Seeing things in another light

Although we began this chapter by presenting Eulerian video magnification as a useful technique for visible light, it is also applicable to other kinds of light or radiation. For example, a person's blood (in veins and bruises) is more visible when imaged in ultraviolet (UV) or in near infrared (NIR) than in visible light. (Skin is more transparent to UV and NIR). Thus, a UV or NIR video is likely to be a better input if we are trying to magnify a person's pulse.

Here are some examples of NIR and UV cameras that might provide useful results, though I have not tested them:

• The Pi NoIR camera (http://www.raspberrypi.org/products/pi-noir-camera/) is a consumer grade NIR camera with a MIPI interface. Here is a time lapse video showing the Pi NoIR renders outdoor scenes at https://www.youtube.com/watch?v=LLA9KHNvUK8. The camera is designed for Raspberry Pi, and on Raspbian it has V4L-compatible drivers that are directly compatible with OpenCV's VideoCapture class. (For instructions on setting up the drivers, refer to the section Setting up the Raspberry Pi Camera Module in Chapter 1, Preparing for the Mission.) Some Raspberry Pi clones might have drivers for it too. Unfortunately, Raspberry Pi is too slow to run Eulerian video magnification in real time. However, streaming the Pi NoIR input from Raspberry Pi to a desktop, via Ethernet, might allow for a real-time solution.
• The Agama V-1325R (http://www.agamazone.com/products_v1325r.html) is a consumer grade NIR camera with a USB interface. It is officially supported on Windows and Mac. Users report that it also works on Linux. It includes four NIR LEDs, which can be turned on and off via the vendor's proprietary software on Windows.
• Artray offers a series of industrial grade NIR cameras called InGaAs (http://www.artray.us/ingaas.html), as well as a series of industrial grade UV cameras (http://www.artray.us/usb2_uv.html). The cameras have USB interfaces. Windows drivers and an SDK are available from the vendor. A third-party project called OpenCV ARTRAY SDK (for more information refer to https://github.com/eiichiromomma/CVMLAB/wiki/OpenCV-ARTRAY-SDK) aims to provide interoperability with at least OpenCV's C API.

Good luck and good hunting in the invisible light!