oblique illumination

Here you can discuss different microscopic techniques and illumination methods, such as Brightfield, Darkfield, Phase Contrast, DIC, Oblique illumination, etc.
Message
Author
User avatar
woyjwjl
Posts: 325
Joined: Tue Jan 04, 2022 1:55 pm
Location: Wuhan, China

oblique illumination

#1 Post by woyjwjl » Thu May 19, 2022 7:15 am

2.jpg
2.jpg (69.21 KiB) Viewed 5851 times
1.jpg
1.jpg (86.9 KiB) Viewed 5851 times
http://www.alanwood.net/downloads/olymp ... ochure.pdf

Curious, why did the resolution doubling technology that was commercialized 50 years ago disappear?
Micrographers from China, thanks to the forum for providing a platform for exchange

Phill Brown
Posts: 603
Joined: Mon May 24, 2021 1:19 pm
Location: Devon UK.

Re: oblique illumination

#2 Post by Phill Brown » Thu May 19, 2022 7:56 pm

Cost.

Greg Howald
Posts: 1185
Joined: Tue Oct 20, 2020 6:44 am

Re: oblique illumination

#3 Post by Greg Howald » Thu May 19, 2022 8:41 pm

Agreed. Not cost effective to continue when easier ways to obtain oblique lighting were developed. But the condenser seems to have adjustment to control the degree of obliqueness or to change the light path. The only way I can do that is with two filters, one being able to be rotated on the C axis. Interesting and I imagine very accurate.

MichaelG.
Posts: 3976
Joined: Mon Apr 10, 2017 8:24 am
Location: North Wales

Re: oblique illumination

#4 Post by MichaelG. » Thu May 19, 2022 10:39 pm

Greg Howald wrote:
Thu May 19, 2022 8:41 pm
Agreed. Not cost effective to continue when easier ways to obtain oblique lighting were developed. But the condenser seems to have adjustment to control the degree of obliqueness or to change the light path. […]
Those Olympus units were beautifully made, both mechanically and optically

… and of course, Ernst Abbe originally intended the degree of obliqueness to be controllable.
the LOMO condenser being an example of his design:
http://www.microscopy-uk.org.uk/mag/ind ... lique.html
http://www.mikroskopfreunde-nordhessen. ... /OI-14.pdf

MichaelG.

.
P.S. __ This is worth a look:
https://www.researchgate.net/publicatio ... evaluation
Too many 'projects'

apochronaut
Posts: 6271
Joined: Fri May 15, 2015 12:15 am

Re: oblique illumination

#5 Post by apochronaut » Fri May 20, 2022 2:20 am

Oblique illumination was as common to research microscopes from the 1870's until the advent of phase microscopy as was the colour black. It was the D.I.C. of that era and when artfully mastered could be almost as good. Many of the discoveries made by 19th century diatomists and bacteriologists were made with oblque and every manufacturer of note designed fantastically precise, graduated oblique diaphragms for. their stands.

User avatar
woyjwjl
Posts: 325
Joined: Tue Jan 04, 2022 1:55 pm
Location: Wuhan, China

Re: oblique illumination

#6 Post by woyjwjl » Fri May 20, 2022 3:51 am

2.jpg
2.jpg (93.69 KiB) Viewed 5724 times
1.jpg
1.jpg (93.21 KiB) Viewed 5724 times
I'm trying to adapt it to BHS, and any suggestions will be appreciated.
Micrographers from China, thanks to the forum for providing a platform for exchange

apochronaut
Posts: 6271
Joined: Fri May 15, 2015 12:15 am

Re: oblique illumination

#7 Post by apochronaut » Fri May 20, 2022 8:21 am

This is from an AH or AH2 ? Since it is the iris section that moves in order divert the light , you csn't very well just attach a dovetail to the bottom. You will likely have to replace or adapt your dovetail condenser yoke to take a sleeve type condenser, so the condenser remains centered and the iris section is allowed to move below it. Olympus changed from a sleeve type to a dovetail, so there may be some parts in later sleeve type systems that can transition.

I am not sure what vertical measurements you are working with there but another option might be to machine or print a dovetail collar to fit over the optical section and tighten with set screws.

That has been a design on other systems. A removable dovetail ring around the optical "nose" of the condenser, so the condenser could be fitted into an older sleeve mount if required.

User avatar
woyjwjl
Posts: 325
Joined: Tue Jan 04, 2022 1:55 pm
Location: Wuhan, China

Re: oblique illumination

#8 Post by woyjwjl » Fri May 20, 2022 9:29 am

By affixing the BH2 dovetail, I have successfully used the AH Spin Tower PC Condenser on the BHS.

My concern is whether the change in fixation affects the 150° rotation of the tilted illumination field ....

I'll update the follow-up here when it arrives next week.
Micrographers from China, thanks to the forum for providing a platform for exchange

PeteM
Posts: 2982
Joined: Tue Dec 06, 2016 6:22 am
Location: N. California

Re: oblique illumination

#9 Post by PeteM » Fri May 20, 2022 4:13 pm

Both the Olympus and the Lomo oblique condensers can be fairly easily adapted to fit Leica, Nikon, and Olympus. Probably Zeiss as well, but haven't tried that.

User avatar
woyjwjl
Posts: 325
Joined: Tue Jan 04, 2022 1:55 pm
Location: Wuhan, China

Re: oblique illumination

#10 Post by woyjwjl » Tue May 24, 2022 8:05 am

PeteM wrote:
Fri May 20, 2022 4:13 pm
Both the Olympus and the Lomo oblique condensers can be fairly easily adapted to fit Leica, Nikon, and Olympus. Probably Zeiss as well, but haven't tried that.
As I expected, the top fixation was necessary to keep the optics centered.
The problem is that any top fixation method will increase the distance between the lens and the sample, how to solve it?
Attachments
1.jpg
1.jpg (99.66 KiB) Viewed 5513 times
2.jpg
2.jpg (61.91 KiB) Viewed 5513 times
Micrographers from China, thanks to the forum for providing a platform for exchange

User avatar
woyjwjl
Posts: 325
Joined: Tue Jan 04, 2022 1:55 pm
Location: Wuhan, China

Re: oblique illumination

#11 Post by woyjwjl » Tue May 24, 2022 8:07 am

I'm sure someone has tried it, and anyone's advice should be appreciated.
Attachments
3.png
3.png (68.03 KiB) Viewed 5512 times
Micrographers from China, thanks to the forum for providing a platform for exchange

apochronaut
Posts: 6271
Joined: Fri May 15, 2015 12:15 am

Re: oblique illumination

#12 Post by apochronaut » Tue May 24, 2022 11:44 am

Perhaps you should be looking at the condenser mount, not the condenser. Is there any way of increasing the travel?

Presumably that condenser neck fits older Olympus sleeve mounts. I would try to find an older sleeve type condenser yoke and adapt it to your microscope. That would remove the necessity of adapting the condenser to a dovetail mount, which by necessity can be no lower than the bottom of the condenser lens pack.

PeteM
Posts: 2982
Joined: Tue Dec 06, 2016 6:22 am
Location: N. California

Re: oblique illumination

#13 Post by PeteM » Tue May 24, 2022 7:05 pm

I've tried three approaches.

1) Attach a 37mm or so holder to the underside/inside of large dovetail carrier for the stage. Or adapt an old underside-condenser-mount stage. I did this for an Optiphot wafer scope with top and bottom illumination. That scope used a large stage screwed to the carrier rather than a big round dovetail fitting as for other Optiphots.

2) Just add a dovetail to the bottom of the condenser. This means both the oblique adjustment and the condenser centering adjustment screws need to be in play. Some good oblique effects available, though not clearly superior to stops.

3) Make a U-shaped sort of holder (much like Hoffman Modulation Contrast condensers use when fitted to Nikon or Olympus upright scopes). This will limit rotation (not enough room to swing the "U" all around). But with stage rotations, you can get pretty much what you want. My one attempt was a tight fit, both to install and operate, but usable.

apochronaut
Posts: 6271
Joined: Fri May 15, 2015 12:15 am

Re: oblique illumination

#14 Post by apochronaut » Tue May 24, 2022 7:24 pm

I don't think #2 is an option. Fixing the mobile diaphragm with the dovetail means that the way the device is built, in order to effect oblique, the achromat condenser has to go off axis. You would get something but the purpose in using an achromat aplanat would be defeated

User avatar
woyjwjl
Posts: 325
Joined: Tue Jan 04, 2022 1:55 pm
Location: Wuhan, China

Re: oblique illumination

#15 Post by woyjwjl » Wed May 25, 2022 3:29 am

PeteM wrote:
Tue May 24, 2022 7:05 pm
I've tried three approaches.
1、Theoretically possible. Compared with ah, the large dovetail on the stage of BH2 is the reason for the increase of travel.
Unfortunately, processing a bracket that supports centering and height adjustment and can be put into the stage dovetail is more expensive than replacing the rack.

2、I agree with apocronaut.The turret condenser can do much better.

3、Since you think it is difficult, I have nothing to say.
Micrographers from China, thanks to the forum for providing a platform for exchange

PeteM
Posts: 2982
Joined: Tue Dec 06, 2016 6:22 am
Location: N. California

Re: oblique illumination

#16 Post by PeteM » Wed May 25, 2022 7:44 am

The #2 option works reasonably well. It's just a bit of a kludge -- especially if you intend this for your main condenser, rather than occasional use for oiling it to a slide or oblique.

I originally added a dovetail and a flat flange above it to use the 1.4na Olympus condenser just for oil immersion (keeping it entirely usable for its original mounting). At the time it was the only 1.4na condenser I could afford - a fraction of the cost of a proper BH2 version.

However, that thin flat flange is wide enough it can rest on top of the condenser fork mount and be moved forward as much as 15mm off center. The condenser itself has about 15mm of offset that can head in the other direction. So, it's possible to put the top of the condenser lens directly in line with the objective -- and offset the bottom up to the full 15mm range of the condenser. Intermediate positions as desired and the iris still functional.

Just as you want with oblique, the images are much sharper. It's reasonably easy to adjust, but depends upon (fairly dependable) gravity and a sliding fit into the dovetail fork to stay put.

If only 5mm or so offsets are wanted, then the dovetail can be locked in place slightly forward and offset and the fork adjustments used for further offset. Top lens on axis and the iris preset. This might be preferred for something like focus stacking where you're worried about the condenser getting jarred out of alignment.

Stage rotations are used to change the direction of oblique relative to the specimen.

If you intend this condenser to be in use almost all the time, then I'd agree you might want to put a dovetail around the collar and swap in a modified condenser rack to support it. More trouble, though, to swap racks should you mostly want to use BHS era dovetail mount condensers that support the wider field of low power objectives (flip top condenser?), phase contrast, or DIC.
.
.
Condenser offset in mount.jpg
Condenser offset in mount.jpg (115.26 KiB) Viewed 5386 times

User avatar
woyjwjl
Posts: 325
Joined: Tue Jan 04, 2022 1:55 pm
Location: Wuhan, China

Re: oblique illumination

#17 Post by woyjwjl » Wed May 25, 2022 2:43 pm

You probably didn't understand what we said about the trip ....
4.jpg
4.jpg (94.19 KiB) Viewed 5320 times
3.jpg
3.jpg (79.83 KiB) Viewed 5332 times
2.jpg
2.jpg (80.58 KiB) Viewed 5332 times
AH No stage big dovetail
AH No stage big dovetail
1.jpg (82.26 KiB) Viewed 5332 times
From your photos it is obviously Nikon, did you indeed try it on the Olympus BH2?

PS, what I meant by "better" was: rotating the phase contrast turret condenser to produce the tilted illumination.
Micrographers from China, thanks to the forum for providing a platform for exchange

PeteM
Posts: 2982
Joined: Tue Dec 06, 2016 6:22 am
Location: N. California

Re: oblique illumination

#18 Post by PeteM » Wed May 25, 2022 3:50 pm

it works the same way on a BHS. The condenser rests on the fork. The top lens can be centered directly on axis with the objectives. The bottom part can offset to the front the full 15mm travel of the oblique condenser. It's about as stable as a book resting on a table - or more like a book in a bookshelf since the fork constrains it somewhat laterally.

You're right - I don't understand what you mean by the "trip." For both Nikon and Olympus, the condenser can be inserted easily and the top lens will travel all the way to the bottom of a slide. X-y stage movements work fine. Kohler illumination works fine.

I did understand what you meant about rotating a phase or darkfield annulus to get oblique - and as said earlier this method isn't better than stops -- assuming your phase condenser also has a 1.4na lens. If you already have something like a 1.3 or 1.4 na phase or DIC condenser, there's no need to adapt this.

Here's a BHS stand taken out to show the fit and answer your question - is it possible to adapt one of these old condensers to a newer stand? This is one of the three ways tried and works reasonably well for occasional oblique or 1.4 na oiled use.
.
.
Offset_condenser-BHS.jpg
Offset_condenser-BHS.jpg (70.38 KiB) Viewed 5311 times

apochronaut
Posts: 6271
Joined: Fri May 15, 2015 12:15 am

Re: oblique illumination

#19 Post by apochronaut » Wed May 25, 2022 4:17 pm

Very odd adaption Pete. You move the oblique diaphram first, then decenter the condenser against it to center it to the objective? And the whole thing just sits on a flat surface?

PeteM
Posts: 2982
Joined: Tue Dec 06, 2016 6:22 am
Location: N. California

Re: oblique illumination

#20 Post by PeteM » Wed May 25, 2022 4:19 pm

Probably worth adding, if anyone wants to machine or print a dovetail to fit either or both Nikon and Olympus - the Nikon condenser dovetail is about 0.5mm smaller. It fits Olympus just fine, clamps firmly in place, and the Olympus centering adjustments easily take up any slack. Most OEM Olympus condenser dovetails are just a bit too large to fit the Nikon fork.

Optically, they're cross-compatible in terms of adjusting for Kohler illumination.

PeteM
Posts: 2982
Joined: Tue Dec 06, 2016 6:22 am
Location: N. California

Re: oblique illumination

#21 Post by PeteM » Wed May 25, 2022 4:25 pm

apochronaut wrote:
Wed May 25, 2022 4:17 pm
Very odd adaption Pete. You move the oblique diaphram first, then decenter the condenser against it to center it to the objective? And the whole thing just sits on a flat surface?
As said, Phil, it's a kludge. Vertical support is the flat surface. It's locked reasonably well side to side by the fork.

Works surprisingly well, though, if one just wants to have a 1.4na condenser for occasional oblique use. Swapping it in and getting it adjusted for a given specimen is a matter of seconds. The reward is that much crisper oblique image.

Also useful to if you want to have a 1.4 na condenser that can be oiled to the bottom of a slide and pay more like $80 than $350 for it. In that case everything can be locked in place, with no offset.

It can also be locked in place with slight offsets (say up to 5mm) as described before.

User avatar
woyjwjl
Posts: 325
Joined: Tue Jan 04, 2022 1:55 pm
Location: Wuhan, China

Re: oblique illumination

#22 Post by woyjwjl » Thu May 26, 2022 1:24 am

According to my understanding, perfect tilt lighting should support simultaneous adjustment: aperture size, occlusion range and occlusion angle. And does not affect Kohler lighting.

This is the original design intention of ah-aac, which cannot be fully achieved by the turret condenser.

In order to achieve this function, it must be fixed at the top, which leads to the "trip" problem on the BHS.
AH.jpg
AH.jpg (184.39 KiB) Viewed 5230 times
I even want to install the whole bracket on the BHS. Has anyone tried?
Micrographers from China, thanks to the forum for providing a platform for exchange

User avatar
woyjwjl
Posts: 325
Joined: Tue Jan 04, 2022 1:55 pm
Location: Wuhan, China

Re: oblique illumination

#23 Post by woyjwjl » Thu May 26, 2022 1:50 am

Is it more realistic to install this?
Attachments
1.jpg
1.jpg (57.14 KiB) Viewed 5222 times
Micrographers from China, thanks to the forum for providing a platform for exchange

apochronaut
Posts: 6271
Joined: Fri May 15, 2015 12:15 am

Re: oblique illumination

#24 Post by apochronaut » Thu May 26, 2022 2:29 am

In my opinion the only way you are going to have a fully functional and fluid oblique system is to find a way to fix the condenser rigidly centered and allow the secondary oblique diaphragm section to move against it. If that involves translating an entire disused stage section over then so be it but possibly retrifitting the condenser carrier to receive a sleeve type condenser with increased travel to the stage might be the best option.

viktor j nilsson
Posts: 760
Joined: Thu Aug 23, 2018 10:12 pm
Location: Lund, Sweden

Re: oblique illumination

#25 Post by viktor j nilsson » Thu May 26, 2022 5:18 am

To me, the U-shaped wrap around solution seems like the only viable option:

Image

If I were you, I'd draw it up in Fusion 360 and 3D print it. If that doesn't turn out sufficiently rigid and properly aligned, it would probably need to be machined on a mill.

But I think the chances are pretty good it could work well enough if printed on a well calibrated printer.

User avatar
woyjwjl
Posts: 325
Joined: Tue Jan 04, 2022 1:55 pm
Location: Wuhan, China

Re: oblique illumination

#26 Post by woyjwjl » Thu May 26, 2022 8:02 am

I agree with your idea. The sketch is as follows and needs polishing. I will update it later
Attachments
1.png
1.png (49.49 KiB) Viewed 5172 times
Micrographers from China, thanks to the forum for providing a platform for exchange

viktor j nilsson
Posts: 760
Joined: Thu Aug 23, 2018 10:12 pm
Location: Lund, Sweden

Re: oblique illumination

#27 Post by viktor j nilsson » Thu May 26, 2022 8:54 am

Looks good!

User avatar
woyjwjl
Posts: 325
Joined: Tue Jan 04, 2022 1:55 pm
Location: Wuhan, China

Re: oblique illumination

#28 Post by woyjwjl » Tue May 31, 2022 8:31 am

condenser 3D.png
condenser 3D.png (28.8 KiB) Viewed 5061 times

Update the progress
interferes .jpg
interferes .jpg (90.57 KiB) Viewed 5061 times
It interferes with the swallow tail of the stage. It is estimated that it has to be transformed
Micrographers from China, thanks to the forum for providing a platform for exchange

PeteM
Posts: 2982
Joined: Tue Dec 06, 2016 6:22 am
Location: N. California

Re: oblique illumination

#29 Post by PeteM » Tue May 31, 2022 4:22 pm

As mentioned earlier, the Hoffman Modulation Contrast condensers for upright Nikon and Olympus scopes use a similar U-shaped bracket. What they do to make it easier to insert the condenser under the fork and dovetail is split the sideways U in half with a dovetail connection.
.
.
Hoffman condenser.jpg
Hoffman condenser.jpg (59.88 KiB) Viewed 4987 times

User avatar
woyjwjl
Posts: 325
Joined: Tue Jan 04, 2022 1:55 pm
Location: Wuhan, China

Re: oblique illumination

#30 Post by woyjwjl » Wed Jun 01, 2022 1:06 am

First, these are two different options for increasing contrast illumination, and the "Hoffman Modulation Contrast Microscopy" requires a special objective lens(ORC). So-called:"The new rabbit hole".
2.png
2.png (245.58 KiB) Viewed 4957 times
Second, I don't think the "split in half" is for ease of installation, it's just for height adjustment.

Finally, as I said at the beginning, the biggest difficulty in fixing the bottom for "Oblique or Anaxial Illumination" is the stage dovetail.

Please correct me if I am wrong.
Micrographers from China, thanks to the forum for providing a platform for exchange

Post Reply