Posted by
Andreas Bruckbauer on
URL: http://confocal-microscopy-list.275.s1.nabble.com/Re-Objective-lens-chromatic-aberration-tp5929621p5933642.html
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I guess the initial question about chromatic aberration and the new one about TIRF got muddeled up. I guess chromatically different NA in TIRF could arise when part of the correction is build in the tube lens? The illumination light forTIRF "through the objective" does not pass the tube lens and is thus is not well corrected. Furthermore slight imperfections in the dichroic which relfects the laser light can lead to distortions and these can be wavelength dependent.
best wishes
Andreas
-----Original Message-----
From: Craig Brideau <
[hidden email]>
To:
[hidden email]
Sent: Mon, 17 Jan 2011 19:01
Subject: Re: Objective lens chromatic aberration
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This would also lead to chromatically dependent NA, which would be a big
no-no for a corrected objective.
Craig
On Sun, Jan 16, 2011 at 2:16 PM, Mark Cannell <
[hidden email]>wrote:
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>
> I suggest it is much more likely that the fiber/rear aperture coupling lens
> was at fault. I must admit I don't see how with rear aperture illumination
> the same and same focal length for the 3 lasers how the incident rays could
> have different angles ...
>
> Cheers
>
>
>
> *****
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>>
>> Hi Michael,
>>
>> There are a few factors that need to be compromised in TIRF. 1) The TIRF
>> penetration depth is dependent upon the wavelength of the incident
>> illumination, the angle of incidence, and the refractive indices of the
>> media at the interface. 2) An apochromatic lens brings lasers of three
>> wavelengths on to the same focal plane, but may not to the same incident
>> angle. Therefore, the incident angles for the three lasers should be able
>> to be adjusted independently to get optimal TIRF images.
>>
>> You may want to take your sample off first, to see how different the
>> angles
>> of the three lasers projecting to the wall, to get an idea of the incident
>> angles of your lasers coming out of the objective.
>>
>> Regards
>>
>> Gary G Li, PhD
>>
>>
>> On Sun, Jan 16, 2011 at 1:02 PM, Cammer, Michael <
>>
[hidden email]
>>
>>> wrote:
>>>
>>
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>>>
>>> I originally posted the message below to the microscopy listserv but
>>> reviewing the discussion here on chromatic aberration, I thought it would
>>> be
>>> apropos here too even though it is not really regarding confocal.
>>>
>>> A few years ago we were having problems with the first commercial Olympus
>>> TIRF system because we could not get consistent evanescent waves with the
>>> one angle adjustment with the laser lines we had from 405 to 568 nm that
>>> were delivered via a single fiber (it was worse when we later added a 633
>>> nm
>>> laser). I suggested we pump each laser in through a separate path that
>>> could be angled independently. We didn't build it, but I think Olympus
>>> now
>>> sells a TIRF system that does this.
>>>
>>> Another issue is that when I first heard about TIRF maybe 15 years ago,
>>> it
>>> was introduced as a ring illumination at the outer edge of the back
>>> aperture, not as a single point or crescent at the periphery on only one
>>> side. A ring, or at least a series of points around the periphery, seems
>>> like a better way to provide a uniform field due to aberrations from
>>> coherent light in the imperfect optics. Any thought on this?
>>>
>>> Sincerely,
>>>
>>> Michael
>>>
>>> -----------------------ORIGINAL MESSAGE-------------------------------
>>> We have the Nikon TIRF system and have three laser lines
>>> going into the TIRF arm via a single fiber. When we project through
>>> the 100X objective through the sample onto the wall we see that the
>>> lines go through the sample at different angles. (You can see a
>>> picture of the projection at approx 45 degrees at
>>>
http://www.flickr.com/photos/mcammer/5359189090/ .) It is also
>>> noticeable in the TIRF images that the field depth is different for
>>> each wavelength. Is this unavoidable due to the different
>>> wavelengths or is it possible to align the optics better so these
>>> spots would be more coincident?
>>>
>>>
>>>
>>> _________________________________________
>>> Michael Cammer, Assistant Research Scientist
>>> Skirball Institute of Biomolecular Medicine
>>> Lab: (212) 263-3208 Cell: (914) 309-3270
>>>
>>>
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