DNR's Deep Liquid cooling Technology
Scientific cameras are very delicate devices which designed to give powerful, clear,
sharp and accurate images. These images are the result of a concert of many
electronically components which the camera made up of.
The activation of electronically components, especially in CCD scientific cameras,
create two major kinds of noise (the gritty look of images), which combine to place
the lower limit of the CCD ability to detect faint light sources. In other words, as long
as the camera produces more electrons than is produced by photons (which cause the
signal from a sample) it can be defined that the sample signal is covered by the
background noise.
Camera noises
In general, scientific cameras generate thermal noise and readout noise caused by the
operation of the electronics on the chip. Because of that, the mission is to eliminate
unwanted sources of electron production. Accomplish this goal results in more
sensitive to the remaining source of electron production, therefore from the biological
sample. Improvement of this sensitivity has major impact of the scientific image
performance by the scientific cameras.
One of the noise kinds called Dark Current. This noise is thermally generated
electrons in the sensor itself. All scientific cameras have dark current noise, which can
bring to pixels to be filled by electrons in a few seconds, even in the absence of light.
Dark noise is most evident as “hot” pixels (white dots) in images. The solution for
this phenomenon is to cool the scientific cameras, which bring to sensitivity increased
and allow longer exposures period (the resistance of the pixel elements increases as
the temperature is reduced). In fact, for every 7°C of additional cooling, the dark
current noise is reduced to half. For example, cooling the scientific cameras sensor
from 25°C down to 0°C results in an eight-fold reduction in dark current.
The second noise kind called read-out. The reason for this noise is in the camera
amplifier and may be viewed as "toll" that must be paid for reading the stored charge.
The solution for this phenomenon is technically in the camera.
As mentioned before, to overcome the Dark Current noise, the camera has to be
cooled. There are several cooling system types, which all based on the first law of
thermodynamics: Energy can be changed from one form to another, but it cannot be
created or destroyed. Energy can be converted from one form into another. In essence,
the heat can not be destroyed, we can just transfer it from the scientific cameras to
another component.
Heat transfer modes
In order to transfer the heat, there are three general modes of heat transfer. Some heat
transfer configuration can be duplicated using multiple methods, but every cooling
system uses these same basic processes:
1. Conduction: Conduction is heat transfer by means of molecular agitation
within a material without any motion of the material as a whole.
2. Convection: Convection is heat transfer by fluid mass motion. Like heated gas
or liquid, that moves from the heat source, carrying energy with it.
3. Radiation: Radiation heat transfer is energy transport by emission of
electromagnetic waves or light from a surface or volume.
Image courtesy of www.geography.hunter.cuny.edu
Camera cooling
In order to avoid the camera noise, the heat must be eliminating. There are three main
possibilities for scientific cameras cooling:
1. Air ventilation Heat which generated from the camera sensor is transferred
into a metal heat sink, where a fan blows air across its wider surface area. This
cooling option is limited, as air absorbs and transfers heat very slowly.
Improving it can be done by run the fan at a higher speed, but, high
performance has become equated with high noise. As systems continued to be
upgraded, required heat sinks got larger and louder.
Image courtesy of Koolance (http://www.koolance.com/technical)
2. Peltier elements (thermoelectric cooling)
In 1834, a scientist called Peltier discovered an effect, now known as the
"Peltier effect", that if you take two dissimilar metals that are connected at two
different locations (junctions), and apply a voltage, this causes a temperature
difference between the junctions. This results in a small heat pump, later
referred to as also known as a thermo-electric cooler (TEC). A peltier cooler is
a cooler that uses a peltier element (TEC), and a powerful heatsink/fan
combination to cool the TEC. The major problem with this cooling device is
high power usage and high power dissipation. Due to these disadvantages, the
cooling system will be expensive to run, and not very eco-friendly. It will also
be needed powerful (and thus loud) fans, because of the large power
dissipation. The biggest advantage of this kind of system, it allowed cooling
below ambient temperature.
Courtesy of the "THE HEATSINK GUIDE" (http://www.heatsink-guide.com)
3. Liquid cooling
Cooling systems which based on liquid, works by fluid movement in a closed
system, through the camera sensor, removing excess heat, and while doing it
the liquid temperature is raising. Now, the coolant must be returned to set
point temperature by flowing through a heat exchanger – a device that
transfers heat from one liquid to another. An example of heat exchanger is a
radiator in a car. The hot fluids in the radiator are being cooled by flowing air
over the radiator surface. Than, when the fluid is cool again, its going back
through the elements and so on. When temperature below 00C is needed to be
set in the cooling system, an anti freeze (usually Ethylene Glycol) is added,
and it reduce the freezing point of the coolant to around -34°C.
In the cooling system of CCD camera, there is a use of special radiator kind,
which called Brazed Louver Fin. In this kind of radiator there is a web foil
(Louver fin) between parallel liquid channels, which provides tremendous heat
dissipation. In order to cool the CCD sensor below zero, a special kind of
ethylene glycol is added to the fluid. Although more expensive to produce this
radiators, but the performance are significant.
Image courtesy of Koolance (http://www.koolance.com/technical)
Optional coolants
There are several coolant possibilities to use in the cooling devices, and the
coolant selection is being done regarding to the specific heat capacity and
thermal conductivity.
Thermal Conductivity defined as the heat amount that a material can carry in a
time unit. The conductivity measured in W/m K units. This unit describes how
many Watts of heat can be conducted through a one meter thickness of
preferred material with a one Kelvin degree difference between one ends to
another. From the following table we can conclude that water (after mercury)
conducts heat the fastest. Its can conducts heat about 30 times greater than that
of air. This is one of the reasons that water is the preferable coolant in cooling
devices.
Specific Heat Capacity
Characterized as the ability of a material to hold heat as it changes in temperature.
The heat capacity measured in kJ/kgK units, which describes how many kilojoules of
energy are required to change the temperature of one kilogram of preferred material
by one Kelvin degree.
Although there are many other factors involved, here you have the basic foundation of
a liquid cooling system.
DNR cooling device
As liquid cooling devices are becoming widespread, especially in scientific fields,
innovations are always needed.
In general, cooling systems looks simple - coolant is pumped through a cooler,
absorbs heat, and it's cooled back down with a radiator. But in order to produce
images in scientific grade, the design become more complicated.
1. Deep Liquid TechnologyTM Pump
the heart of the liquid cooling device is the pump. therefore, the pump
designed to work perfectly, during long time periods. ). It means you can
always use it, shut it down and back it with faith.
2. Deep Liquid TechnologyTM Electricity
As we all know, contact between water and electricity must be eliminate. In
order to achieve it, each component design to fit perfectly the next and all the
system is being clamped. By that, high amount of physical pressure can be
handling during long time periods – as requested in several biological
experiments.
3. Deep Liquid TechnologyTM protection
We all know that the cooling system is working well. But, what will happen if
something goes wrong? The camera sensor will heat up, the coolant will easily
absorb the additional heat, but slowly and the coolant temperature will
increase. Hot camera sensor first leads to create distort images, and if the
temperature will increase, the sensor will destroy. In order to protect the
camera from heat, DNR have built a safety software feature. Once the camera
temperature rise above 0OC absolute, a warning message is popped up and the
user can not take images.
4. Deep Liquid TechnologyTM Corrosion avoidance
Corrosion can be define as chemical or electrochemical reaction between a
material, usually a metal, and its environment that produces a deterioration of the
material and its properties. While corrosion is occurred, it damaged the system
and the temperature of the camera will raise. Therefore, distilled water should be
used. DNR coolant also features anti-corrosion additives that are commonly used
in the engineering field to avoid reactions.
The complicated and efficient DNR Deep Cooling TechnologyTM device is design
With a key emphasis on silence, professional quality and Reliability, in order to
give the best scientific results to the user.
Bibliography:
1. Spring K.R."Scientific imaging with digital cameras", Biotechniques 2000,
29, 70-76.
2. Inoué, S.; Spring K.R. "Video Microscopy; the fundamentals" Plenum
Press, New York, 1997
3. Russ, J.C. "The Image Processing Handbook" CRC Press,
Boca Raton, Florida, 1995
4. McMurry J.; Fay R.C. "Chemistry" Prentice Hall, New Jersey, 2003
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