Some time ago, I obtained a weird OEM 60x oil immersion objective. I'll call it the 60xO because I'm lazy.
The objective uses the same shell as those weird Nikon 20x objectives. More on that when I'm bothered.
The seller claimed it was for phase contrast. However, the internal annulus is far too small. It's similar to the ring of a Ph1 or PhL objective. Being a high NA oil immersion objective, will such a tiny ring even produce phase contrast effects? I don't know.
My speculation based on anecdotes and its construction concluded it's a UIS2 60x objective. I paid $300 for it. The main rationale was its spring loaded front assembly construction, opposed to UIS high magnification objectives having a recessing front tip, infamous for clogging up and not responding (mostly due to the user mishandling it).
I drafted a method that won't be too involved and will at least tell me whether this prism is UIS or UIS2. The method is very simple, just throw money at it. I've always wanted a water immersion objective because immersion oil drives me nuts. If I do get a 60x water objective, I'll get the DIC prism too, and it must be UIS2. With that DIC prism, I'll be able to easily determine the objective's technology and subsequently its age, with a small caveat. Nonetheless, an utter mismatch will summon radically weird banding issues, yielding a very weak DIC effect.
The DIC prism for 60x UIS2 objectives landed several days ago. After a busy but fun Christmas, I fired it up. It was compared against a UIS2 60x water immersion objective. I'll lazily refer to it as 60xW from now on. The Normaski slider I used was the U-DICT, compatible with my water immersion objective. 40x and 60x oil immersion UIS2 objectives are only officially compatible with the U-DICTS, where the BFP1 (back focus place) lever is engaged.
The results are almost identical. Indicating prism compatibility. If you're unaware, different objectives require different condenser Normaski prisms. UIS and UIS2 condenser prisms are usually incompatible. Mixing them will result in weird banding. It's complicated for UIS, as apos and fluorites use different prisms, so do their oil immersion counterparts. This is due to the different placement of the back focal plane. UIS2 unifies this placement among fluorites and superapochromats.
There is however a small distinction. Several oil immersion high power objectives officially require the U-DICTS (or the other exotic ones with the lever) with the BFP1 lever engaged. The BFP of the PlanApo 60x N (numerical aperture or NA=1.42) is -25mm, whereas the 60xW and 60xO-XApo (NA=1.42) has a BFP=-19.1mm. I do not have the ability to measure the BFP of oil immersion objectives. A simple method for dry objectives is shining a low wattage collimated laser through the front to project a round beam onto a piece of paper on the back, note the diameter of the beam and distance to the paper from the objective, and do it several times for different distances. Then just make a regression equation and find the distance where the diameter = 0, that's approximately the BFP location. Anyway, it's not as trivial for high power objectives. I don't know a good method.
Here's what prism mis-match looks like.
This isn't a one-to-one test due to the shear being inconsistent, but it's clear that the second image suffers from very odd banding (I inverted the colours to reverse the DIC bias), while the first one illustrates a very pleasant and uniform gradation. The DIC affect is also weak, as the objective side Normaski prism can't bring the light rays together. I cannot find much official data on the BFP of UIS objectives. What I do know is, they are a garbled mess. I'd love to have a source if possible.
Now, the comparsion.
Lowered global contrast due to the unfortunate annulus, causing light to be scattered. With added contrast, the sharpness levels are about the same. The 60xW has an NA of 1.20. The 60xO's NA is either 1.35 or 1.42. The condenser I'm using is equipped with a dry top lens, NA capped at 0.9.
I can safely say this is a UIS2 60x objective now. The question remains, which one? There's several UIS2 60x oil immersion apo objectives. HR versions, iris controlled, XApos (due to its age) and TIRF ones can be ruled out. This leaves us with 2 options. The SApo with an NA of 1.35 and the PlanApo N with an NA of 1.42. Both of these require the BFP1 lever to be engaged on the objective Normaski prism. My example didn't use such a prism, producing almost identical results. Is the difference between a BFP of -25mm and -19.1mm negligible for normal use? Of course, the UIS 60xO objectives might just have a BFP of -19.1mm as well, making prism mismatch here negligible. The chances of that seem low however. I've also observed the interference patterns using a phase telescope, they are identical between these 2 objectives. Puzzling!
At least there's progress, I love a good mystery. Next step is to identify the objective and make sense of its small yet thick phase annulus. I have a set of old phase annuli that's photoresistive film based. Maybe the smallest one is a match. After I've played with it more, I'll collate all the information and make a lengthy article.
Have a happy New Year!
60x Frankenobjectiv identification
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60x Frankenobjectiv identification
Last edited by Macro_Cosmos on Sat Dec 26, 2020 9:20 am, edited 1 time in total.
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Re: 60x Frankenobjectiv identification
Results are in. What the absolute? I cannot really comprehend this result.
Brightfield is basically unusable, it is washed out beyond belief, requires a lot of post-processing applied contrast to be usable.
RS3, CS10, CS40, and CS20, along with Ph2 and Ph2 yields some oblique illumination-like effects. This, sort of makes sense I guess? It's just the rings doing their business.
Then we have Ph1, which is the phase contrast annulus designed for 10x objectives. Inspection with a phase telescope allowed me to centre the U-PCD condenser. The smaller circle of the annulus aligns perfectly with the objective's annulus (~2.7mm). However, the objective's annulus is considerably thicker, with a greater outer diameter. Phase contrast does work nicely, and the background is black. This is very different to phase contrast objectives marked with "U" for universal. This 60x's BF is unusable. This is an example of "negative phase contrast" (I think).
https://www.olympus-lifescience.com/en/ ... ast/phase/Now, when the direct undeviated light and the diffracted light proceed to the image plane, they are 1/2 wavelength out of phase with each other. The diffracted and direct light can now interfere destructively so that the details of the specimen appear dark against a lighter background (just as they do for an absorbing or amplitude specimen). This is a description of what takes place in positive or dark phase contrast.
If the ring phase-shifter area of the phase plate were to be made thicker than the rest of the plate, direct light is slowed by 1/4 wavelength. In this case, the zeroth order light arrives at the image plane in step (or in phase) with the diffracted light, and constructive interference takes place. The image would appear bright on a darker background. The image appears bright on a darker background. This type of phase contrast is described as negative or bright contrast.
Did Olympus themselves ever make such a phase contrast objective? I really like the high contrast images, though this objective won't even work for brightfield.
Re: 60x Frankenobjectiv identification
This is really weird.
AFAIK resolution is limited by the aperture and the phase annulus is limiting the aperture, so what's the purpose of a high magnification oil objective with a so tiny annulus?. I can't imagine it being designed for normal microscope work.
Must be intended for an specific device which function and design escapes for me.
Reflected light phase contrast systems are rare and info about them scarce, could it be it the key? (I have no idea)
300 bucks doesn't seem a good inversion for this results although the fun of experimenting in the quest of hidden treasures could compensate up to some point
Your method for determining the objective BFP seems very interesting, could you explain it better for folks like me (math illiterate). Do you have any info source on the subject?
Where those data came from?
AFAIK resolution is limited by the aperture and the phase annulus is limiting the aperture, so what's the purpose of a high magnification oil objective with a so tiny annulus?. I can't imagine it being designed for normal microscope work.
Must be intended for an specific device which function and design escapes for me.
Reflected light phase contrast systems are rare and info about them scarce, could it be it the key? (I have no idea)
300 bucks doesn't seem a good inversion for this results although the fun of experimenting in the quest of hidden treasures could compensate up to some point
A simple method for dry objectives is shining a low wattage collimated laser through the front to project a round beam onto a piece of paper on the back, note the diameter of the beam and distance to the paper from the objective, and do it several times for different distances. Then just make a regression equation and find the distance where the diameter = 0, that's approximately the BFP location. Anyway, it's not as trivial for high power objectives. I don't know a good method.
Your method for determining the objective BFP seems very interesting, could you explain it better for folks like me (math illiterate). Do you have any info source on the subject?
Is the difference between a BFP of -25mm and -19.1mm negligible for normal use?
Where those data came from?
Pau
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Re: 60x Frankenobjectiv identification
Yeah, it's incredible actually. All 60x objectives in existence are Ph3, yet this one has a thick Ph1 annulus. Producing very interesting, non-conventional "negative" phase contrast results. The contrast is very high, but it's unusable for brightfield.Pau wrote: ↑Sat Dec 26, 2020 11:23 amThis is really weird.
AFAIK resolution is limited by the aperture and the phase annulus is limiting the aperture, so what's the purpose of a high magnification oil objective with a so tiny annulus?. I can't imagine it being designed for normal microscope work.
Must be intended for an specific device which function and design escapes for me.
Reflected light phase contrast systems are rare and info about them scarce, could it be it the key? (I have no idea)
The seller claimed it comes from a "RotaChrom Chromatograph", he has another objective listed, of the same claimed origin. I looked up this machine and wasn't able to find anything.
Yeah, $150 or $200 might have been better. I thought it would work well for brightfield too.
Here's a simple shot, 4 images stacked.
https://live.staticflickr.com/65535/507 ... c690_o.jpg
Honestly though, I can see this objective becoming an indispensable tool to image diatoms. The results aren't something we commonly see. We typically see DIC or brightfield and darkfield. Phase contrast isn't that common, let alone negative phase contrast. Alan Wood shared some information with me.
I suppose this means there's no NH, PL, or PLL for UIS/UIS2. Nikon makes rather new and exotic "apodisation" PC objectives, the phase annulus is encased by 2 more rings acting as an ND filter, which gets rid of the OOF doughnuts. Of course, none are visible in my shot because the background is black.For the BH-2, Olympus made 4 types of phase contrast objectives, Negative High (NH), Negative Medium (NM), Positive Low (PL) and Positive Low Low (PLL).
The info on BFP comes from here:Pau wrote: ↑Sat Dec 26, 2020 11:23 amYour method for determining the objective BFP seems very interesting, could you explain it better for folks like me (math illiterate). Do you have any info source on the subject?Is the difference between a BFP of -25mm and -19.1mm negligible for normal use?
Where those data came from?
https://www.researchgate.net/post/Is_th ... ctive_lens
I tried the method for low power and high power objectives. Can get a solid result that's not far from manufacture's specs for the former. Doesn't work at all for the latter.
As for the information on the BFP of UIS2 objectives, they can be seen here:
https://www.olympus-lifescience.com/en/ ... ve-finder/
You can also see my points on the BFP of UIS and UIS2 objectives by comparing Apos and fluorites of the same magnification. 10x SApo and Fl has the same BFP etc.
PLAPON60XOSC2 VS UPLXAPO60XO VS UPLSAPO60XW
UAPON40XO340-2 VS LUMPLFLN40XW VS UPLXAPO40X
It's pretty much either -19.1 or -25 when it comes to life science objectives. -25 requires an objective Normaski slider with the BFP1 lever. From the tiny icon of the objective, you can vaguely see either "UIS2" or "UIS2 and something underneath", which will say BFP1. What I don't like is lack of an archive, the website doesn't even list many fluorites anymore. They are presumably discontinued.
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Re: 60x Frankenobjectiv identification
This is very interesting. I'm glad it produces some nice images even if brightfield isn't an option. I love how crisp the DIC is in particular.
Re: 60x Frankenobjectiv identification
Interesting stuff. If this is coming out of a machine, it makes more sense that it is a dry lens instead of an immersion lens? I'm sure you have tried that, but you never know.
Might be part of a micro UV fluorescent detector in chromatography, with a quench of the direct light. Must be a micro cel if used with this high a magnification. BTW, I'm just guessing.
Best wishes, René
Might be part of a micro UV fluorescent detector in chromatography, with a quench of the direct light. Must be a micro cel if used with this high a magnification. BTW, I'm just guessing.
Best wishes, René
Re: 60x Frankenobjectiv identification
Actually found a link to a HPLC detector using Olympus 40x objectives in Geissler ea (2016) Microchip HPLC separations monitored simultaneously
by coherent anti-Stokes Raman scattering and fluorescence detection. (can be reached via booksc.org). No mention of phase contrast or apodization however.
René
by coherent anti-Stokes Raman scattering and fluorescence detection. (can be reached via booksc.org). No mention of phase contrast or apodization however.
René
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Re: 60x Frankenobjectiv identification
While it's definitely an oil immersion lens, it works alright without oil using the phase contrast technique as well. Dry lenses have different looking tips. I didn't check brightfield, but I can't imagine it being any better as brightfield wasn't usable with oil.René wrote: ↑Sat Jan 02, 2021 6:35 amInteresting stuff. If this is coming out of a machine, it makes more sense that it is a dry lens instead of an immersion lens? I'm sure you have tried that, but you never know.
Might be part of a micro UV fluorescent detector in chromatography, with a quench of the direct light. Must be a micro cel if used with this high a magnification. BTW, I'm just guessing.
Best wishes, René