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Adrian is right, there was a change in manufacturing for the Olympus 
20x, I believe in 2009. Before, there was the XLUMPLFL20x NA 0.95 and 
the specially coated IR Version IR-XLUMPLFL20x, which is still used by 
us and others for multi-photon microscopy (although originally designed 
for IR-DIC).

Instead of those then discontinued lenses, the XLUMPLFLN20x (note the N) 
was then offered. I once got the following transmission numbers from an 
Olympus representative, didn't verify them by measuring myself:
                       500 nm   650nm  800nm      1200 nm
XLUMPLFL20x           0.73     0.66    0.60       0.50
XLUMPLFL20x-IR        0.42     0.61    0.74       0.69
XLUMPLFLN20x          0.77     0.77    0.68       0.52

So, for a two-photon process with backward-detected 500 nm emission, if 
you do the math the new one should be better than both old versions, 
essentially because you loose less of the emitted photons: (exc^2 * em.)
                  800/500        1200/500         1200/650
XLUMPLFL20x-IR    0.23            0,2              0.29
XLUMPLFLN20x      0.35            0,21             0.21

This predicted outcome for 500 nm emission was used by Olympus to argue 
that an IR-coated version of the new lens is not needed.

However, if you are interessted in three-photon processes and/or forward 
detection (eg. THG), then you should keep a close eye on any still 
available old IR 20x. Same if you go for two-photon fluorescence with 
red dyes. As far as I know, there is no IR-coated version of the new 
objective (yet), hopefully I am wrong. Maybe if we push this a little.


While we are on the objectives: Did any one of you bothered to measure 
the chromatic aberration for Ti:Sa lasers and OPOs? For our system 
(LaVision BioTech) with the XLUMPLFL20x-IR, I measured a z-shift of the 
focal plane of about 9 µm between 725 and 1050 and about 7 µm between 
1175 and 1300 nm. I am wondering if this is in the normal range.

Steffen


On 20.10.2010 01:11, Adrian Smith wrote:
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> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
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>
> Hi,
>
> If you are referring to the LaVision BioTec systems at Nijmegen then the other reason they will have the 20x is that Olympus won't sell them the 25x as it is not an Olympus system :)
>
> We are in the same boat here with our LaVision BioTec systems with OPO.
>
> We actually have two versions of the 20x Olympus objective - one "normal" and one "special IR"

which has much better transmission in the longer wavelengths. I don't 
have any rigorous numbers

or 25x to compare with so I won't post anything here.
>
> We have also heard that the current 20x Olympus objectives (might be NA 1.0?) are not as good

for the OPO as the older NA0.95 special IR version... so it certainly 
seems that not all Olympus

20x objectives are created equal!
>
> Regards,
>
> Adrian Smith
> Centenary Institute, Sydney, Australia
>
>
------------------------------------------------------------
Steffen Dietzel, PD Dr. rer. nat
Ludwig-Maximilians-Universität München
Walter-Brendel-Zentrum für experimentelle Medizin (WBex)
Head of light microscopy