Article: Examining a "decentered" objective

[Macro_Cosmos]

Hi,
Please share some advice on this article, especially regarding the technical aspects.
Would be great if anyone with experience of such a weird objective illuminate my mind a bit. There is an oil version of this objective as well, is it similarly weird?
https://wordpress.com/post/macrocosmosb ... ss.com/531

I have scheduled a meeting with local Olympus engineers to test the objective but it's now postponed because I got that 19 virus thingy, time to lock myself in. I decided to release the article early, would love some advice. Maybe there is something I missed, better be prepared for the testing!
Another issue I have yet to elaborate in my article, the microscope I am using has been repaired. There could be a slight misalignment between the plate that holds the nosepiece and the optical axis, that was where a repair took place. However, I cannot see any with my other plan-corrected objectives. Maybe I should take it to a gauge indicator.

I have this, which I think might be decentered.


Full resolution files are available, check the links in the article.
Full:
(Correction: 60xW is the middle one, 40x Dry is the right one)


Centre:


Corners:


Beads:

Perfect 60x:


Video:
https://youtu.be/RdH_uHUTX8c
This video not only demonstrates that the field is not flat, but it also shows it is unevenly flat. The right side is distinctively worse.
2 objectives, the second segment is the 60x.

Thanks and enjoy!

[Pau]

Without experience with this kind of stuff I only could drop few comments and questions.
- First, nice article and detailed observations! I concur: the objective seems to be decentered.
- What's the sensor size and secondary magnification (if any)? You said that the FN is 22mm so, as you well know this is a relevant question. For example with a FF sensor a 2.5X projective would be adequate.
- Do you observe the corner degradation and decentering inside a 22mm circle? If not, the objective couldn't be considered defective despite not being perfectly centered.
- Is the objective parcentric with the others you have? (lack of parcentricity could be indicative of objective decentring although also could be due to the nosepiece or other parts). You could test it exchanging the position in the nosepiece with other objectives
- As you suggest the main goal is resolution, not nice wide field uniformity. In the center resolution seems excellent, even better than with your 60W. (maybe DIC is not the most adequate illumination for maximum resolution and even less for comparing objectives with different DIC components)

Interesting stuff, please keep us informed!

[Macro_Cosmos]

Without experience with this kind of stuff I only could drop few comments and questions.
- First, nice article and detailed observations! I concur: the objective seems to be decentered.
- What's the sensor size and secondary magnification (if any)? You said that the FN is 22mm so, as you well know this is a relevant question. For example with a FF sensor a 2.5X projective would be adequate.
- Do you observe the corner degradation and decentering inside a 22mm circle? If not, the objective couldn't be considered defective despite not being perfectly centered.
- Is the objective parcentric with the others you have? (lack of parcentricity could be indicative of objective decentring although also could be due to the nosepiece or other parts). You could test it exchanging the position in the nosepiece with other objectives
- As you suggest the main goal is resolution, not nice wide field uniformity. In the center resolution seems excellent, even better than with your 60W. (maybe DIC is not the most adequate illumination for maximum resolution and even less for comparing objectives with different DIC components)

Interesting stuff, please keep us informed!

- PE2.5x used, 35mm format.
- The decentering is clear with my 26.5mm eyepieces, not sure which portion but it is in my opinion well into the 22mm circle
- Parcentric: Not entirely, and this is due to alignment

Resolution is important, a flat field is not, but a major portion of 2 of the 4 corners being that bad will become an issue. The 60x stack used a different type of DIC and I did not make any efforts to match the effects. The slices are very thin with de Senarmont retardation, using more steps would help. Epi-fluorescence was used for the beads, which should remove any variation regarding the condenser and establish a good standard.

That said, I do not think an NA of 1.15 and 1.2 would yield visible resolution differences. The 40x could be a little sharper in the centre due to the lack of plan-correction, since more complicated designs and more lens elements are needed to achieve that.

I have 2 friends with similar objectives -- some kind of apochromat that is not plan-corrected.
- corners suck
- field number says 22 but often barely 20mm
- resolution is better than plan-corrected counterparts as long as corners are ignored
This kind of corner difference was unheard of, but both said they would not be too surprised.

[Macro_Cosmos]

Visited Olympus last Wednesday, nothing they can do to fix it, it will have to go to Japan and the cost will be similar to buying a new one, so I declined.
Verified a few things, most are known but coming from an Olympus engineer, this installs some more confidence.
- projection eyepieces crop objectives to a 22mm "circle" (not strict terms)
- projection eyepieces bring slight distortion
- The lack of plan-correction combined with above could cause such issues, the objective was released and designed after those eyepieces have been discontinued. They were never supposed to officially work with the eyepieces

So should I do now? Try direct projection to see if there is the same problem. I no longer have any U-TLUs, I have a couple superwide tube lenses taken from their respective trinocular heads, I will have to try and utilise those.
I have an adaptor that allows tiny pitch and yaw adjustments, perhaps that can be used to counter the unevenness.

Back to the drawing board I guess, I need to find a way to mount the tube lens.

[Scarodactyl]

A u-tlu will noticeably underperform a superwide tube lens in the corners, probably an unwanted variable in your tests. It seems like you have a solid diagnosis for the lens already though. Maybe it can be mitigated as you suggest, but I wouldn't bet on it.

[abednego1995]

Perhaps the adaptive optics path like Hubble? just kidding. There's a guy certified to do third party objective repairs for Nikon, not sure if he does Oly.. (wait, I think it's no longer Olympus, Evident Life Science... whatever.), but I see him doing insane repairs on about everything.

https://twitter.com/ObjectiveGuy19

[Scarodactyl]

Wow, 'Evident' is a terrible brand name. I wonder what consultant firm they paid millions of dollars to to suggest they make their brand indistinguishable from the many dozens of whitebox importers crowding the space.
Plus side, checking their site let me see they'd announced their IotY award winners, with at least one name I recognized(!)

[rjlittlefield]

announced their IotY award winners, with at least one name I recognized(!)

I assume this refers to https://www.evidentscientific.com/en/press-releases/ioty2021/ .

Thanks for the leads -- I see three names there of people that I've talked with. It's a small world!

--Rik

[Macro_Cosmos]

announced their IotY award winners, with at least one name I recognized(!)

I assume this refers to https://www.evidentscientific.com/en/press-releases/ioty2021/ .

Thanks for the leads -- I see three names there of people that I've talked with. It's a small world!

--Rik

Yep, they are now called Evident, a new plaque was erected at their Sydney office too. I asked them about the name change, it "could have been better but it is what it is, the connections with customers matter the most".
The name change occurred around the near-end of last year, we had numerous issues with billing because of that. The official announcement was made on the first of April, some of which thought it was a cringe joke...

Perhaps the adaptive optics path like Hubble? just kidding. There's a guy certified to do third party objective repairs for Nikon, not sure if he does Oly.. (wait, I think it's no longer Olympus, Evident Life Science... whatever.), but I see him doing insane repairs on about everything.

https://twitter.com/ObjectiveGuy19

AO will become mainstream in the microscope world in the upcoming decade. Eric Betzig had some colourful language about the slow adoption of this technology, little too inappropriate for the forum. AO has apparently been mainstream in telescopes for decades. Thanks for sharing the repairs guy's Twitter, I will ask for his opinion.