Re: Boosting bright field resolution with dichroic filters

Posted by Michael Model on
URL: http://confocal-microscopy-list.275.s1.nabble.com/Boosting-bright-field-resolution-with-dichroic-filters-tp7583983p7584001.html

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It must be a little different here because in bright field the sources are
partially coherent - the smaller the condenser aperture the more coherent.
Fluorescent sources are incoherent and astronomical objects are coherent, I
believe. - Mike

On Tue, Jul 14, 2015 at 8:55 AM, Steffen Dietzel <[hidden email]>
wrote:

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>
> Joachim,
>
> thanks for the link. (Barbara, the mail server broke it in two lines, you
> have to copy both parts, then it worked for me.)
>
> I am far from understanding all the formulas there, but I seem to
> understand that it boils down to a Rayleigh criterion for two point light
> sources (on page 3).
> The circular aperture in this example would be the magnifying lens (with
> diameter d) with a distance s between to point light sources. Then it is
> said that sin(alpha)= 1.22* lambda/d
>
> Not sure how to transform this approach that seems to be developed for
> Astronomy to the resolution in the microscope,  but assuming that works
> (and I don't doubt it), I am still not convinced that this point light
> source approach is the right one for brightfield = absorption microscopy,
> where we do not have light sources in the focal plane. Text books tend to
> suggest fluorescence -> Rayleigh and bright field -> Abbe.
>
> Steffen
>
> Am 13.07.2015 um 17:13 schrieb Hehl Joachim:
>
>> *****
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>>
>> Hi Steffen,
>> Good question! The factor 0.61 comes from the calculation of the intensity
>> distribution of light after the diffraction at circular apertures.
>> Here is a link in german
>>
>> http://www.chemgapedia.de/vsengine/vlu/vsc/de/ph/14/ep/einfuehrung/wellenop
>> tik/interferenz2e.vlu.html
>> Best
>> Jo
>>
>> ETH Zürich
>> Joachim Hehl
>> Staff Scientist
>> ScopeM - Scientific Center for Optical and Electron Microscopy
>> HPM E 14
>> Otto-Stern-Weg 3
>> CH-8093, Zurich
>> Switzerland
>>
>>
>> Web: www.lmc.ethz.ch
>> Phone:     [phone]
>> Natel:     [phone]
>> Fax:       [phone]
>> e-mail: Joachim.Hehl <mailto:[hidden email]>@
>> scopem.ethz.ch
>>
>>
>>
>>
>>
>>
>>
>>
>> On 7/13/15 11:26 AM, "Steffen Dietzel" <[hidden email]> wrote:
>>
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>>> To join, leave or search the confocal microscopy listserv, go to:
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>>> posting.
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>>>
>>> Dear all,
>>>
>>> two questions, first about the formula:
>>>
>>> I thought 0.61*lambda/(NA)  (Rayleigh) would be the appropriate formula
>>> for self-luminous objects (dark field, fluorescence) while for bright
>>> field the fitting variant of the Abbe formula should be applied:
>>> lambda/NA-obj for central illumination, lambda/2NA for NA-obj = NA cond
>>> and, in general, lambda/(NA-obj + NA cond), provided that NA-obj is
>>> equal or bigger than NA-cond.
>>>
>>> It seems though, that others are happy with 1.2*lambda/(NA-obj + NA
>>> cond). Where does the 1.2 (or 2*0.6)  in a bright field situation come
>>> from? Would that be the paper by Hopkins and Barham (1950), that Mike
>>> was referring to? Because I have no hope of understanding this paper by
>>> reading through during this life (Lots of formulas my biologist's brain
>>> is not flexible enough to adjust for).
>>>
>>> Second:
>>> Is there a good source for diatoms that can be stained with fluorescent
>>> dyes and self-mounted, as George suggested? I have a few diatom slides
>>> for teaching (Pleurosigma), but they came already mounted.
>>>
>>> Steffen
>>>
>>>
>>>> --
>>>> ------------------------------------------------------------
>>>> Steffen Dietzel, PD Dr. rer. nat
>>>> Ludwig-Maximilians-Universität München
>>>> Walter-Brendel-Zentrum für experimentelle Medizin (WBex)
>>>> Head of light microscopy
>>>>
>>>> Marchioninistr. 27
>>>> D-81377 München
>>>> Germany
>>>>
>>>
> --
> ------------------------------------------------------------
> Steffen Dietzel, PD Dr. rer. nat
> Ludwig-Maximilians-Universität München
> Walter-Brendel-Zentrum für experimentelle Medizin (WBex)
> Head of light microscopy
>
> Marchioninistr. 27
> D-81377 München
>
> Phone: [phone]
> Fax-to-email: +49/89/2180-9976509
> skype: steffendietzel
> e-mail: [hidden email]
>
>
> --
> ------------------------------------------------------------
> Steffen Dietzel, PD Dr. rer. nat
> Ludwig-Maximilians-Universität München
> Walter-Brendel-Zentrum für experimentelle Medizin (WBex)
> Head of light microscopy
>
> Marchioninistr. 27
> D-81377 München
> Germany
>