Mike
There are companies that make their living by making filters that let through
only certain wavelengths. It is a real art and both Chroma and Omega should be
complemented for these filters.  However the ability to use a slit to build your
own bandpass filters is truly a fantastic achievement and also  very useful for
optimizing performance. The cutoff is better defined than a conventional band
pass filter. You have the control of building your own filter that has a sharper
cut off and better liaght transmitted.  The Bandpass filter together with
sequential scanning allows one to control the emitted light and thus you can
optimize  the light gathering efficiency of the system. It is really a better
system.
If you understand dichorics and bandpass filters used with flow cytometers,
Confocal microscopes, microscopes  and other laser based equipment your will see
the fantastic achievement in design that this Leica SP head offers. Being a
government employee I can not recommend any commerical equipment, but I do
appreciate technological performance.
Bob Zucker

Robert M. Zucker, Ph.D
U.S. Environmental Protection Agency
National Health and Environmental Effects Research Laboratory
2525 NC Highway 54,  MD 72
Research Triangle Park, North Carolina, 27709
tel: 919-541-1585 fax 919-541-4017
e-mail: [log in to unmask]