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Gert  van Cappellen wrote:

>When exiting a rhodamine film on a coverslip we measure with a 63x 1.4
>NA lens a half with beam diameter of about 1µm. This was done with a
>Zeiss LSM510.

This is very worrying - do other LSM 510 users get similarly
bad results?  One possibility is extreme underfilling of the
lens pupil since on that lens the pupil will be quite large.
Does the 510 have beam expansion under user control, like
the Leica?  Obviously if you are filling only half the pupil
you have an NA 0.7 lens forming the spot (but even that should
give 0.5µm half-width).  If you can, try checking your beam
expansion (even using an alignment prism or piece of paper to
see the beam size with the lens removed).  Something must be
seriously wrong and this is about the only thing I can think
of!  (Unless your measurement is wrong, of ocurse - how are
you measuring it?)

                                                Guy


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