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Direct LED illumination?

 
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GaryB



Joined: 29 Jul 2016
Posts: 373

PostPosted: Sun Jul 16, 2017 5:06 am    Post subject: Direct LED illumination? Reply with quote

Hey all Smile
I've been playing with condenser-less lighting again and it got me wondering why it's not used more often as it seems to work pretty well from my tests. I got the idea from the old Zeiss Lucigen condenser which uses an 9mm opal glass diffuser over a bulb and the NA is set by raising or lowering to fill the objective backplane. It's a simple concept and reports have it that it works as well as a conventional setup.

I replicated the effect by using a Cree CXA 1310 High Density LED Array.
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I mounted it to a block of aluminum and sat it on the condenser rack to move up and down. It fills the objective backplane easily and the brightness and resolution appear to be the same as my usual condenser setup. It has the advantages of simple centering, no condenser induced aberrations and can easily be offset a little for oblique and even more for darkfield. It's very bright, cool and simple in use, so I was wondering why lighting like this isn't more widely used now that we have compact, dense arrays like the CXA. I imagine the CXA 1520 version would be even better as its a coupe of mm's wider and would cover all lens NA's available like the Lucigen can.
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Pau
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Joined: 20 Jan 2010
Posts: 3955
Location: Valencia, Spain

PostPosted: Sun Jul 16, 2017 7:47 am    Post subject: Reply with quote

Nice idea, Gary

If the illuminated surface is really even it will work exactly like the Lucigen likelly with much higher light intensity. Pictures taken of the blank field could help to test it.

Quote:
...and it got me wondering why it's not used more often as it seems to work pretty well from my tests.
The Zeiss Lucigen itself was not a commercial succes, there are lots of good ideas lost in the microscopy history.
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dolmadis



Joined: 07 Dec 2011
Posts: 353
Location: UK

PostPosted: Sun Jul 16, 2017 7:53 am    Post subject: Reply with quote

Hi Gary

To someone who struggles with electronics may I ask please what is the rest of the set up with power source, voltage, led drivers, other components etc.,?

Many thanks


John
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zzffnn



Joined: 22 May 2014
Posts: 1449
Location: Texas USA

PostPosted: Sun Jul 16, 2017 8:04 am    Post subject: Reply with quote

Gary,

Can you go over NA 0.65, without a regular condenser lens? Lower that that, you won't have much problem. I think you still need an iris above LED to cut flare.
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GaryB



Joined: 29 Jul 2016
Posts: 373

PostPosted: Sun Jul 16, 2017 4:32 pm    Post subject: Reply with quote

dolmadis wrote:
Hi Gary

To someone who struggles with electronics may I ask please what is the rest of the set up with power source, voltage, led drivers, other components etc.,?

Many thanks


John


Hi John,
the power supply was an old laptop brick rated at 16v 4A that I bought on ebay years ago. This type would do
http://www.ebay.com/itm/KORG-KA260-SONY-AC-V018-I-T-E-A-C-Power-Supply-Adapter-18V-3-33A-Laptop-Charger-/400709994077?hash=item5d4c2d465d:g:F5gAAOxynwlTc~QO
that's connected to one of these Dimmers
http://www.ebay.com/itm/DC-LED-Switch-Dimmer-Controller-for-3528-5050-12-24V-8A-Single-Color-LED-Strips-/282292464694?epid=1052368959&hash=item41b9f12c36:g:FB8AAOSw-0xYfhME
It's very simple and works very well.... and cheap! Laughing

Fan, yes it does go over .65 when raised close to the slide, it replaces the condenser completely. The thing with the Lucigen style is that to get the 80% fill normally achieved with the iris you just lower the lamp a little. That cuts down glare in the same way an iris does. With the larger 35V version, you could go to 1.4NA if oiled. This would require adding a small glass diffuser onto the array for oiling purposes but there's no reason it can't replicate the Lucigen fully as far as I can see.

Pau, I think the failure to take off is more of a psychological issue, that something so simple and cheap could be any good. I don't know. It does have definite drawbacks though. Filters, masks and so forth are more difficult to apply with this lighting type as they have to go over the light rather than below a condenser, so there is that. Still, fun times playing.
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zzffnn



Joined: 22 May 2014
Posts: 1449
Location: Texas USA

PostPosted: Sun Jul 16, 2017 7:21 pm    Post subject: Reply with quote

Gary,

If you can make a direct LED version of the Leitz Heine, I would be happy to test and compare them. Twisted Evil
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GaryB



Joined: 29 Jul 2016
Posts: 373

PostPosted: Sun Jul 16, 2017 7:30 pm    Post subject: Reply with quote

Hah, I'd love to make a Heine version... sadly I have no idea how. I'm still a little confused about the raypaths of the Heine. I have the drawings and patent files but figuring it out is difficult. I even went as far as modeling it in 3d as accurately as I could and sent it through a rendering program to see if the light paths would go as expected but the results were iffy at best.

Oh to be as smart as Herr Heine was! Very Happy
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ChrisR
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Joined: 14 Mar 2009
Posts: 7177
Location: Near London, UK

PostPosted: Mon Jul 17, 2017 9:54 am    Post subject: Reply with quote

Perhaps when we have addressable leds within the thing, selecting NA, phase (per objective), darkfield and oblique will be by flick of a switch?
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GaryB



Joined: 29 Jul 2016
Posts: 373

PostPosted: Mon Jul 17, 2017 6:16 pm    Post subject: Reply with quote

Wouldn't that be awesome! Very Happy
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GaryB



Joined: 29 Jul 2016
Posts: 373

PostPosted: Tue Jul 18, 2017 3:18 pm    Post subject: Reply with quote

One of the things that got me going on this was an article about condenser free phase contrast here:
http://onlinelibrary.wiley.com/doi/10.1111/jmi.12181/full

It shows that led rings are virtually indistinguishable from phase rings, fully adjustable for any phase objective by moving the led ring up or down. It also works for darkfield but the individual light dots can be seen on the specimens. Anyway, I was thinking that with the right combination of flat array like the Cree with a ring led around it, if switching between them and having good travel distance, you could get bright, oblique, dark, COL, Rheinberg and phase in one unit.

I don't have the facilities to make such a beast but I see no reason for it not to work.

Food for thought....
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ChrisR
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Location: Near London, UK

PostPosted: Tue Jul 18, 2017 4:26 pm    Post subject: Reply with quote

That fellow used "angel eyes" (as for vehicles) at least at first. In other words the light sources were much larger - and of course further away.
Does anyone make concave spherical arrays of LEDs ?? Very Happy
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GaryB



Joined: 29 Jul 2016
Posts: 373

PostPosted: Tue Jul 18, 2017 4:44 pm    Post subject: Reply with quote

Yeah, that's one of the problems I've come across, finding rings small enough for uprights. Adafruit makes some small sized rings which are RGBW using 12 led's and are fully configurable with arduinos and raspberry pi. I can't find a lumen rating though. I do have some angel eyes and they are bright enough, just a bit too big to be really useful (43mm externally) but they do work with some jiggery-pokery.

We need some engineers on the case to make a dedicated microscopy version. Condensers are good but I feel this should be the new frontier in lighting as it's way more versatile for general purpose usage and much simpler to get a wide variety of lighting techniques at comparatively minimal cost.
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