thermochromic decay contrast NIR / thermal imaging

thermochromic decay contrast NIR / thermal imaging Video Clips. Duration : 1.15 Mins.

thermochromic liquid crystal foil shows some nice colors within a small temperature range (28-34°C for this foil) and stays black otherwise. What I'm showing here is that during the color changing process taking place as the homogenously pre-heated (35..40°C) foil cools down to room temperature (25°C), minute amounts of additional heat can visibly alter the color changing rate of the foil. By relaxing over a certain temperature range, smaller temperature differences can be resolved than with an equilibrium / transition temperature setup. The foil can also be reset by making contact with a temperature-controlled metal plate from the uncoated side. Thus, optical contrast is created and color differences between irradiated an non-irradiated areas can be seen. A cheap thermal IR (8-12µm) camera could be built using a peltier cooler / heater to reset the foil and set the measurement box to a specific temperature. Since IR lenses (ZnSe, Ge) are expensive and NaCl lenses that could be hand-made are hygroscopic, a mirror lens system could be used. A CCD camera and LED illumination could be used to capture the thermochromic sheet over an interval of 10-30sec and a piece of software could be used to calculate a thermal image. An imaging cycle consists of resetting the foil to 40°C and capturing a set of images or a video of it as it cools down inside a box held at 25..28°C. Thermal image projection and optical observation is done from the same side (bottom of the box looking ...

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