David Knecht wrote:

> Dear users- What is the effect of not filling the back focal aperture
> of an objective in a point scanning confocal system.  I am assuming
> the same laser power going in, but the beam not expanded as far.  It
> seems to me that it is a different issue than in a normal imaging
> system. Would you get a smaller spot of illumination?

On the contrary, axial spot size will increase considerably. You achieve
optimal resolution when grossly overfilling your back aperture
(otherwise you don't take advantage of the full NA of your objective).
This is generally true in all types of microscopy.

  Christian

--
Christian Soeller                [log in to unmask]
Dept. of Physiology              U. Auckland School of Medicine
Auckland                         New Zealand