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Optical Microscopy with Instec Devices
 
When using an Instec hot and cold stage on a microscope there are some special considerations to be aware of. The hot and cold stage typically consists of a sample chamber with a heating and cooling block on which the sample or its holder rests. The viewing aperture of the hot and cold stage, which provides optical access to the sample, is relatively small due to consideration for temperature uniformity. If a microscope X-Y stage is used to move the hot and cold stage, the sample view will be blocked once the optical pass is beyond the hot and cold stage's viewing aperture. Thus, it is better to move the sample inside the hot and cold stage rather than the hot stage itself. Many Instec hot and cold stages feature convenient sample side loading and unloading, without opening the hot stage covers. The manual movement of a sample sometimes is insufficient. Therefore Instec offers optional X-Y  Micropositioners for many of its hot and cold stage models, which feature micrometer heads with 10μm resolution.

Since a microscope X-Y stage is not particularly useful when using a hot and cold stage, it is often better to get a rotational stage for the microscope. A microscope rotational stage should almost always be used for a polarizing microscope (even if a hot and cold stage is not being used) due to the directional nature of polarization.
 
Additionally, there are a couple of specifications for the microscope to keep in mind. In particular these include the working distance of the objective, and the working distance of the condenser.

The objective working distance is the distance between the front lens of the objective and the focused specimen. Due to the need for thermal control and isolation of the specimen in a hot and cold stage, there may be several millimeters between the top of the stage and the specimen itself. In this catalog we term this distance the "minimum objective working distance " or "minimum working distance" . Clearly if the working distance of the objective is shorter than this distance, a focused image cannot be achieved. Instec puts considerable effort in keeping its operating working distances as small as is practical. However if necessary, a shorter working distance can be achieved by removing the outer windows of the stage. Special attention is needed when operating a stage in this manner as not only will the removal of the outer window compromise the thermal isolation of the stage, but it will also bring the microscope objective into close proximity of the heater elements. Please be aware that on some stages these temperatures can reach over 600°C and could therefore damage the objective.

While not as obvious, the condenser working distance is also an important specification when using hot and cold stages together with microscopes.
 
Modern microscopes generally use what is termed Kohler Illumination, named after August Kohler who first introduced the technique in 1893. In this arrangement a magnified image of the light source is formed at the aperture diaphragm of the condenser when the field diaphragm of the microscope is imaged at the sample position. This separates the image of the light source from that of the sample, increasing the uniformity of the light at the sample position and allowing the condenser's aperture to be used to control the numerical aperture (NA). If the condenser's position is not correctly adjusted, the intensity of the light reaching the sample is reduced, the uniformity decreased, and worst of all stray light can show up as glare. Therefore to get the most out of a high quality microscope, it is important that the condenser working distance be large enough to reach the sample when placed in the hot and cold stage. If needed, a long working distance condenser may be available from microscope dealers. Instec also sells these items with a universal dovetail fitting compatible with most upright microscopes.
 
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