Dear Nick -

Objectives vary even within the same brand/type. I think that most people who wish to get a perfect objective test them before buying.

Mike

________________________________________
From: Confocal Microscopy List [[log in to unmask]] On Behalf Of Nick Durr [[log in to unmask]]
Sent: Thursday, June 10, 2010 9:17 PM
To: [log in to unmask]
Subject: water immersion objectives for deep nonlinear imaging

Dear List,
We've been using the older olympus XLUMPFL 20x 0.95 NA objective, and have
been getting decent images at large imaging depths. But for two reasons we're
looking into purchasing a new objective. First, when we do point spread
functions measurements for two-photon fluorescence at 780nm excitation with
this lens, we always get measurements that are significantly larger than the
size predicted from the diffraction limit (~30% bigger laterally and ~50% bigger
axially). We're careful about index matching, overfilling the back aperture, etc.,
and can get close to diffraction limited PSFs with other lenses, so I believe this
is a limitation of the lens, probably at NIR wavelengths. Second, we'd like to
get a lens that can be used with a coverslip (preferably one with a correction
collar).

It seems there are at least two objective lenses I can find that would be good
for our upgrade (we also want to have a working distance ~> 1mm): the
olympus 25x 1.05 NA W, and the nikon CFI Apo LWD 25x 1.1 NA W.

Their specs are very similar, so I'm wondering if anyone has had any experience
characterizing them, or can suggest other options that I haven't found. They
both say they are "corrected" out to 950-1000nm, but based on our experience
with the older olympus, I'm doubtful they perform at the diffraction limit in this
range. The Leica HCX 20x 1.0 also seems nice, but doesn't have a correction
collar. Has anyone done PSF measurements on any of these objectives? Or
compared them in any way?
Best Wishes,
-Nick