Andor Technology Neo sCMOS, Руководство по оборудованию

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FEATURES & FUNCTIONALITY
Neo
SECTION 2
Page 26
2.2.2 - Effect of TE cooling on noise floor
The ultra-low value of 1 electron RMS read noise available from sCMOS cameras is entirely unprecedented,
and dramatically outperforms even the best CCD to date. Read noise is an important contributor to the noise
floor detection limit of a camera, but the noise associated with thermal signal, dark current, should never be
overlooked. In CMOS cameras especially, even modest exposure times can result in a significant increase in
dark noise. Furthermore, since scientific CMOS cameras have a much lower read noise baseline, then the
percentage increase in dark current can be proportionally larger. The Andor Neo sCMOS platform is unique in
the market in that it is the only scientific CMOS camera to offer the level of deep thermoelectric cooling
necessary to minimize the detrimental influence of dark noise. Figure 6 below shows theoretical plots of noise
floor versus exposure time, at three different cooling temperatures, +5ºC, -30ºC and -40ºC. The parameters
used in determining the overall noise floor are based on a typical read noise ‘baseline’ of 1 electrons, combined
with the measured typical dark current of the sCMOS sensor at each of the temperatures. Combined noise is
calculated in quadrature, i.e. using the ‘square root of the sum of the squares method.
Even within the exposure range up to 1 sec, the low noise floor can be notably sacrificed by ~ 75% at the
higher temperature of +5ºC. Cooling to either -30ºC maintains the 1 electron noise floor over this short
exposure range. At an exposure time of 10 sec, the noise floor associated with +5ºC is significantly
compromised to a value approaching 5 electrons, i.e. x5 greater than the read noise, whereas the noise is
maintained to values less than 1.5 electrons with deeper cooling.
For very low light measurements, such as in chemiluminescence detection, it can sometimes be desirable to
apply exposure times up to or greater than 10 minutes. At 600 sec, unless deep cooling is applied, the thermal
contribution to the noise floor would become excessively large, shown in graph (c) as reaching 35 electrons.
Holding the cooling temperature at -40ºC would result in the noise floor being held at a more modest 5 electrons
over this extensive exposure period.
Figure 6: Plots of sCMOS noise floor (read noise and dark noise combined in quadrature) versus exposure time, at sensor
cooling temperatures of +5ºC, -30ºC and -40ºC. Plots are shown over three ranges of exposure time; (a) 0.1 - 1 sec, (b) 1 - 10 sec
and (c) 1 - 600 sec.