 |
Objective Heater System
The Problem
When live-cell imaging requires
the use of high numeric aperture lenses, it is necessary
to control the temperature of the objective as well. This
problem exists because the optical coupling medium (oil,
glycerin or water) acts as a thermal coupling medium and
draws heat away from the specimen. The thermal mass of a
fluid coupled objective is overwhelming when compared to
the thermal mass of the cells. Unfortunately microscope manufacturers
do not offer temperature controlled objectives; nor do they
consider the need for thermal regulation in the design of
their objectives. Bioptechs has developed and patented a
product that solves this problem for the majority of immersion
objectives.
The Solution
To eliminate this thermal
gradient, Bioptechs offers a patented Objective Heater® System
which includes a heater/sensor and an electronic
controller. The heater/sensor is comprised of an
adjustable thin-film heating band which surrounds
3/4 of the diameter of the upper region of the central
retracting tube of the objective. A surface probe
thermal sensor positioned in the gap formed between
the ends of the heating band measures the temperature
of the objective. This heater/sensor assembly is
supported on an adjustable metal mounting to fit
objectives ranging from 17 to 35mm in diameter.
The heater loop requires
a minimum of 3.5 to 6mm longitudinal, physical contact with
the cylindrical objective surface depending on which objective
heater is required. In some cases there may be a decorative
collar on the objective that must be removed in order to
permit adequate surface contact. Depending on the objective,
it may be necessary to invert the objective heater and mount
the objective upside down for optimal thermal transfer to
the lens of the objective. It may also be necessary to isolate
the objective from the nosepiece turret for proper objective
temperature regulation.
Additional options are available
for your objective which can help you heat the objective
more efficiently, or perhaps if you would like to cool
the objective that option is also available.
Key features of the Bioptechs Objective Heater
Specifications
The Controller is specifically designed to slowly
heat the objective over a fifteen minute warm-up
period then hold the objective at the set point
value within 0.2 degrees C. The Controller operates
from ambient to 50 degrees C and has special
safety circuitry which utilizes a 0.9 degrees
C error window to shut down the controller and
sound an alarm if, for any reason, the temperature
of the objective deviates after it has reached
set point. A user calibration test is also built
in to the controller.
| Objective diameters |
17mm
to 38mm |
| Sensor |
Thermistor |
| Temperature
range |
Ambient
to 43°C 1.3 Watt |
| Temperature
stability |
±0.2°C
Typically |
|
Thermographic image of a Bioptechs
Objective Heater
Visible light image of a Bioptechs Objective Heater
Notice the temperature distribution
in the following locations: nosepiece, bottom of objective,
region above heater band, and top of objective. Power
consumption after equilibration is 1.3 watts.
The point is that, unless you warm the entire
microscope, the microscope will always act as
a heat sink with respect to warming the objective.
You can expect a small thermal gradient. All
objectives have different thermal profiles. Therefore,
it is imperative to efficiently transfer heat
to the core of the objective and prevent excess
heat from radiating from the heater-band. This
is exactly what the Bioptechs Objective Heater
does!
Not sure what heater to use?
If you have an objective
that you are not sure how to heat you have a
few options:
- You can check
this list for your
objective and take note of the proper band size
to fit your objective.
- You can use this
reference page to measure your objective and select the
appropriate heater yourself.
- You can send your
objective into Bioptechs to
have it sized, photographed and thermally profiled.
If your
objective has a decorative collar which prevents
an efficient heat transfer, it will need to be
removed. You can do this yourself with the aide
of a special objective wrench
and plier set available
from Bioptechs or send in your objective and
Bioptechs will remove it for free!
Optional Accessories for the Objective Heater
|
|
Demonstration
Video (25.3 MB)
PDF
thermographic images of Bioptechs products. (340 K)
Special Note:
Although there have been no studies relative to the effects of
thermal cycling of objectives between ambient and 37 degrees C,
Bioptechs recommends storing the warmed objectives in a constant
temperature enclosure when not in use.
The Boekel desktop incubator
is well suited for this application as well as a convenient place
for temporary storage of specimens or media near your microscope.
When using the Bioptechs Objective Heater, Cargille type 37 Immersion
oil is highly recommended to optimize the objective's PSF.
This
oil is formulated to have a refractive index of 1.515 at 37 degree
C (Part #150825). This is an ideal optical coupling medium for
in-vitro, live-cell imaging. (not for in-vivo use) |
|
