In recent news: https://www.nature.com/articles/s41587-023-01740-9
The full 21 page article is linked from that briefing note:
https://www.nature.com/articles/s41587-023-01717-8.pdf
MichaelG.
.
Encouraging Note from pages 6-7
.
Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.
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Schmidt objective
Schmidt objective
Too many 'projects'
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Scarodactyl
- Posts: 2794
- Joined: Sat Mar 03, 2018 9:09 pm
Re: Schmidt objective
This did look very interesting and I am curious how well it will work in practice (especially the part about being less expensive to make, the mentioned ASI/special optics objectives are like 20k and up).
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apochronaut
- Posts: 6327
- Joined: Fri May 15, 2015 12:15 am
Re: Schmidt objective
I like the idea. It theoretically solves some of the problems assiciated with the Cassagrain objectives but it does specify a " collimated " light source. How collimated? Do you need another objective as a condenser, as is the case with the Cassegrains?
Re: Schmidt objective
That is very nice, I like the idea of using the immersed mirror as main magnification element - so it doesn't care about the refractive index of the immersion medium.
Their application is looking inside larvas of fish - pretty thick and irregular specimen, so they want to match the index of the refractive medium with the inner body tissues.
They've used it in Confocal scanning configuration, it doesn't need a condenser, is like coaxial reflected illumination, see the beamsplitter in the setup.
The "highly collimated laser light" is for another unrelated trick to make confocal scanning even more contrasty, deep in the thick specimen (that us amateur cannot afford): two-photon fluorescence, meaning you shoot the illumination laser so crazy powerful that where the illumination is concentrated (at the focal point inside the specimen) the photons are very dense and they work together: two photons of 600nm wavelength "fuse" and work as one UV photon 300nm; this one high energy photon excite fluorescence.
This method is very useful to observe thick specimens, since the photons "fuse" only in the focal point, while everywhere else they're just normal 600nm photons, that do not excite fluorescence. So you get fluorescence only in the focal point that you're observing, where there are those "300nm photons", and no haze or mess from out-of-focus stuff.
- sorry for the weakly related pontification, long time since -
Their application is looking inside larvas of fish - pretty thick and irregular specimen, so they want to match the index of the refractive medium with the inner body tissues.
They've used it in Confocal scanning configuration, it doesn't need a condenser, is like coaxial reflected illumination, see the beamsplitter in the setup.
The "highly collimated laser light" is for another unrelated trick to make confocal scanning even more contrasty, deep in the thick specimen (that us amateur cannot afford): two-photon fluorescence, meaning you shoot the illumination laser so crazy powerful that where the illumination is concentrated (at the focal point inside the specimen) the photons are very dense and they work together: two photons of 600nm wavelength "fuse" and work as one UV photon 300nm; this one high energy photon excite fluorescence.
This method is very useful to observe thick specimens, since the photons "fuse" only in the focal point, while everywhere else they're just normal 600nm photons, that do not excite fluorescence. So you get fluorescence only in the focal point that you're observing, where there are those "300nm photons", and no haze or mess from out-of-focus stuff.
- sorry for the weakly related pontification, long time since -
Last edited by patta on Thu Apr 20, 2023 11:49 am, edited 10 times in total.
Re: Schmidt objective
Oh remembered, I've made a similar setup time ago: observing a small spherical mirror with 4x objective.
No confocal, immersion nor two-photons. Immersion could be done with a chamber, but not easy to put the microscope horizontal (oh wait, the old horseshoe stand tilts)
How to make the spherical mirror:
-take a small rectangle of aluminium or brass plate, or a coin (better if polished, but also rough works)
- take a steel ball from ball bearing, 3 to 8 mm diameter
-clean all and oil the coin (immersion oil, n=1.52 recommended)
-press the ball in the coin, in a a vice or with an hammer blow
- voilà, you have a pretty decent concave mirror
( incidentally, see my profile photo for details of the process
)
The mirror itself alone can work as high magnification objective. (Apochromatic! Lot of spherical aberration though)
Put on the microscope stage is more manageable; only the 4x objective has enough field and working distance to get the focus of the mirror. The mirror works then as "magnification and NA boost".
The difficulty now is how to hang a specimen a few mm over it; all that I've manage to watch was the dust over the front lens of the objectives....
No confocal, immersion nor two-photons. Immersion could be done with a chamber, but not easy to put the microscope horizontal (oh wait, the old horseshoe stand tilts)
How to make the spherical mirror:
-take a small rectangle of aluminium or brass plate, or a coin (better if polished, but also rough works)
- take a steel ball from ball bearing, 3 to 8 mm diameter
-clean all and oil the coin (immersion oil, n=1.52 recommended)
-press the ball in the coin, in a a vice or with an hammer blow
- voilà, you have a pretty decent concave mirror
( incidentally, see my profile photo for details of the process
)The mirror itself alone can work as high magnification objective. (Apochromatic! Lot of spherical aberration though)
Put on the microscope stage is more manageable; only the 4x objective has enough field and working distance to get the focus of the mirror. The mirror works then as "magnification and NA boost".
The difficulty now is how to hang a specimen a few mm over it; all that I've manage to watch was the dust over the front lens of the objectives....