Barlow VS Eyepiece

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qanunji
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Barlow VS Eyepiece

Post by qanunji »

Hi,
I desire more magnification for photography from my SZ6045 stereo microscope.
Theoretically, which will give the best resolution, a barlow lens at the front or a higher magnification projection piece?
thanks

Scarodactyl
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Re: Barlow VS Eyepiece

Post by Scarodactyl »

A 2x barlowe/quxiliary lens increases resolution (and decreases working distance) allpwing mpre details to be made out. In contrast a higher power eyepiece increases magnification without any increase in resolution.

qanunji
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Re: Barlow VS Eyepiece

Post by qanunji »

Thanks, I didnt know it increases resolution, now the choice is clear

zed
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Re: Barlow VS Eyepiece

Post by zed »

Scarodactyl wrote:
Sun Jul 11, 2021 10:14 am
A 2x barlowe/quxiliary lens increases resolution (and decreases working distance) allpwing mpre details to be made out. In contrast a higher power eyepiece increases magnification without any increase in resolution.
A Barlow lens most certainly does not increase the resolution of a microscope. Resolution is a function of the NA of the objective and wavelength of light. Intermediate lenses like a Barlow will effect magnification only.

Now you could argue that changing the magnification projected onto the camera can increase overall image resolution - but this will depend on the pixel size of your camera relative to the NA of the objective. It deserves clarification however that this is not the same as increasing the resolution of the optical system.

Duke
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Re: Barlow VS Eyepiece

Post by Duke »

Zed
Actually you are wrong and Scarodactyl is right.
Not in calling Auxiliary lens 2x for greenough stereo microscope 'Barlow lens', of course, that's not, but right in terms of general subject of the discussion.
Auxiliary lens 2x does shorten the focus distance of the objectives by twice, as subsequently it increases the numerical aperture of the objectives twice as well, that's is obvious from the geometrical law of optics.
That said this lens doesn't however double the effective resolution of the system, no, because of the optical aberrations, however it does offer reasonable resolution improvement for it to exist.
“Thoroughly conscious ignorance is the prelude to every real advance in science.” - JCM

Scarodactyl
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Re: Barlow VS Eyepiece

Post by Scarodactyl »

A high quality 2x will certainly double resolution--look at spec sheets for Leica or Zeiss greenough stereos (quoted in lp/mm rather than NA)--maybr not across the whole FoV but thede sre greenough stereos anyway. Likely a low end one will still do so in the very center of the FoV.
Auxiliary objectives are often sold as barlow (or often 'barlowe' for some reason) lenses by importers, though you won't see name brands use the terminology. I do not think it's technically inaccurate though, thry're just used differently on a stereo than they would be in a telescope.

zed
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Re: Barlow VS Eyepiece

Post by zed »

Apologies everyone - I totally misconstrued the original question. For whatever reason I did not equate the term 'Barlow' lens with a front lens on a stereo. :shock:

Image

Scarodactyl
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Re: Barlow VS Eyepiece

Post by Scarodactyl »

No worries, if you're not cruising amscope listings and the like you might never run into that terminology on a stereo microscope.

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