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All,

Having been involved in the lighting industry from a commercial standpoint I
wanted to respond to this thread in an unbiased and independent experienced
voice.  

As has been previously mentioned, there are many areas of the spectrum in
which solid-state solutions have surpassed HBO in intensity at the sample
plane.  I completely agree with the assessments that there are many
components that go into building an illuminator and therefore many sources
of light loss in the systems on the market.  Key to any measurement of power
is how much light is delivered to the sample, so if anyone does take up the
offer to compare light sources, measurement of mW//cm^2 at the sample plane
will provide the best indication of the total performance of a light source
on a microscope.  That being said, one must make sure that the excitation
filters used with solid-state sources are matched to the peak of the source
and not simply use off the shelf filters and expect them to perform optimally.

There has been mention in this thread of the gaps produced when using
multiple sources and combining them into a shared collimated beam.  As has
been stated, in general, increasing the number of input sources decreases
the overall throughput of light in the system as source combining optics can
be lossy and will cut the overall intensity of any single source that could
be coupled to the microscope.  One solution that has not been mentioned in
this thread is the 120-LED from Lumen Dynamics.  The 120 LED overcomes the
limits of combining multiple sources by using a high intensity white LED
source.  This product, according to the LDGI website, covers wavelengths
from 370nm all the way out to 700+ nm with reasonable intensity.  While HBO
may be brighter at some wavelengths versus the 120-LED, rarely are these
sources, HBO or solid-state, used at max power especially in live cell
applications.

I would suggest that the 120-LED be included in whatever tests come from
this thread as it is a unique product from the standpoint of how the white
light is generated for fluorescence applications versus the other solutions
on the market that combine many sources.

As for the overall performance of all solid state products mentioned thus
far in this thread, one should consider the following: every mid to high end
solid state source produces multiple times more power than 175W xenon at the
sample plane at all wavelengths greater than 360nm and all the way out to
the NIR.  If anyone has experience using xenon as their primary source, I
hope this puts the current state of solid-state illuminator intensity into
perspective.   Bottom line is for most applications, the benefits in cost of
ownership, stability and overall function have the solid-state solutions
greatly out-perform their HBO counterparts with an additional benefit being
that solid-state sources are a green solution and they eliminate the threat
of mercury contamination due to improper disposal or explosion of mercury
burners.

Ben















On Tue, 5 Nov 2013 12:56:42 -0500, Philip Oshel <[log in to unmask]> wrote:

>*****
>To join, leave or search the confocal microscopy listserv, go to:
>http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
>*****
>
>All,
>
>I had this question put to me by a new faculty member, and don't have a
>ready answer:
>"Is there a ballpark percentage for how much less bright an LED vs a
>standard mercury lamp light?"
>This is for regular epifluorescence, not confocal.
>
>This is in the realm of arm-waving over a picture of beer (a good, dark
>stout), ignoring brands, how old the Hg bulb is, ex/em cubes, which part
>of the spectrum is used, and all that. Personally, I'd think the answer
>is more like, "Doesn't matter, the dimmer system is still too bright to
>use all the available light and not damage the specimen." But ... ?
>
>Phil
>--
>Philip Oshel
>Microscopy Facility Supervisor
>Biology Department
>024C Brooks Hall
>Central Michigan University
>Mt. Pleasant, MI 48859
>(989) 774-3576