Darkfield through glass edge illumination - Coleps

[Chainsaw_DNA]

Experimenting using a single power LED illuminating the front edge of the glass slide.
Very pleased with the results. Some images look just like darkfield. The ones in this video were in murky waters, which make the images look absolutely 3 dimensional.

Not sure if this can really be called darkfield, but thought I'd share the results of such an easy illumination technique.

https://www.youtube.com/watch?v=_ScxA1wcDUc

Does anyone know what is that round blob that the 2 Coleps are trying to consume (bright field footage)?.

Thanks

[Shivs]

Very cool, I like the production I like to add music and effects to videos also

[Sven]

Very nice results! Can you show how you made the dark field lighting?

[Hobbyst46]

Hi, welcome.
I liked your Video, especially the cast shadow.
You might find this old post of interest
https://www.microbehunter.com/microscop ... o&start=30

[DonSchaeffer]

Congratulations! I use this method too. You can get a very nice effect by combining under-stage light with sidelight. It's particularly good at high power. I use two flashlights hitting the slide a slightly different sideways angles plus the under-stage light--carefully controlling intensity. The condenser increases depth of field. It's particularly good for bringing out small details like bacteria. You can buy a condenser on EBay or Amazon for a few dollars. When I had my first microscope, i bought one and glued it in place. What model do you have?

[Chainsaw_DNA]

Thanks, Sven! I'll work on a video with the details, but here are the simple basics:

• 1 high power (5W) white LED.

• 1 DC power supply capable of easily varying the output voltage.

• 1 heat sink (highly recommended). This is in addition to the star heatsink that already comes with the LED.

The power supply should be able to easily adjust it's output voltage.
Caution to not exceed the maximum rating of the LED. For 5W LEDs, that is typically 0.7 Amps. I never go above 0.6 Ams. Preferably, get a power supply where you can set the maximum output current, like the one in the picture.
No heatskink is needed if you are not making the LED too bright. If you can't touch the LED's star heatsink, then it's too hot and you need the extra heatsink (highly recommended)

[PeteM]

Liked your videos.

Have you tried this with something else beside pond critters? I'm wondering if the drop of water and coverslip act (along with the slide) as somewhat of a light pipe? If it also works with things like smears and dry mount slides, that could be doubly cool.

[Sven]

Thanks for the images! Very interresting. I would have expected that the light only should have iluminated the slide, like the link provided by hobbyst46. Cool.that this also works!

[elwaine]

Fascinating. Got to give it a try. Wonderful video. Thanks for sharing!

[Greg Howald]

That's a piece of great work and ingenuity!
Greg

[LouiseScot]

Interesting! I'll have to try that!
I made some similar power LED setups for my my 380T but to use with the darkfield condenser:

10W and 3W LEDs.jpg (54.78 KiB) Viewed 6909 times

Top one is a 10W LED on an aluminium bar, bottom a 3W just on a heatsink. Plus a variable psu though the LEDs are controlled by the constant current buck converters.

Louise





























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[LouiseScot]

Does anyone know what is that round blob that the 2 Coleps are trying to consume (bright field footage)?.

Thanks

I think it's probably an encysted ciliate/protozoan - unless someone else knows different?

Louise

[Chainsaw_DNA]

Very cool, I like the production I like to add music and effects to videos also

Thanks, Shivs!

[Chainsaw_DNA]

Hi, welcome.
I liked your Video, especially the cast shadow.
You might find this old post of interest
https://www.microbehunter.com/microscop ... o&start=30

Hi Hobbyst46. Thank you for the welcome and for the very interesting post on the work that you and others have done on edge illumination.
Have you heard of anyone experimenting with a laser beam that quickly sweeps the slide's edge?

[Hobbyst46]

...Have you heard of anyone experimenting with a laser beam that quickly sweeps the slide's edge?

Alas, no. Furthermore, I did not see many followers of Kawano's article about edge illumination. Perhaps MichaelG noticed progress in that direction.
The challenge in that type of illumination, I guess, is limitation of the light beam to the internals of the slide; total internal reflection, to create a true black background at high NA.

[zzffnn]

For those edge illumination darkfield, has any of you examined objective back focal plane to make sure objective aperture is sufficiently illuminated by peripheral circular light?

I apologize if I sound discouraging or harsh.

Some of the higher NA (0.65 and above) images presented here look as if objective aperture was not fully utilized.

A dedicated oil immersion darkfield condenser may be easily adapted to your microscope and provide even better darkfield images.

I am not seeing evidence than LED edge illumination would work better herein, unless edge illumination is evenly distributed and very carefully executed (which would be a more difficult task than simply adapting a real darkfield condenser, assuming your end goal is better images and not DIY fun). I did try LED edge illumination before, but in my hands it didn't work that well above NA 0.4 (20x objective); at NA 0.25 and 10x, it is very easy to get DIY dakrfield with a coin or a dark background + side lighting.

[Saul]

https://www.microbehunter.com/microscop ... =28&t=9895

[zzffnn]

Saul, you bera version looks very promising, have you tested it on a mounted diatom, for example Pleurosigma or Gyrosigma species?

[Chainsaw_DNA]

Does anyone know what is that round blob that the 2 Coleps are trying to consume (bright field footage)?.

Thanks

I think it's probably an encysted ciliate/protozoan - unless someone else knows different?

Louise

Based on your tip, I've been reading about microbial cysts and that is the best classification that I've seen so far. Thanks, Louise!

[Rossf]

This is a cool concept-definitely deserves experimentation-this is probably a stupid idea but I’ve always wondered with this technique about painting the entire slide with white nail polish or whatever including the sides except the side being illuminated and just leave enough unpainted space in the middle for a coverslip so any side illumination is bouncing back from all painted surfaces-is this a silly idea? I never know with my brain style!
Regards

[Chainsaw_DNA]

This is a cool concept-definitely deserves experimentation-this is probably a stupid idea but I’ve always wondered with this technique about painting the entire slide with white nail polish or whatever including the sides except the side being illuminated and just leave enough unpainted space in the middle for a coverslip so any side illumination is bouncing back from all painted surfaces-is this a silly idea? I never know with my brain style!
Regards

Not a stupid idea at all!
Here is a picture of what I use, which clearly improves the image quality. This white, 3D printed shroud bounces the escaping light, back into the slide edges. This is essentially what you mentioned, but using plastic instead of nail polish.

The opening at the middle-bottom is where the single, high power LED shines the light into the slide's edge.
This technique allows me to see "darkfield" using the SW380T with it's original 40x objective and an aftermarket 60x objective.

Here is another picture, showing the original version of the first picture and a version with a cutout where the coverslip goes, which gives darker backgrounds.

[Rossf]

Yay! Not as dumb as I thought I was! Cheers Chainsaw_DNA! I even thought about the bottom gap of paint where the coverslip goes but didn’t mention it-have you tried covering the top of the slide with plastic as well?-might be overkill but I’m all for throwing in every idea when I’m in an experimental mood..-by the way I really like that murky 3-D look a lot! Maybe cos I use mainly inverted so pretty used to not as sharp but more 3-D looking images with low N/A’s most inverted objectives have-I have a 25x with N/A .22(!) and it images fungal hyphae beautifully-but is pretty useless at anything else..but still a keeper.
Regards ross

[Rossf]

I just realised I missed the most obvious advantage of this technique-having DF with a 40x and 60x without needing an iris is pretty damn cool!
That it. I’m just gonna have to experiment with this technique.
R

[Hobbyst46]

I just realised I missed the most obvious advantage of this technique-having DF with a 40x and 60x without needing an iris is pretty damn cool!

This indeed was some of the motivation of the researcher (Kawano) who several years ago published his version of the whole slide illuminator.

BTW, the white pain or plastic wrap shown above do not contribute significant total reflection within the slide, in my opinion. They can prevent stray light, that is light that hits the specimen on the slide from above or from below, for example when the illuminator beam is thicker then the slide or hits the slide not exactly horizontally. I think black paint might be somewhat better. But anyway, the external coating does not return escaping light back into the slide. There are coatings that would do that (certain teflons).

[Chainsaw_DNA]

Being able to use higher magnification was my primary motivation.
While the SW380T works well with the 4X and 10X objectives, I have not had any luck making darkfield with the 40X objective, and above.

Be aware that the success of edge illumination is highly dependent on the specimen. I've had some success with amoebas and diatoms, but nothing great. Coleps are the best specimen that I've seen so far.
With edge illumination, I get videos that would be impossible otherwise, unless someone can show me how to properly setup my microscope for darkfield using 400X total magnification, and above.


[youtube]https://youtu.be/Xw5ztJMZP1o[/youtube]

I've seen improvement using the white plastic shroud, using a dry slide with diatoms. I'll need to experiment with specimens in water and post a comparison video.

[Chainsaw_DNA]

Liked your videos.

Have you tried this with something else beside pond critters? I'm wondering if the drop of water and coverslip act (along with the slide) as somewhat of a light pipe? If it also works with things like smears and dry mount slides, that could be doubly cool.

Thanks, PeteM. I only tried with slides that had dried out and left behind Diatoms and substrate. In those cases, there was some success. But that was the limit of my experience with dry slides.

[Chainsaw_DNA]

Interesting! I'll have to try that!
I made some similar power LED setups for my my 380T but to use with the darkfield condenser:

10W and 3W LEDs.jpg

Top one is a 10W LED on an aluminium bar, bottom a 3W just on a heatsink. Plus a variable psu though the LEDs are controlled by the constant current buck converters.

Louise

Hi Louise. Which darkfield condenser did you use, and did you get acceptable results?
I've been trying to get DF to work with the stock SW380T condenser but I've only had good results at lower magnifications. I have not been able to get DF with 40X and 60X objectives.

[LouiseScot]

Interesting! I'll have to try that!
I made some similar power LED setups for my my 380T but to use with the darkfield condenser:

10W and 3W LEDs.jpg

Top one is a 10W LED on an aluminium bar, bottom a 3W just on a heatsink. Plus a variable psu though the LEDs are controlled by the constant current buck converters.

Louise

Hi Louise. Which darkfield condenser did you use, and did you get acceptable results?
I've been trying to get DF to work with the stock SW380T condenser but I've only had good results at lower magnifications. I have not been able to get DF with 40X and 60X objectives.

Hi

I modified the Swift to take an Amscope dry darkfield condenser - I 3D printed a simple condenser holder and just used the existing screw holes on the stage. I posted about it on the forum

Louise