http://confocal-microscopy-list.275.s1.nabble.com/Condenser-lens-choice-for-a-given-objective-tp7584901p7584909.html
(1.22 lambda/(NA_obj +NA_cond)) . The makes sense because even a very
NA of the condenser is large. (This is how dark-field works).
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>
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> *****
>
> Thanks for the feedback, Barbara. It is very helpful.
>
> I have heard the advice before about the condenser NA needing to be
> greater than or equal to the objective NA. Can you offer some physical
> explanation or intuition for why this is?
>
> One admittedly incomplete explanation I can think of for the
> recommendation goes like this: the light collected by the objective
> consists of two parts. One part is the transmitted light that is not
> scattered by the sample. The other part is the light scattered by the
> sample. If the condenser's working NA is smaller than the objective's,
> then the unscattered, transmitted light fills only a portion of the
> objective's back focal plane. However, the light scattered by the
> sample will probably be dispersed across the entire back focal plane
> because it will encode all the spatial frequencies of the sample.
>
> I wonder if it's the inhomogeneous distribution of light from the two
> components in the objective's back focal plane that leads to the
> matched NA requirements of the condenser and objective. Does this make
> sense?
>
> Thanks!
> Kyle
>
> On 03/17/2016 08:22 PM, Barbara Foster wrote:
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>>
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>> posting.
>> *****
>>
>> Hi, Kyle
>>
>> The general rule of thumb is that the NA on the condenser should meet
>> or exceed that of the objective.
>>
>> If you are using oil immersion objectives, ideally, to achieve that
>> goal, you should use an oil immersion condenser, otherwise you are
>> limited to an NA of 0.9.
>>
>> Also, remember that the aperture iris in the condenser adjusts the
>> condenser's WORKING numerical aperture. Just because the condenser
>> is marked 1.4 NA doesn't mean that, in a practical experiment, it
>> will be operating at 1.4. I follow the guidelines set down by Frits
>> Zernicke (inventor of Phase contrast): gently close the aperture
>> iris to the "Oomph" position: that delicate balance between
>> sufficient edge definition and optimum resolution (Yes, the condenser
>> does contribute to resolution).
>>
>> As for planning for growth:
>> You might want to invest in a turret condenser early on. That will
>> give you the option to add those other contrast techniques as you
>> grow into them.
>>
>> And just one more reminder, specifically regarding DIC:
>> If you are going to use plastic vessels (petri dishes, multi-well
>> plates, growth flasks), use Hoffman Modulation Contrast instead of
>> DIC. DIC uses polarized light. The plastic will affectt the shear
>> and cause effects that will be hard to interpret. Some HMC set-ups
>> do use pol to control the width of the slit in the condenser, but all
>> of that is on the incoming side of the sample and will not be
>> affected by plastic containers.
>>
>> Good hunting!
>> Barbara Foster, President & Chief Consultant
>> Microscopy/Microscopy Education ... "Education, not Training"
>> 7101 Royal Glen Trail, Suite A - McKinney, TX 75070 - P: 972-924-5310
>> www.MicroscopyEducation.com
>>
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>> Imaging Place, Inc.
>>
>>
>> NEW! Getting involved in Raman or FTIR?
>> MME is now offering courses in these areas specifically for
>> microscopists!
>> Now scheduling courses through the mid 2016. We can customize a
>> course on nearly any topic, from fluorescence to confocal to image
>> analysis to SEM/TEM.
>> Call today for a free training evaluation.
>>
>>
>>
>>
>> At 08:36 AM 3/17/2016, Kyle Michael Douglass wrote:
>>> *****
>>> To join, leave or search the confocal microscopy listserv, go to:
>>>
http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy>>> Post images on
http://www.imgur.com and include the link in your
>>> posting.
>>> *****
>>>
>>> Hello listers,
>>>
>>>
>>> I have a couple of questions about condensers for you. I'd like to
>>> do some transmitted light imaging in an inverted microscope using
>>> high magnification, oil-immersion objectives. For the moment, I
>>> don't need to do anything other than brightfield with a high power
>>> LED light source. It might be nice to do phase contrast or DIC in
>>> the future, but I don't need it now.
>>>
>>>
>>> My questions are:
>>>
>>>
>>> 1) What are the rules of thumb for matching a brightfield condenser
>>> to an objective? I won't be using anything but oil immersion
>>> objectives with NA's greater than 1.4.
>>>
>>>
>>> 2) If I do want to do phase contrast or DIC in the future, should I
>>> put special consideration into the condenser lens selection now? I
>>> imagine the condenser NA will determine what phase contrast rings I
>>> can use, but does it impact DIC?
>>>
>>>
>>> Thanks!
>>>
>>> Kyle
>>>
>>>
>>> Dr. Kyle M. Douglass
>>> Post-doctoral Researcher
>>> EPFL - The Laboratory of Experimental Biophysics
>>>
http://leb.epfl.ch/>>>
http://kmdouglass.github.io>