 Peltier Cooling
The Pixera Penguin digital camera system incorporates state-of-the-art temperature reduction techniques to increase camera sensitivity while decreasing the thermal noise which is inherent in all CCD-based digital
imaging systems.
The Pixera Penguin utilizes a high-resolution CCD (Charge Coupled Device) as its imaging sensor. An electronic memory that can be charged by light, CCDs can hold a variable charge, allowing it to record
variable shades of light.
In order to capture low-light-level subjects (i.e. darkfield transmitted/reflected, fluorescence, polarized light,
and high magnification), the exposure time of the camera must be increased in order to achieve the necessary level of sensitivity for imaging the specimen. Unfortunately, the low light levels, coupled with the longer
exposure times, introduce a phenomenon known as dark current.
Dark current flows in a photodetector when it is not receiving any light. This is basically charge which accumulates in the CCD pixels due to thermal noise. In general, it increases as temperature rises. All CCD's,
at some level, exhibit the occurrence of dark current. The effect of dark current is to produce an additive quantity to the electron count in each pixel. At room temperatures, the dark signal is such that, under long
exposure times and sufficiently low-light conditions, the electrons generated from the camera subject would be overwhelmed by the number of dark-signal electrons.
In order to reduce the negative effects of dark current, the Pixera Penguin uses a Peltier thermoelectric (TE) cooling module to keep the CCD itself cold (about x degrees Centigrade). Using cooling techniques based
upon Peltier cooling elements, the chip temperature has been dramatically lowered, leading to low thermal electron production rates and a vastly increased signal-to-noise ratio (S/N). Using this technique, the Penguin
is capable of exposure times of up to x minutes while minimizing the effects of thermal noise.
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