Phone illumination - poor man confocal

Here you can discuss different microscopic techniques and illumination methods, such as Brightfield, Darkfield, Phase Contrast, DIC, Oblique illumination, etc.
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patta
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Phone illumination - poor man confocal

#1 Post by patta » Mon Jun 14, 2021 4:53 pm

So I wanted to buy a color filter. But are expensive! Maybe, I'll get a green LED light, it is cheaper. Oh, they sell RGB LED too; that will be cool.
Wait, I have a RGB led array just here: the phone screen. So I started using the phone screen as illumination; just put it under the condenser!

A bit feeble as light source, but usable, and opened up a Pandora box. Can do a lot of things! Under the condenser, Red, Green or Blue illumination. Can design and display Rheinberg illumination patterns, and phase annulus. Can do Rheinberg (x) phase... van Egmond oblique masks... Fourier pthychoghraphy...

It works well also without condenser; under the stage, just removed the condenser. The phase contrast and Rheinberg seem to work better without condenser: no condenser aberrations! Up to very high NA, 0.95 (bit darker though at the extremes). I tried to go higher than NA 1, and oiled a thick glass flat to the screen (yes, phone oiled) but didn't work, there is some gap that does not allow light to escape at higher angle. The phone survived and has been de-oiled.
Sizing and centering the phase annulus... I've set up the phone as second screen for the computer. The annulus can be centered by moving its image with the mouse!
My phone has OLED screen, which gives nice narrow band colors. LCD screen should work just as well - and it emits polarized light!

Then things got worse.
Would be possible to focus the phone screen image on the slide? So can see both the specimen and the phone screen?
Yes, can be done; then, fantasy is the limit to play with structured illumination in a huge range of imaginable ways. Zeiss Apotome cutting, parallel confocal scanning. More or less... Can browse the forum from the eyepiece!

I've done only brightfield confocal - which isn't ideal. With an imaging lens, or another microscope objective, instead of the condenser, projecting the screen image on the specimen. In a reflected light setup, that would be much better, since the image is not defocused and distorted by the specimen (see images in oil immersion). But two attempts at making a beamsplitter failed miserably, so reflected illumination has to wait.
A digital movie projector should do all the same tricks as the phone screen, but with much more light power. Needs to be "plugged in" with some relay lens.

I've found afterwards many similar setups from researchers and some amateur. Called "digital Light processing structured illumination" or so on. Often it is used a DMD (Digital Micro Mirror) as "screen". Using a digital movie projector is essentially the same setup (many projectors have a DMD inside). Why nobody used a projector? Using the phone is really the crudest way (and least bright), maybe I'm the first to do it! But easy to set up, and larger pixel count than the others I've seen (can do 1440x2560 confocal scanning - at least in principle, the objective etc should agree too.)

Also LED arrays, condenserless, are being tried, but usually with few (10x10), powerful LEDs. And with laborious Arduino drivers and breadboards. With the phone, no soldering, the USB chord is enough. Zero lines of code (but some will be needed for automated confocal scanning).

I attach here below the small-size illustrations. I may publish things in more detail later. My imaging and slide preparation skills are what they are... but slowly improving! Are small diatoms that spontaneously generate in the terrace underpots. Single shot photos straight out of the scope, some contrast and brightness adjustment.

This project was from three months ago, I've forgot to post it. Now got on posting streak with the Polychromatic polarization, and this old work came back to memory.

Hope the forum host don't get offended to be used for illumination of diatoms...
Last one is an image to display on the phone, full screen, to get phase annulus etc, if you get the itch and want to try immediately.

Have fun!
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Giorgio
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Setups for phone illumination
Setups for phone illumination
OLED_illumination_microscope_setups_photos_Pattarini2021.jpg (182.82 KiB) Viewed 4318 times
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Comparison Diatoms with Phase and Rheinberg phone screen illumination
Comparison Diatoms with Phase and Rheinberg phone screen illumination
OLED_illumination_microscope_40x_Phase_Pattarini2021.jpg (164.75 KiB) Viewed 4318 times
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Diatoms transmitted confocal 60x1.40 Oil Phone screen illumination
Diatoms transmitted confocal 60x1.40 Oil Phone screen illumination
Photos_confocal_oil.jpg (184.35 KiB) Viewed 4318 times
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Microbehunter host explaining darkfield filters in company of diatoms 10x 0.25 I think
Microbehunter host explaining darkfield filters in company of diatoms 10x 0.25 I think
OLED_illumination_tests_April_2021_Pattarini0010.jpg (96.83 KiB) Viewed 4317 times
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Attachments
Image to display on the screen for phase, Rheinberg, and Bahtinov fine focus
Image to display on the screen for phase, Rheinberg, and Bahtinov fine focus
Phone_illumination_3.png (29.05 KiB) Viewed 4318 times
Last edited by patta on Fri Jun 18, 2021 2:14 pm, edited 15 times in total.

MicroBob
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Re: Phone illumination - poor man confocal

#2 Post by MicroBob » Mon Jun 14, 2021 5:30 pm

patta wrote:
Mon Jun 14, 2021 4:53 pm
(yes, phone oiled)
:lol:

Great idea! And there are lots of older phones one the market for next to no money.

Bob

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patta
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Re: Phone illumination - poor man confocal

#3 Post by patta » Mon Jun 14, 2021 6:47 pm

Thanks! Yes probably an old phone costs less than a led light...

Below another illustration (already posted somewhere here)
Screen set up as "Metz apertometer" to measure the actual Numerical Aperture of (dry) objectives. Also proof that the bare screen works to NA 0.95...
This setup came out from a discussion in the forum binomania.it last year.
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Phone screen as apertometer
Phone screen as apertometer
Apertometer diagram photos.jpg (101.56 KiB) Viewed 4278 times
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Rossf
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Re: Phone illumination - poor man confocal

#4 Post by Rossf » Mon Jun 14, 2021 11:15 pm

Hey patta love that spirit of adventure and experimentation! As soon as I read an article about condenserless phase contrast/dark field rheinberg using circles of LED’s I’ve had similar thoughts-just being able to make anulus on the fly and all sorts of color combinations.I wonder if one could use one of those really small digital projectors (about the size of cigarette pack) aimed at a mirror? I actually use my iPhones torch light quite a bit on some old scopes I can’t be bothered setting up a proper illuminator-as long as condenser has good quality diffuser works well!
Keep it up!
Regards ross

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patta
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Re: Phone illumination - poor man confocal

#5 Post by patta » Thu Jun 17, 2021 4:35 pm

Rossf wrote:
Mon Jun 14, 2021 11:15 pm
I wonder if one could use one of those really small digital projectors (about the size of cigarette pack) aimed at a mirror?
Good, thanks for the motivation! Phones are such a powerful device in our pockets. They can even make phone calls!
Yes sure a small projector is interesting.
The 30$ ones may be ok to work in the aperture plane, they have resolution like 300x400. Not sure if they actually fit under the stage, they're like 100+ mm tall. Luckily we have vintage microscopes that were fitted with the swinging mirror...
The micro-ones, no, I think they've too small lens and may need some extra relay lens to fit the illumination path. And are expensive. I would rather go for a standard, full-size one then, with some high resolution so can do the confocal tricks, and mount it permanent to the scope.
No time at the moment but I'll get one at some point.

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iconoclastica
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Re: Phone illumination - poor man confocal

#6 Post by iconoclastica » Fri Jun 18, 2021 9:42 pm

It is possible to use the lcd screen without the phone attached, as 'filter' over the microscope's own light source. I do have a very interesting publication on that on my other computer. i will add the link tomorrow. That project has been on my wish-to-do-list for over two years now. I got second thoughts when I couldn't find a suitable monochrome lcd-screen and found it hard to predict what colour screens would do (what with sub-pixels). Perhaps I just should have tried it...

--- edit ---:

Microscopy illumination engineering using a low-cost liquid crystal display

tpruuden
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Re: Phone illumination - poor man confocal

#7 Post by tpruuden » Tue May 24, 2022 3:15 am

The source of light modulation can also be DLP projector. Check this thread about Aurox and other methods:
viewtopic.php?f=5&t=15272

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