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Dear Listmembers (and Colin),
As Colin mentions, there is another CCD with on chip gain available from
Marconi (now E2V). We too have this CCD since we work closely with E2V on
many projects, including custom designed chips. After evaluating the
initial CCD in this product line (the CCD 65), we saw some advantages of the
CCD in terms of raw gain but we decided not to implement this particular
chip due to the very large, non-standard rectangular pixels (20x30 microns).
The largeness eliminates the resolution advantages that the CCD could
theoretically have against an ICCD and the format on the pixels distorts the
image.
The next CCD in this product line is now emerging, the CCD 87 is a step
forward with 16 micron square pixels. We too have a produced a camera based
on this CCD which is available for evaluation by those who are interested.
Once again, this camera does not perform better than our back illuminated
MicroMAX and VersArray camera line since back illuminated CCDs convert 90%
of the photons compared to the abysmal conversion rate of the CCD 87 front
illuminated CCD. The ability of the on chip gain mechanism to raise the
signal over the noise allows the few photons converted to be seen. So for
now, the back illuminated systems will give the best data.
Our feeling is that the best implementation of the on chip gain technology
from Marconi is still to come. They plan to add back illumination to the on
chip gain CCDs. This will be something to look forward to indeed. We will
have this technology as soon as it is available according to E2V.
One other comment on the comparison data, as Colin has done and perhaps
others, I have compared the Cascade to an intensified camera on a one to one
microscope coupler and the ICCD always wins due to the largeness of the
effective pixel (in our cameras, it was about 9:1 pixel area difference).
When we normalize the light per pixel between devices the ICCD is still a
bid more sensitive but not a lot. When we have compared the CCD 65 to the
Cascade internally, again we have seen the area factor collect much more
light (20x30 = 600 square microns vs 7.4x7.4 = 55 square microns, 11:1
ratio). Again, the CCD 87 will still give more light collection but
remember, that is in trade off to resolution. The Cascade is the
combination of high resolution and sensitivity, if you set up the
magnification correctly. This means I would usually do an experiment using
a 60x with an NA of about 1.4 instead of using the 100x.
Again, I would suggest a scientist get in touch with one of our
representatives to get assistance and evaluate the correct technology for
each application. We have the broadest range of choices available to you so
you don't have to go with the fad of the time. Just get the best detector
for your particular applications.
BTW Colin, when you post, it is polite to put COMMERCIAL in the Subject
line to inform the reader list that you have financial interests in the
outcome of the discussion.
Regards,
Mark
Mark Christenson, Ph.D.
Senior Scientist
Life Sciences
Roper Scientific
3660 Quakerbridge Road
Trenton, NJ 08619
Phone (609) 587-9797
FAX (609) 587-1970
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-----Original Message-----
From: Colin Coates [SMTP:[log in to unmask]]
Sent: Thursday, August 01, 2002 8:49 AM
To: [log in to unmask]
Subject: Re: Comparisons of cameras ICCD vs the
Cascade/TI/Marconi, data anyone?
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In response to the 'contrary opinion on L3' of George A. Peeters,
Solamer
Technology Group:
The iXon from Andor Technology is still the only camera that
actually
delivers the true potential of the L3 vision technology. The Cascade
uses
the inferior TI chip, which simply doesn't offer enough gain, and
the
Marconi analogue version is a demonstration camera for the L3 vision
technology, and does not have sufficient cooling. The Marconi chip
does
however provide the necessary gain capability, and the extended
thermoelectric cooling offered by Andor will effectively eliminate
amplified darkcurrent in this sensor.
Therefore, it is not a surprise to me that the Cascade camera
containing
the TI chip did not perform well against your ICCD - the TI sensor
simply
doesn't have the gain performance to amplify the weak signals
sufficiently
above the noise floor! In a recent evaluation of Andor's iXon camera
against a GenIII ICCD system and a Cascade in a Single Molecule
Microscopy
application at Stanford University, the Ixon compared very
favourable
against the GenIII in performance, and the Cascade could not amplify
the
weak signal from the single fluorophores into a detectable signal. A
scientific evaluation (presented recently at SPIE Seattle) of
Andor's
Electron Multiplying CCD technology (based on Marconi's L3 offering)
vs.
ICCD technology can be found on Andor's website (http://www.andor-
tech.com/main_3.htm), and validates the superior QE and resolution
performance offered by this technology over that offered by
intensified
systems.
So, if you really want to the true Electron Multiplying capability
of the
L3 technology, contact Andor.
Best Regards,
Colin
Dr Colin Coates
Senior Scientist
Andor Technology
Tel: +44 (0)28 90237126
Fax: +44 (0)90310792
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