Dark Field Lenses

[Peter-J]

Are they all the same diameter. Is the space under the condenser a universal size.

[zzffnn]

They are not.

If you are experienced DIY microscopy (and can align and make mask sizes very precisely), you may be able to get DIY darkfield at NA 0.85; but most people's DIY stops at NA 0.65 (40x dry lens).

[Phill Brown]

Could be worth asking Brunel if there is a filter holder for the SP40.
There is a polariser listed which may fit to the condenser.
If that is the case with some luck it might be possible to modify to hold filters.
As the SP40 is already a done deal it may be some creativity will be needed.
Good luck, some small file size pics will help.

[Dubious]

SP40 seems to have a filter holder, see below, so first step would be to see if a stop placed there works. There are people on Ebay selling darkfield/oblique stop sets for various diameter holders. Sometimes the filter holder is too far below the diaphragm to work well for darkfield, in which case you would need to find a way to insert a darkfield stop higher up. I believe I noticed someone on Ebay selling a retro kit to do that for certain condensers; but you can DIY. Probably worthwhile calling the folks at Brunel to see if they can tell you anything useful, but they may also try to convince you to buy a dedicated darkfield condenser that costs almost as much as the microscope




"SP40 - Binocular

Binocular head with interocular and dioptric adjustment. DIN standard achromatic objectives x4, x10, x40 x100(oil). x10 eyepieces. Mechanical stage with double vernier scales. Coaxial coarse and fine focus controls. Focus safety stop. Focusing substage condenser with iris diaphragm and filter carrier. In built rheostat controlled illumination with field lens. A modern style instrument with a very good specification for the price. Available with LED illumination. Magnification range x40 - x1000."

http://www.brunelmicroscopes.co.uk/mono ... copes.html

[Dubious]

SP40 seems to come with a condenser that has a filter holder, see below, so first step would be to see if a stop placed there works. There are people on Ebay selling darkfield/oblique stop sets for various diameter holders. Sometimes the filter holder is too far below the diaphragm to work well for darkfield, in which case you would need to find a way to insert a darkfield stop higher up. I believe I noticed someone on Ebay selling a retro kit to do that for certain condensers; but you can DIY. Probably worthwhile calling the folks at Brunel to see if they can tell you anything useful, but they may also try to convince you to buy a dedicated darkfield condenser that costs almost as much as the microscope




"SP40 - Binocular

Binocular head with interocular and dioptric adjustment. DIN standard achromatic objectives x4, x10, x40 x100(oil). x10 eyepieces. Mechanical stage with double vernier scales. Coaxial coarse and fine focus controls. Focus safety stop. Focusing substage condenser with iris diaphragm and filter carrier. In built rheostat controlled illumination with field lens. A modern style instrument with a very good specification for the price. Available with LED illumination. Magnification range x40 - x1000."

http://www.brunelmicroscopes.co.uk/mono ... copes.html

[Chas]

Just to be clear.... are asking about dark-field patch stops that fit in the condenser's filter holder, like these:

DF patch stops 640480.jpg (27.68 KiB) Viewed 2716 times

Or about replacing your condenser with dedicated a dark-field one?

[Peter-J]

Yes. Exactly.

[Chas]

I find it easier to measure the diameter of the recess in the filter holder (where the patch stops sit) with a pair of calipers, rather than use a ruler.

[EYE C U]

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