Re: oil immersion

Andrew, thanks for your answer. I looked it up in a Zeiss magazine, it says:
'To exceed an NA of 1.0, the condenser must be oiled to the back of the
slide.'

I have some more questions about condensers so I'll start a new thread (to
keep this one 'clean').

Regards,

Theo





"Andy Resnick" <andy.resnick@xxxxxxxxxxx> schreef in bericht
news:d9uaes$dsp$1@xxxxxxxxxxxxxxxxxxxxxx
> Theo Griep wrote:
>
>> Is it true that NA > 1.0 can only be achieved with oil between the
>> condensor
>> and object, too?
>
> No. I think what you are really asking is in regards to the relationship
> between the condenser NA and objective NA in terms of maximizing the
> performance of the microscope. I think that the true maximum of
> resolution is obtained when the condenser NA is slightly larger than the
> NA of the objective. Thus, using an oil condenser is recommended when
> performing high NA microscopy.
>
> In practice, this may not be possible (for example, using an inverted
> microscope- our Axiovert 200 has a maximum condenser NA of 0.5). The good
> news is that I have not really noticed a meaningful degredation of the
> image when the condenser is set to 0.5 and using an objective NA of 1.4 as
> opposed to using an oil condenser (NA 1.3) with a NA 1.3 objective on an
> upright. I do notice a big difference when the condenser is stopped down
> to 0.05- a useful trick for finding low-contrast objects- the contrast
> goes way up, but the resolution goes way down.
>
> And when doing epi-illumination the objective is the condenser as well,
> but it's also true that the illumination NA may be smaller than the
> collection NA if the illumination optics are not properly aligned. And,
> in any case, the number printed on the lens may not be the exact NA of the
> actual lens (that is, even though I have a 100X NA 1.3 lens, the lens
> probably doesn't have an NA of 1.300000000000000...)
>
> Furthermore, it's possible to change the NA by changing the immersion
> medium- one trick with using infrared laser tweezers is to increase the
> refractive index of the oil to compensate for the increased spherical
> aberration of the IR light.
>
> Hope this helps...
> --
> Andrew Resnick, Ph.D.
> Department of Physiology and Biophysics
> Case Western Reserve University


.

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