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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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