objective heaters for fat, ribbed objectives?

[Stanislav Vitha-2]

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We have a new Leica SP8  inverted confocal system and a Tokai-Hit stage top incubator with an objective heater, which is a Velcro strip that should wrap around the objective.
I have not played with the incubator and heater much yet, but with our 25x multi-immersion objective, the heater strip is too wide to go around the smooth part of the objective barrel, so I am left with available surface that is ribbed/knurled, so the heater does not make much contact with the objective.  I was curious to hear how you objective heater gurus deal with this issue -  is this going to work anyway (my initial attempts suggested that it does not), or do you improvise to make the heat transfer better?  I considered bunching some aluminum foil around the objective, or slipping a foam sock over the objective on top of the heater, but there must be a better way.  I wish I could purchase a version of the objective that has a smooth surface.

The heater does not fit at all on the 40x/1.1 water immersion lens with motorized correction (heater strip is too wide)- if you have one of those lenses, do you use them with a heater  (which one?), or do you have a microscope enclosure?


Thanks in advance!

Stan Vitha
Texas A&M University
Microscopy and Imaging Center

[Craig Brideau]

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On Wed, Feb 20, 2019 at 4:55 PM Stanislav Vitha <[hidden email]> wrote:

>  the heater strip is too wide to go around the smooth part of the
> objective barrel, so I am left with available surface that is
> ribbed/knurled, so the heater does not make much contact with the
> objective.  I was curious to hear how you objective heater gurus deal with
> this issue


Get a narrower heater strip to fit the smooth part of the objective. This
will probably be much easier than trying to modify the objective.

Craig

[Dan Focht]

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Stanislav

You have brought up a subject that I have dealt with to the nth degree.
You are correct that it is necessary to transfer heat to the objective at the most efficient location and method possible. The fact that this objective has two correction collars and no direct access to the “core” does make it more challenging.
I find that the Velcro heating band is the least effective method of attempting to warm an objective because;
1. The thermal transfer efficiency is very poor.
2. That type of warming device does not incorporate the objective’s thermal profile into the regulation.
3. These things are usually PID controlled which takes a long time to reach stable setpoint and they tend to over and under shoot until it figures it out.
As for the poor thermal transfer efficiency here is a point of reference. When heated efficiently it only takes around 2 watts. Therefore, any additional wattage applied that does not go into the objective ends up radiating outward from the heater and convecting upward. Talk about an unintended consequence!

The best location on that objective to transfer heat is through the base, after the sleeve with the writing on it is removed to expose the “casing”.
The reason I recommend this is that the external surfaces of that objective do not transfer heat well, as you have already found out. The problem is that the sleeve, at the base where the writing is, has an airspace between the casing of the objective and the sleeve. Therefore, the sleeve surface is not an optimal surface for heat transfer. The good news is that your objective can be accurately warmed with the Bioptechs Objective Heater System. After the sleeve is removed (it snaps off with the right tools) the Bioptechs, narrow yet high efficiency, heater band is secured around 3/4 of the diameter of the exposed cylindrical casing surface. A temperature sensor is simultaneously held in direct contact with the objective within the remaining 1/4 gap between the ends of the heater band. This way the control loop is reading the actual temp of the objective to include the thermal propagation profile of the objective and to compensate for the heat sink effect of the nosepiece. BTW, sometimes, with difficult to regulate objectives, we use a thermal spacer to reduce the thermal influence of the nosepiece as well as the other non-heated objectives. Our system comes up to set point, locks on, and remains steady within 0.1 degree C in about 15 minutes.
Here are several links to YouTube videos on how to remove the sleeve on Leica Objectives as well as a few other relevant demonstrations.

https://www.youtube.com/watch?v=d82rHKZKU5M <https://www.youtube.com/watch?v=d82rHKZKU5M>
Removal of the sleeve.
I don’t think Leica is happy I show this but if you want efficient thermal control you have to transfer the heat efficiently to the core!
If you don’t have the tools you can send the objective to us, we will remove the sleeve for free.

https://www.youtube.com/watch?v=QnVLH4sqPc4 <https://www.youtube.com/watch?v=QnVLH4sqPc4>
Unheated objective influence on specimen temperature in real time

https://www.youtube.com/watch?v=5sL5uIqtKCo <https://www.youtube.com/watch?v=5sL5uIqtKCo>
Heated objective in nosepiece demonstrates heat loss without a thermal spacer.

I hope this helps.  Feel free to call if you want to discuss this more or give it a try.

Dan


Dan Focht
Bioptechs, Inc.
3560 Beck Rd.
Butler PA 16002
V724-282-7145
F724-282-0745
Toll Free 877 LIVE-CELL (548-3235)
[hidden email] <mailto:[hidden email]>


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We have a new Leica SP8  inverted confocal system and a Tokai-Hit stage top incubator with an objective heater, which is a Velcro strip that should wrap around the objective.
I have not played with the incubator and heater much yet, but with our 25x multi-immersion objective, the heater strip is too wide to go around the smooth part of the objective barrel, so I am left with available surface that is ribbed/knurled, so the heater does not make much contact with the objective.  I was curious to hear how you objective heater gurus deal with this issue -  is this going to work anyway (my initial attempts suggested that it does not), or do you improvise to make the heat transfer better?  I considered bunching some aluminum foil around the objective, or slipping a foam sock over the objective on top of the heater, but there must be a better way.  I wish I could purchase a version of the objective that has a smooth surface.

The heater does not fit at all on the 40x/1.1 water immersion lens with motorized correction (heater strip is too wide)- if you have one of those lenses, do you use them with a heater  (which one?), or do you have a microscope enclosure?


Thanks in advance!

Stan Vitha
Texas A&M University
Microscopy and Imaging Center