Well now you can, with a new technology called MSX.
MSX stands for Multi Spectral Dynamic Imaging, an exclusive image enhancement technology now available on several infrared cameras. This new technology is based on a unique onboard processor that provides extraordinary thermal image details in real time. MSX incorporates real-time thermal video augmented with visible spectrum definition. It produces exceptional thermal clarity to highlight exactly where the problem is. MSX ensures easier target identification without compromising radiometric data. The quality of the thermal images is excellent. There is almost no need any more for a separate digital image; MSX embosses digital camera detail onto thermal video and stills.
How does it work?
An onboard processor continually processes the visual channel and extracts only the visual detail from the visible channel. That visual detail is then added to the thermal image information. Unlike many thermal fusion technologies, the thermal information is not diluted at all, it is just augmented with visual detail not apparent in the thermal image. The result is an incredibly robust and fully radiometric thermal image displaying details and making it easy to know what is being viewed and where problems lie. See this video.