (and a neutral eyepiece) two other objectives.
An Olympus Plan 100x/1.25 oil infinity/-

And a dry Zeiss 80x/0.95 infinity/- objective (I can take/post a picture if required, but I don't have one already taken).

I wanted to try a Olympus UPlanApo 40x/1.00 Oil Iris infinity/- objective, but sadly the results are not good, and I'm not sure why. The seller assures me that the lens is functional, so unless something went wrong during shipping, despite the good packaging, normally the problem does not come from the objective itself.

Here two captures using this objective (with 1.0x mag and 1.5x on the Olympus magnification changer):

capture_full_50p.jpg (170.07 KiB) Viewed 1030 times

capture_zoom1.5x_50p.jpg (165.48 KiB) Viewed 1030 times

I noticed something weird. When I change the focus, the image does not blur in the usual way, but the out of focus image is moving to the bottom right side (instead of being centered).

And for comparison, one with the 100x objective (1.5x magnification):

100x_50p.jpg (166.74 KiB) Viewed 1030 times

So my main question is: is this the expected behavior?
I know some corrections are also made in the tube lens, but I don't think it explains the difference between my 100x/80x and this 40x.

So maybe it's the illumination system? I use a BH2-MA, and I think it's using Kölher illumination.
The field stop is not in focus when the image is in focus. Do you think the quality issue is just because of the different back focal plane of this objective, comparing to the other ones?

Thank you

[Scarodactyl]

I think your objective is decentered or otherwise borked. Darn shame.
The tube lens in the bh2 illuminators is pretty neutral, the far corners on aps-c seemed to do something when I had one but I didn't test it that well. Either way it is fairly ckmpatible with modern olympus.

[onilink_]

I think your objective is decentered or otherwise borked. Darn shame.

Oh no

Any tests I can do to verify this?

Edit:
I made some videos of the focusing, just to be sure:
https://youtu.be/fFSmYJn81VM
https://youtu.be/ASY_i08vNC4

[Alexander]

I know some corrections are also made in the tube lens, but I don't think it explains the difference between my 100x/80x and this 40x.

Reconsider that point.

[Scarodactyl]

Reconsider that point.

The 100x and 40x in this test are made for the same optical system so if that were the issue you would expect both to perform poorly. That's aside from this combination being something of a known quatity from previous testing.

If you can return this objective I'd try that.

[onilink_]

I can return the objective, that's why I want to know for sure.

I know some corrections are also made in the tube lens, but I don't think it explains the difference between my 100x/80x and this 40x.

Reconsider that point.

Do you think because it is an apochromat it will pose more problem than my other objectives?

I'm thinking about keeping this objective if I'm sure it is functional, and to buy an Olympus BX microscope one day.
But if the objective is defective I can't afford to keep it, given its price (500€).

Note: I will use it for light reflected microscopy only. It's not a problem right?

[apochronaut]

Scarodactyl is correct. The objective has most likely been disassembled without observing and marking the original alignment of the lens cells and then reassembled carelessly. The seller is incorrect. The objective can likely be repaired but with considerable effort and time.
I would try to return it, if possible. If it is an ebay purchase, and the seller balks ; even if the listing said no returns, if it was described as fully functional and works as intended, you can start a return request since it is likely covered under buyer protection. If the seller doesn't comply within the alotted time, ebay will refund you.

[onilink_]

Scarodactyl is correct. The objective has most likely been disassembled without observing and marking the original alignment of the lens cells and then reassembled carelessly. The seller is incorrect. The objective can likely be repaired but with considerable effort and time.
I would try to return it, if possible. If it is an ebay purchase, and the seller balks ; even if the listing said no returns, if it was described as fully functional and works as intended, you can start a return request since it is likely covered under buyer protection. If the seller doesn't comply within the alotted time, ebay will refund you.

Thank you. I will return it.

Just out of curiosity, is it the quality of the image on my BH2 system or the videos of the change of focus that allow you to say this?

[apochronaut]

Mainly the skewed focus. This can be caused by a slight de-lamination. I have seen an Olympus 160mm 45mm parfocal planapo objective where a bottom element in a cell just ever so slightly dropped out of it's mount. It was air spaced with a tiny gap above the upper lens in the lower cell, and dropped to contact that lens. It gave similar symptoms. The problem is not that hard to repair.

Similar symptoms are caused by the rear lens group being off center. It is often separated from the main lens stack by a lengthy spacer leaving it vulnerable to being splayed off axis if the mechanical tolerances are a bit sloppy or there is ganged shimming . Usually the rear group needs to be rotated a full 360 and checked every 45° or so for axial alignment but some objectives are weaker than others in this regard.
If there is any evidence at all of the objective having been dismantled, that might be the culprit.

[onilink_]

Thank you very much for the detailed answer.

I don't think the objective have been dismantled.
It was a demonstration objective from what the seller told me. So it should be almost new.

Too bad.

[apochronaut]

I wonder what they were demonstrating?