DIY Epi Illuminator

Here you can discuss different microscopic techniques and illumination methods, such as Brightfield, Darkfield, Phase Contrast, DIC, Oblique illumination, etc.
Post Reply
Message
Author
LouiseScot
Posts: 1167
Joined: Tue Jul 07, 2020 1:51 pm
Location: Scotland

DIY Epi Illuminator

#1 Post by LouiseScot » Thu Oct 27, 2022 5:46 pm

Hi all

I've been working on an epi/illuminator and the basic thing is ok. But I want to add field lens(es) and field aperture. I'm wondering if anyone out there has any insight on how to do the design and calculate the focal length of said lens(es) and what kind of lens(es) are best, bearing in mind I'm using infinity optics. Unfortunately, I always seem to have a blind spot when it comes to figuring out focal lengths/lens types etc. There must be a simple and easy explanation that would help! I'm presuming an infinity lens would be expecting an approximately parallel beam of light entering its 'exit pupil' though I'm not 100% sure on that or how critical it might be!
If anyone has any insights on (infinity optics) epi/vertical illuminator design I'm eager for guidance and suggestions :)

Much gratitude in advance

Louise
A Nikon CF plan 20x; A Swift 380T; A DIY infinity corrected focus rail system with a 40x/0.65 Olympus Plan, a 10x/0.30 Amscope Plan Fluor, and a 20x/0.75 Nikon Plan Apo

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

Re: DIY Epi Illuminator

#2 Post by MichaelG. » Thu Oct 27, 2022 6:29 pm

May I refer you to this, Louse :
viewtopic.php?f=28&t=9722&hilit=ball+lens

It looks, to me, like an excellent starting point [at least for the lower magnifications]

For high magnifications, true co-axial illumination [via the objective] is probably preferable.

MichaelG.
Too many 'projects'

BramHuntingNematodes
Posts: 1538
Joined: Tue Jan 21, 2020 1:29 am
Location: Georgia, USA

Re: DIY Epi Illuminator

#3 Post by BramHuntingNematodes » Thu Oct 27, 2022 6:51 pm

Thorlabs sells some nice aspheric lenses for pretty cheap for this kind of thing that I have had success with. They even have the option of grinding one side of you want diffusion
1942 Bausch and Lomb Series T Dynoptic, Custom Illumination

LouiseScot
Posts: 1167
Joined: Tue Jul 07, 2020 1:51 pm
Location: Scotland

Re: DIY Epi Illuminator

#4 Post by LouiseScot » Thu Oct 27, 2022 7:19 pm

MichaelG. wrote:
Thu Oct 27, 2022 6:29 pm
May I refer you to this, Louse :
viewtopic.php?f=28&t=9722&hilit=ball+lens

It looks, to me, like an excellent starting point [at least for the lower magnifications]

For high magnifications, true co-axial illumination [via the objective] is probably preferable.

MichaelG.
Thanks, but it's a coaxial system I'm working on.

Louise
A Nikon CF plan 20x; A Swift 380T; A DIY infinity corrected focus rail system with a 40x/0.65 Olympus Plan, a 10x/0.30 Amscope Plan Fluor, and a 20x/0.75 Nikon Plan Apo

LouiseScot
Posts: 1167
Joined: Tue Jul 07, 2020 1:51 pm
Location: Scotland

Re: DIY Epi Illuminator

#5 Post by LouiseScot » Thu Oct 27, 2022 7:36 pm

BramHuntingNematodes wrote:
Thu Oct 27, 2022 6:51 pm
Thorlabs sells some nice aspheric lenses for pretty cheap for this kind of thing that I have had success with. They even have the option of grinding one side of you want diffusion
Using this Zeiss diagram below as an example, you can see there is a lens that is between the field diaphragm and the objective. It looks to be about equidistant suggesting it has a fl of about 82.5mm but that's a bit of a guesstimate on my part (half the tube lens focal length). If anyone with a knowledge of optics can explain how I would calculate it, that would be very helpful.


Zeiss_ReflectedDiag.JPG
Zeiss_ReflectedDiag.JPG (50.74 KiB) Viewed 3987 times

Thanks

Louise
A Nikon CF plan 20x; A Swift 380T; A DIY infinity corrected focus rail system with a 40x/0.65 Olympus Plan, a 10x/0.30 Amscope Plan Fluor, and a 20x/0.75 Nikon Plan Apo

BramHuntingNematodes
Posts: 1538
Joined: Tue Jan 21, 2020 1:29 am
Location: Georgia, USA

Re: DIY Epi Illuminator

#6 Post by BramHuntingNematodes » Fri Oct 28, 2022 4:32 am

I'm not exactly sure how to interpret this four ray ray tracing diagram.
1942 Bausch and Lomb Series T Dynoptic, Custom Illumination

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

Re: DIY Epi Illuminator

#7 Post by MichaelG. » Fri Oct 28, 2022 6:45 am

BramHuntingNematodes wrote:
Fri Oct 28, 2022 4:32 am
I'm not exactly sure how to interpret this four ray ray tracing diagram.
.

You are not alone, Bram … but my interpretation is that it starts at the lamp with two point-sources that represent the upper and lower extremes of the filament.
The infinite number of other points all, obviously, lie between those two.

MichaelG.
Too many 'projects'

LouiseScot
Posts: 1167
Joined: Tue Jul 07, 2020 1:51 pm
Location: Scotland

Re: DIY Epi Illuminator

#8 Post by LouiseScot » Fri Oct 28, 2022 8:20 am

I may have solved it! If I'm right, the lens has to be exactly 1 focal length away from the object (field diaphragm) and should then produce a collimated beam to the beamsplitter and down to the objective lens. The objective itself should then create an image of the field iris at the specimen plane. That way it would be independent of which objective is being used since the beam is focused on infinity until it reaches the objective lens.
I hope I'm right! I'll try it out today :)

Louise
A Nikon CF plan 20x; A Swift 380T; A DIY infinity corrected focus rail system with a 40x/0.65 Olympus Plan, a 10x/0.30 Amscope Plan Fluor, and a 20x/0.75 Nikon Plan Apo

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

Re: DIY Epi Illuminator

#9 Post by MichaelG. » Fri Oct 28, 2022 9:05 am

I hope you’re right too, Louise … it would make life easy … but frankly, I doubt it

It seems pretty clear, from the fuzzy illustration, that the beam is converging en route to the objective

MichaelG.
Too many 'projects'

LouiseScot
Posts: 1167
Joined: Tue Jul 07, 2020 1:51 pm
Location: Scotland

Re: DIY Epi Illuminator

#10 Post by LouiseScot » Fri Oct 28, 2022 9:53 am

MichaelG. wrote:
Fri Oct 28, 2022 9:05 am
I hope you’re right too, Louise … it would make life easy … but frankly, I doubt it

It seems pretty clear, from the fuzzy illustration, that the beam is converging en route to the objective

MichaelG.
Hiya

It does appear to show that, but diagrams don't necessarily reflect reality. However, an experiment should confirm what works. Using the thin lens formula, if a lens with a focal length of 50mm was placed at 70mm from the object, an image would focus at 175mm rather than infinity. But, going the other way, an outgoing beam from an infinity lens should be approximately collimated until it reaches the tube lens (?) though the diagram seems to show the beam expanding. It may not need for the object - lens distance to be exactly 1 focal length. So, for an f=50mm lens and the object at 71.74mm, the image distance would be 165mm ie the same as the Zeiss tube lens nominal focal length. A few experiments should demonstrate what works best. A quick test with a 4x infinity objective and a torch, shows that, with the objective focused, the exiting beam actually does diverge somewhat. Is this a lens property or an effect of the objective exit pupil (which, presumably acts as a secondary source?). Or, perhaps, there is simply an engineering solution component, or the beam is allowed to diverge somewhat to get the optimum aperture from the tube lens? I wish I had/knew all the answers!

Thanks

Louise
A Nikon CF plan 20x; A Swift 380T; A DIY infinity corrected focus rail system with a 40x/0.65 Olympus Plan, a 10x/0.30 Amscope Plan Fluor, and a 20x/0.75 Nikon Plan Apo

LouiseScot
Posts: 1167
Joined: Tue Jul 07, 2020 1:51 pm
Location: Scotland

Re: DIY Epi Illuminator

#11 Post by LouiseScot » Fri Oct 28, 2022 3:08 pm

Well, I think I just demonstrated earlier that the lens formula works :)
Using a biconvex lens with f=51 I get a beam which is focused on infinity at an object distance of 1f. I can then focus the beam with the 4x infinity objective at any reasonable distance from the lens. If I move the lens further away from the object it will form a focused image without the objective. However, even at f=1 the beam does diverge even though it's focused on infinity. I think maybe I need to choose a lens which restricts the width of the beam between it and the objective. Also an achromat would be better.

Having rummaged around, I found 2-4 achromats I could maybe use: 1 with d= 30mm, f=60-65mm, 1 with d=26.5, f= 59, and 2 with d=37.5, f= 100.
It intuitively feels to me that larger diameter would be better? The 30mm lens looks promising. The 37.5mm lenses could be combined to give an overall f=50mm but might be a bit weighty... On the other hand, using a 37.5mm lens at f= 100mm results in a smaller circle of light at the objective distance - which seems desirable. Has anyone ever looked inside an epi/vertical illuminator and seen the lenses?

Thanks

Louise
A Nikon CF plan 20x; A Swift 380T; A DIY infinity corrected focus rail system with a 40x/0.65 Olympus Plan, a 10x/0.30 Amscope Plan Fluor, and a 20x/0.75 Nikon Plan Apo

GerryR
Posts: 183
Joined: Sun May 22, 2022 11:44 am
Location: Virginia, USA

Re: DIY Epi Illuminator

#12 Post by GerryR » Fri Oct 28, 2022 5:02 pm

I can't be much help in the optics department, but just wanted to say that I enjoy watching how you tackle a problem. You are tenacious; very inspiring!!

LouiseScot
Posts: 1167
Joined: Tue Jul 07, 2020 1:51 pm
Location: Scotland

Re: DIY Epi Illuminator

#13 Post by LouiseScot » Fri Oct 28, 2022 5:09 pm

GerryR wrote:
Fri Oct 28, 2022 5:02 pm
I can't be much help in the optics department, but just wanted to say that I enjoy watching how you tackle a problem. You are tenacious; very inspiring!!
Well, um, thanks. I wouldn't call myself 'tenacious' - I'm just trying to make a useful add-on. I do find that if I get stuck and post the problem on the forum, the act of doing that helps me think of solutions even if I don't get any/many useful responses.

Louise
A Nikon CF plan 20x; A Swift 380T; A DIY infinity corrected focus rail system with a 40x/0.65 Olympus Plan, a 10x/0.30 Amscope Plan Fluor, and a 20x/0.75 Nikon Plan Apo

BramHuntingNematodes
Posts: 1538
Joined: Tue Jan 21, 2020 1:29 am
Location: Georgia, USA

Re: DIY Epi Illuminator

#14 Post by BramHuntingNematodes » Fri Oct 28, 2022 8:02 pm

LouiseScot wrote:
Fri Oct 28, 2022 3:08 pm
anyone ever looked inside an epi/vertical illuminator and seen the lenses?

Thanks

Louise
The microzoom has only a single collimating lens for.the illuminator. The coaxial illuminator for the sz7 has one lens per eye, in addition to the polarizers.
1942 Bausch and Lomb Series T Dynoptic, Custom Illumination

LouiseScot
Posts: 1167
Joined: Tue Jul 07, 2020 1:51 pm
Location: Scotland

Re: DIY Epi Illuminator

#15 Post by LouiseScot » Fri Oct 28, 2022 8:26 pm

BramHuntingNematodes wrote:
Fri Oct 28, 2022 8:02 pm
LouiseScot wrote:
Fri Oct 28, 2022 3:08 pm
anyone ever looked inside an epi/vertical illuminator and seen the lenses?

Thanks

Louise
The microzoom has only a single collimating lens for.the illuminator. The coaxial illuminator for the sz7 has one lens per eye, in addition to the polarizers.
Thanks, though I don't know the instruments you mention. I suppose I really need info on something similar to the Zeiss (as pictured above) or equivalent Nikon/Olympus. I plan to also add a polarizer and also want to see if I can use it with the reflected DIC nosepiece - if possible! I'm using that nosepiece anyway but not yet tried the reflected DIC. Anyway, I was hoping to find out a typical field lens diameter. But if nobody knows I'll just try and see!

Louise
A Nikon CF plan 20x; A Swift 380T; A DIY infinity corrected focus rail system with a 40x/0.65 Olympus Plan, a 10x/0.30 Amscope Plan Fluor, and a 20x/0.75 Nikon Plan Apo

Chas
Posts: 422
Joined: Tue Jan 19, 2021 3:11 pm

Re: DIY Epi Illuminator

#16 Post by Chas » Sat Oct 29, 2022 4:07 pm

The older (finite) illuminators that were placed directly above the revolving nosepiece or changer have quite a small lens, around 1 cm diameter.
In that era they all seem to have a diffuser disk as the first item next to the bulb. If this falls out the image that you see through the eyepiece can be dominated by the structure of the light source, so maybe putting a diffuser in front of your LED torch might be worth a try?
CTS illuminator.jpg
CTS illuminator.jpg (70.2 KiB) Viewed 3761 times
I also have one Beck Epimax illuminator that mounts further away from the nosepiece and the lens in that is a little larger ..so perhaps the closer the illuminator is to the objective, the smaller the lens(?).

If the Iris and lens tube assembly is completely removed from the CTS illuminator it is quite possible to get a reasonable illumination from a diffuse light with a fixed stop (ie something black with a hole in it ) held a few inches away from the window next to angled reflector.

Edit: You also need somewhere to dump the light... I would suggest a hole :-) In the CTS, above, it is a frosted and smoked glass window on the opposite side to the incoming, illuminating, light.

LouiseScot
Posts: 1167
Joined: Tue Jul 07, 2020 1:51 pm
Location: Scotland

Re: DIY Epi Illuminator

#17 Post by LouiseScot » Sat Oct 29, 2022 4:43 pm

Chas wrote:
Sat Oct 29, 2022 4:07 pm
The older (finite) illuminators that were placed directly above the revolving nosepiece or changer have quite a small lens, around 1 cm diameter.
In that era they all seem to have a diffuser disk as the first item next to the bulb. If this falls out the image that you see through the eyepiece can be dominated by the structure of the light source, so maybe putting a diffuser in front of your LED torch might be worth a try?
CTS illuminator.jpg

I also have one Beck Epimax illuminator that mounts further away from the nosepiece and the lens in that is a little larger ..so perhaps the closer the illuminator is to the objective, the smaller the lens(?).

If the Iris and lens tube assembly is completely removed from the CTS illuminator it is quite possible to get a reasonable illumination from a diffuse light with a fixed stop (ie something black with a hole in it ) held a few inches away from the window next to angled reflector.
Hi

Thanks and wow, that's an antique diagram! I've decided to go for the 37.5mm achromat (I think it won't be too small!) and I'm aiming for Kohler Illumination and with a polarizer option, and maybe also reflected DIC later. I'm just trying to build the front section with the lens and field diaphragm today. If that goes to plan, I'll add the aperture diaphragm and LED illuminator. Those will probably have to wait until next week.
Thanks for taking the trouble - much appreciated!

Louise
A Nikon CF plan 20x; A Swift 380T; A DIY infinity corrected focus rail system with a 40x/0.65 Olympus Plan, a 10x/0.30 Amscope Plan Fluor, and a 20x/0.75 Nikon Plan Apo

User avatar
blekenbleu
Posts: 300
Joined: Tue Feb 25, 2020 5:55 pm
Location: South Carolina low country
Contact:

Re: DIY Epi Illuminator

#18 Post by blekenbleu » Sat Oct 29, 2022 7:30 pm

A coaxial system will want a uniformly illuminated circle of at least the diameter of epi objectives' outer sleeves,
which should be sharply focused by the aperture diaphragm, while the field diaphragm should be sharply focused by objectives
on the stage. For infinity objectives, that has the field lens focal length = distance from that lens to the field diaphragm.
Given that focal length, the aperture diaphragm wants placing according to a finite system using that field lens
and its distance to objective's back focus plane. Magnification for that finite system and the objective outer diameter
determines the required aperture diaphragm diameter.

FWIW, Nikon had 2 quite different epi illuminator designs for Labophot/Optiphot era microscopes,
with largest lens in one no more than 25mm; it also has a lens between field and aperture diaphragms, e.g.
Image
That lens between field and aperture diaphragms
evidently concentrates outer rays from lamp image to center point of half mirror.
https://www.olympus-lifescience.com/en/ ... ectkohler/
Last edited by blekenbleu on Sat Oct 29, 2022 8:07 pm, edited 4 times in total.
Metaphot, Optiphot 1, 66; AO 10, 120, EPIStar, Cycloptic

LouiseScot
Posts: 1167
Joined: Tue Jul 07, 2020 1:51 pm
Location: Scotland

Re: DIY Epi Illuminator

#19 Post by LouiseScot » Sat Oct 29, 2022 7:41 pm

blekenbleu wrote:
Sat Oct 29, 2022 7:30 pm
A coaxial system will want a uniformly illuminated circle of at least the diameter of epi objectives' outer sleeves,
which should be sharply focused by the aperture diaphragm, while the field diaphragm should be sharply focused by objectives
on the stage. For infinity objectives, that has the field lens focal length = distance from that lens to the field diaphragm.
Given that focal length, the aperture diaphragm wants placing according to a finite system using that field lens
and its distance to objective's back focus plane. Magnification for that finite system and the objective outer diameter
determines the required aperture diaphragm diameter.

FWIW, Nikon had 2 quite different epi illuminator designs for Labophot/Optiphot era microscopes,
with largest lens in one no more than 25mm; it also has a lens between field and aperture diaphragms.
Hi

Thanks - though I'd figured that out. See #11 above viewtopic.php?p=128422#p128422
I'm in the process of constructing my design, but earlier, to my dismay, my downgraded Fusion 360 (from educational to personal) no longer allows custom threads, amongst other things. So, a bit of a setback but I can work around it - I think! Am debating with myself whether to fork out the $409 for a paid version...

Louise
A Nikon CF plan 20x; A Swift 380T; A DIY infinity corrected focus rail system with a 40x/0.65 Olympus Plan, a 10x/0.30 Amscope Plan Fluor, and a 20x/0.75 Nikon Plan Apo

Scarodactyl
Posts: 2775
Joined: Sat Mar 03, 2018 9:09 pm

Re: DIY Epi Illuminator

#20 Post by Scarodactyl » Sun Oct 30, 2022 5:19 am

You can directly edit the sql files to make custom threads.

LouiseScot
Posts: 1167
Joined: Tue Jul 07, 2020 1:51 pm
Location: Scotland

Re: DIY Epi Illuminator

#21 Post by LouiseScot » Sun Oct 30, 2022 9:28 am

Scarodactyl wrote:
Sun Oct 30, 2022 5:19 am
You can directly edit the sql files to make custom threads.
Hiya - I think you mean the .xml files. Yes, I used to do that with the educational version but the files are no longer available with the personal one. Since I use a number of astronomy-linked threads and other non-standard ones, it's a pain and time-consuming to mess about trying to figure out ways around it, I'm thinking of buying a one-year licence. I've tried using scaling in the slicer but it's not practical to do that for most parts. Oh well.

Thanks anyway

Louise
A Nikon CF plan 20x; A Swift 380T; A DIY infinity corrected focus rail system with a 40x/0.65 Olympus Plan, a 10x/0.30 Amscope Plan Fluor, and a 20x/0.75 Nikon Plan Apo

Scarodactyl
Posts: 2775
Joined: Sat Mar 03, 2018 9:09 pm

Re: DIY Epi Illuminator

#22 Post by Scarodactyl » Sun Oct 30, 2022 4:09 pm

Ohbyeha I mean xml. I've been editing them semi-recently, didn't notice any changes.

LouiseScot
Posts: 1167
Joined: Tue Jul 07, 2020 1:51 pm
Location: Scotland

Re: DIY Epi Illuminator

#23 Post by LouiseScot » Sun Oct 30, 2022 4:13 pm

Scarodactyl wrote:
Sun Oct 30, 2022 4:09 pm
Ohbyeha I mean xml. I've been editing them semi-recently, didn't notice any changes.
Which edition do you have?
A Nikon CF plan 20x; A Swift 380T; A DIY infinity corrected focus rail system with a 40x/0.65 Olympus Plan, a 10x/0.30 Amscope Plan Fluor, and a 20x/0.75 Nikon Plan Apo

LouiseScot
Posts: 1167
Joined: Tue Jul 07, 2020 1:51 pm
Location: Scotland

Re: DIY Epi Illuminator

#24 Post by LouiseScot » Sun Oct 30, 2022 5:52 pm

Scarodactyl wrote:
Sun Oct 30, 2022 4:09 pm
Ohbyeha I mean xml. I've been editing them semi-recently, didn't notice any changes.
Ahhh, after all that it looks like I'd been making a rookie error with my folder navigation - seems to be up and running again now!

Louise
A Nikon CF plan 20x; A Swift 380T; A DIY infinity corrected focus rail system with a 40x/0.65 Olympus Plan, a 10x/0.30 Amscope Plan Fluor, and a 20x/0.75 Nikon Plan Apo

Scarodactyl
Posts: 2775
Joined: Sat Mar 03, 2018 9:09 pm

Re: DIY Epi Illuminator

#25 Post by Scarodactyl » Sun Oct 30, 2022 10:46 pm

The folder moves every time it updates, which is annoying.

LouiseScot
Posts: 1167
Joined: Tue Jul 07, 2020 1:51 pm
Location: Scotland

Re: DIY Epi Illuminator

#26 Post by LouiseScot » Sun Oct 30, 2022 11:03 pm

Scarodactyl wrote:
Sun Oct 30, 2022 10:46 pm
The folder moves every time it updates, which is annoying.
There's a free add-on called ThreadKeeper which I've downloaded and installed but not set up yet

https://apps.autodesk.com/FUSION/en/Det ... n&os=Win64

Louise
A Nikon CF plan 20x; A Swift 380T; A DIY infinity corrected focus rail system with a 40x/0.65 Olympus Plan, a 10x/0.30 Amscope Plan Fluor, and a 20x/0.75 Nikon Plan Apo

Post Reply