Phone illumination - poor man confocal
Posted: 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!
.
Giorgio
. . . . .
.
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!
.
Giorgio
. . . . .
.