Natural Science Forum / Physics / Optics / March 2006

When we take away the emission filter and look via the eyepieces we see
2 different spots of our laser light.

Description of our optical path:
We focus our 405nm laser beam through a dichroic mirror which reflects
the beam to the back focal plane of an Olympus PLAPON60XO/TIRFM oil
objective (we want illuminate exit samples with a collimated beam).
These are reflections and not fluorescence spots - using a 406/15
emission filter did not change this phenomenon. We had also similar
observations with some other objectives. It occurs both if we put
immersion oil on the objective and also without it. And of course no
sample is on the objective in that test.

Did anybody come across the same problem using similar wavelength and
using that Objective? Did someone here have other similar observations?
Should we see any spot at all if the system is "fine"?

Lots of thanks,
Adi