As we have many Members who are proven very skilled in fabrication and LED technology I am hoping that they might find some interest in this method and comment on how it could be delivered by less skilled members !!
From https://groups.yahoo.com/neo/groups/Mic ... ages/89381
Yahoo Group - "Microscopy as a hobby..................."
"Condenser-free contrast methods: Just a simple ring of LEDs illuminating a standard transmitted light microscope is needed for providing condenser-free phase contrast and darkfield microscopy, as well as combinatorial contrast including Rheinberg illumination and simultaneous, colour-contrasted, brightfield, darkfield and Zernike phase contrast."
"Scientific article free full download available at:
http://onlinelibrary.wiley.com/doi/10.1 ... 12181/epdf"
Regards and many thanks
John
Condenser-free contrast methods: Just a simple ring of LEDs
Moderators: rjlittlefield, ChrisR, Chris S., Pau
They sell the LED system commercially for inverted phase scopes:
https://www.cairn-research.co.uk/produc ... luminator/
Optical principle does not seem complex. If one can do accurate ray tracing and optical alignment, it can be done. I wonder how difficult it is for a hobbyist though, to make such a working LED system. Say for high NA darkfield or COL.
That paper was written by a PhD optician in his professional research lab.
Using conventional condenser may end up being cheaper and easier, for us hobbyists? I don't mind trying such a LED system though, if someone makes one for me
https://www.cairn-research.co.uk/produc ... luminator/
Optical principle does not seem complex. If one can do accurate ray tracing and optical alignment, it can be done. I wonder how difficult it is for a hobbyist though, to make such a working LED system. Say for high NA darkfield or COL.
That paper was written by a PhD optician in his professional research lab.
Using conventional condenser may end up being cheaper and easier, for us hobbyists? I don't mind trying such a LED system though, if someone makes one for me
Selling my Canon FD 200mm F/2.8 lens
A fellow came to the Quekett Microscopical Society to demonstrate such a thing. I daresay there's a record on the Club site. From memory he was from a university in middle England.
His first and some current working models used very cheap "angel eyes" led rings, as used on cars and bought for a few pounds on ebay. Darkfield seemed to be easy.
It's something I wondered if clever people like Fotoopa might incorporate into their lighting rigs. I have suggested it occasionally.
I believe Leitz made a phase ring wich could be retro-fitted to some of their objectives, which is intriguing.
I understand the back focal plane of most objectives is inside the metal body, but I have at least one where it's not.
So, how would one make a phase ring?!
Edit - found it: It is the same item.
http://www.quekett.org/about/reports/20 ... ion-public
Go down to the paragraph starting Kevin Webb.
The photo shows an ebay ring setup. The angle is adjusted as you would expect - by altering the height. A Bertrand lens...
His first and some current working models used very cheap "angel eyes" led rings, as used on cars and bought for a few pounds on ebay. Darkfield seemed to be easy.
It's something I wondered if clever people like Fotoopa might incorporate into their lighting rigs. I have suggested it occasionally.
I believe Leitz made a phase ring wich could be retro-fitted to some of their objectives, which is intriguing.
I understand the back focal plane of most objectives is inside the metal body, but I have at least one where it's not.
So, how would one make a phase ring?!
Edit - found it: It is the same item.
http://www.quekett.org/about/reports/20 ... ion-public
Go down to the paragraph starting Kevin Webb.
The photo shows an ebay ring setup. The angle is adjusted as you would expect - by altering the height. A Bertrand lens...
Chris R
Chris R,
You can look at the back focal plane image of an objective by looking down empty eye tube of microscope without eyepieces. That was how that paper's author (Kevin Webb) imaged the published bfp, I believe.
I certainly would like to try such a darkfield LED system, if someone builds one, and compare it with my cardioid darkfield 1.2/1.4 condenser. I have no use for inverted phase LED though.
And such system or idea probably already has patent protection, so commercial production from another company (other than Cairn) is likely not possible/profitable.
And yes, I have heard of fiber optic-coupled side lighting for darkfield too. The problem is finding an affordable option. Those inventions usually cost >$300 and target research/industry users.
You can look at the back focal plane image of an objective by looking down empty eye tube of microscope without eyepieces. That was how that paper's author (Kevin Webb) imaged the published bfp, I believe.
I certainly would like to try such a darkfield LED system, if someone builds one, and compare it with my cardioid darkfield 1.2/1.4 condenser. I have no use for inverted phase LED though.
And such system or idea probably already has patent protection, so commercial production from another company (other than Cairn) is likely not possible/profitable.
And yes, I have heard of fiber optic-coupled side lighting for darkfield too. The problem is finding an affordable option. Those inventions usually cost >$300 and target research/industry users.
Selling my Canon FD 200mm F/2.8 lens
Sure you don't need a Bertrand lens. He used one, as described.
The "$10" setup in the picture does use an inverted scope, but it doesn't have to be. He started off with a normal configuration. Obviously there's more space as shown. The angle of (bend of) the leds, perhaps counter-intuitively, is not hugely critical.
His darkfield worked well to 40x NA 0.65 but at NA>1 the slide/coverslip optically interferes.
I don't know that there would be sufficient interest today in pushing that direction, but the degree of control on the way, could be useful. You could ask him - he's more of an academic than entrepreneur so if there are systems out there, he'd probably let you know.
The "$10" setup in the picture does use an inverted scope, but it doesn't have to be. He started off with a normal configuration. Obviously there's more space as shown. The angle of (bend of) the leds, perhaps counter-intuitively, is not hugely critical.
His darkfield worked well to 40x NA 0.65 but at NA>1 the slide/coverslip optically interferes.
I don't know that there would be sufficient interest today in pushing that direction, but the degree of control on the way, could be useful. You could ask him - he's more of an academic than entrepreneur so if there are systems out there, he'd probably let you know.
Chris R