EMCCD Tutorial
Q12 Does EMCCD technology Age?
It has been observed that EMCCD sensors, more notably in cameras that incorporate
L3Vision sensors from E2V, are susceptible to EM gain fall-off over a period of
time. This phenomenon has been documented by E2V and can be viewed on their web
site. All back-illuminated EMCCD sensors are of this brand and therefore all are
susceptible to EM gain ageing:
‘An
Overview of the Ageing Characteristics of L3Vision™ Sensors’
It is important to note that the ageing effect applies to any EMCCD camera, by any
manufacturer, that incorporates these L3Vision sensors. In Andor’s iXonEM+
range, this corresponds to DU-897, DU-888 and DU-860 models. If left unchecked,
this ageing phenomenon has the potential to significantly compromise the long-term
quantitative reliability of EMCCD cameras. Fortunately, if these highly sensitive
sensors are integrated into intelligently designed camera electronics, ageing can
be minimized and should not present any real problem to the user. Andor Technology
have recognized the ageing issue and are unique in the market to have implemented
innovative measures to stabilize the EM gain on these sensors, ensuring that this
ground-breaking ultrasensitive technology can deliver a prolonged quantitative service
to the user. iXonEM+ cameras have been internally configured to ensure
that the rate of EM gain fall off is significantly reduced under standard operation.
Part of the measures taken has been to invoke real EM gain limits, coupled with
signal intensity feedback warnings (after EM amplification) to ensure that the user
is more restricted in his/her ability to apply excessive EM gain and/or signal.
The EM gain scales offered are more than sufficient to render the read noise floor
as negligible for a given signal intensity and readout speed. These tight user restrictions
significantly reduce the rate of EM gain fall off. Furthermore, Andor Technology
have developed a unique and patented method of user-initiated EM gain self-recalibration.
Even after exercising due care during usage and availing of the above anti-ageing
restrictions, the EM gain may deplete over an extended period of time. The EMCALTM
self-recalibration process is very easily initiated by the user. At the touch of
a button, a routine is triggered that measures EM gain and uses the iXonEM+
in-built temperature compensated RealGainTM scales to reset the EM gain
calibration (if required), to deliver the true values requested on the software
scale – i.e. resetting the factory calibration. EMCALTM stands to markedly
prolong operational lifetime and quantitative reliability of back-illuminated EMCCD
technology, and circumvents the need to return the camera to the factory for recalibration.
It is important and fair to note that EMCCD cameras incorporating sensors from Texas
Instruments have shown rates of EMCCD saturation-induced ageing that are orders
of magnitude slower than those with E2V sensors, exposed to comparable light intensity
and EM gain. In Andor’s iXonEM+ range this refers DU-885 and DV885LC
cameras. Note also that Andor’s LucaEM models contain exclusively sensors
from Texas Instruments.