MicrobeHunter.com Microscopy Forum

I am curious if there are examples of mass-produced, somewhat-modern (say ~1950s or later) microscope illumination systems with all of these characteristics:

1. Intended to support techniques other than bright field.
2. Nonuniform source such as a coiled filament.
3. Source sharply focused in a conjugate of the objective rear focal plane.
4. No diffusing elements.

I'm only Nikon, so here's a list of Nikon scopes that match your criteria.

1.S-Ke (L-Ke)
2.Apophot
3.Biophot
4.Microphot (SA,FX,FXA)
5.E600,E800,E1000

abednego1995 wrote: ↑

Thu Aug 06, 2020 10:26 pm

5.E600,E800,E1000

I have never used any of these microscopes so I could be misunderstanding, but the E1000 manual actually indicates two different diffusers ("Purpose: Diffuse the light at the light source.") that can be selected in/out of the illumination path. One says "Select it when the motorized micro/macro condenser is used." and the other "Select it when the general condenser is used." So it sounds like there would always be a diffuser present during normal use?

The E600 manual also shows a selectable diffuser, although it apparently requires a tool to change and I didn't see anything saying what the use case or default setting would be.

Hans, if you haven’t read this, it may be of interest to you ... specifically the “hidden assumption” section.

http://www.microscopy-uk.org.uk/mag/ar ... ohler.html

Zuul wrote: ↑

Fri Aug 07, 2020 1:39 am

... specifically the “hidden assumption” section.

Thanks, I had not even considered what effect the filament not being planar might have. I was starting to worry I might run out of non-biological things to do with my microscope and be forced to actually hunt for microbes or something.

Mr Overney’s first reference is available here:
https://archive.org/details/cbarchive_4 ... 3/mode/2up

... with the option to download in various formats

MichaelG.

>Hans

Good point. Though I listed the E series as "diffusorless" actual operation normally is favored with the diffusor in the light path in diascopic illumination. This is due to compromises in the design that doesn't allow for filament position adjustment. The filament image is too large at low NA, too small at high NA. With the diffusor inserted it works "so-so" for all. Probably more of a theoretical problem for Koehler purists. However, when you use the oil DF condenser, the normal setup with the diffusor is lossy and dark, whereas without the diffusor, the illumination train can't fill the maximum aperture. Hence they provide a beam expander as an option.

abednego1995 wrote: ↑

Fri Aug 07, 2020 5:00 am

The filament image is too large at low NA, too small at high NA. With the diffusor inserted it works "so-so" for all. Probably more of a theoretical problem for Koehler purists.

Thanks for the details, I suspect the Reichert 410 is like this but it is hard to tell exactly what is going on because the diffuser is a frosted surface of the collector lens so I am unable to attain the "pure Koehler experience" of viewing the filament through a phase telescope.

abednego1995 wrote: ↑

Thu Aug 06, 2020 10:26 pm

2.Apophot

This example is interesting, from here: "...a zoom lens system adjusts the image of the light source on the conjugate plane at the condenser diaphragm..."

Seems like there is not much information about it on the internet. Have you used one? Does the zoom system allow you to maintain a constant magnification of the filament to the objective rear focal plane for all objectives?

MichaelG. wrote: ↑

Fri Aug 07, 2020 3:44 am

Mr Overney’s first reference is available here:
https://archive.org/details/cbarchive_4 ... 3/mode/2up

After several minutes admiring the one figure, it occurred to me, my username may be misleading. I am just an American who happens to be named Hans, and unfortunately speak no German.

hans wrote: ↑

Fri Aug 07, 2020 7:47 pm

After several minutes admiring the one figure, it occurred to me, my username may be misleading. I am just an American who happens to be named Hans, and unfortunately speak no German.

DeepL might be your saviour:
https://www.deepl.com/en/translator

MichaelG.

Yeah that article is a gas. Scientists had some fun in the 19th century.

>Hans

Yes, nice microscope but I don't own one. Too large and cumbersome with too little fraternity:-)
The Apophot has a dial which has settings for each magnification, so as long as the operator is keen to adjust it every time they change mags it works like a charm. But again it's up to the operator. Another microscope that has the feature is the UnivaR by Reichert (1973). The UnivaR had everything electronically coupled, so of course this was automagically tended to.

abednego1995 wrote: ↑

Sat Aug 08, 2020 9:55 am

Another microscope that has the feature is the UnivaR by Reichert (1973).

Quite an impressive-looking microscope, no shortage of room in the stand for a zoom system, I suppose.

Have you ever seen a manual/brochure showing approximately the layout of the optics in one of these systems? Apophot, UnivaR, or any other?

FWIW, here's a 'sketchy' diagram of the Univar optics, pun intended. The relay system is that horizontal path with the trapezoidal prism that loops up to the left & back.

wporter wrote: ↑

Sat Aug 08, 2020 8:56 pm

FWIW, here's a 'sketchy' diagram of the Univar optics, pun intended.

Thank you, before even speculating about which parts are the illumination zoom, it looks like this diagram is showing four separate illumination sources that can be directed in various combinations into the transmitted/reflected paths?

it looks like this diagram is showing four separate illumination sources that can be directed in various combinations into the transmitted/reflected paths?

With so-called 'mirror housing 4', yes. I have mirror-housing 2, so am limited to choices involving hbo/xbo (on the right side of the scope) and 100w halogen (on the left side).

Below is the sketch showing the relay area and the illumination zoom. The zoom is detailed more in patent 3,876,289, assigned to American Optical in 1975.

wporter wrote: ↑

Sat Aug 08, 2020 11:08 pm

The zoom is detailed more in patent 3,876,289, assigned to American Optical in 1975.

Thanks, I was about to say, with no rays traced out and no indication of which elements move, probably hopeless for me to conclude much beyond, "yup, that's a lot of lenses."

hans wrote: ↑

Thu Aug 06, 2020 4:51 am

No diffusing elements.

An AO model 120 has convenient knobs for switching diffuser in or out,
and for focusing the collector lens (called condenser) on the filament.

Nearly all AO infinity options, including Bertrand to facilitate lamp filament focus, can be employed.
https://blekenbleu.github.io/microscope/AO/