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For the point illumination it is just much easier to adjust the angle, i think the Till Photonics system can rotate the point very fast to give the same effect as the ring. An advantage of a ring would be that one does not destroy the coating on the objective when using high laser power.

Olympus had a three laser TIRF illuminator for several years, at least in Europe. This allows to adjust the angle, position and focus for each wavelength independetly and it works very well for simultaenous multi-color TIRF with an image splitter (I have no commercial interest). They now have a four color version which is motorized and also marketed in the US.

The Olympus 150x TIRF objective which we use for single molecule work is an Apochromat but not a PLAN Apo and there is some measurable difference is focus over the field of view. In the center i measured an axial chromatic aberration of only 190 nm for emision at  520 nm and 650 nm . 
  
best wishes

Andreas

-----Original Message-----
From: Cammer, Michael <[log in to unmask]>
To: [log in to unmask]
Sent: Sun, 16 Jan 2011 18:02
Subject: Re: Objective lens chromatic aberration


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I originally posted the message below to the microscopy listserv but reviewing 
he discussion here on chromatic aberration, I thought it would be apropos here 
oo even though it is not really regarding confocal.
A few years ago we were having problems with the first commercial Olympus TIRF 
ystem because we could not get consistent evanescent waves with the one angle 
djustment with the laser lines we had from 405 to 568 nm that were delivered 
ia a single fiber (it was worse when we later added a 633 nm laser).  I 
uggested we pump each laser in through a separate path that could be angled 
ndependently.  We didn't build it, but I think Olympus now sells a TIRF system 
hat does this.
Another issue is that when I first heard about TIRF maybe 15 years ago, it was 
ntroduced as a ring illumination at the outer edge of the back aperture, not as 
 single point or crescent at the periphery on only one side.  A ring, or at 
east a series of points around the periphery, seems like a better way to 
rovide a uniform field due to aberrations from coherent light in the imperfect 
ptics.  Any thought on this?
Sincerely,
Michael
-----------------------ORIGINAL MESSAGE-------------------------------
e have the Nikon TIRF system and have three laser lines
oing into the TIRF arm via a single fiber.  When we project through
he 100X objective through the sample onto the wall we see that the
ines go through the sample at different angles.  (You can see a
icture of the projection at approx 45 degrees at
ttp://www.flickr.com/photos/mcammer/5359189090/ .)  It is also
oticeable in the TIRF images that the field depth is different for
ach wavelength.  Is this unavoidable due to the different
avelengths or is it possible to align the optics better so these
pots would be more coincident?

_________________________________________
ichael Cammer, Assistant Research Scientist
kirball Institute of Biomolecular Medicine
ab: (212) 263-3208  Cell: (914) 309-3270

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