The photographer Weegee used to bring his camera with infrared film and an infrared flash bulb into darkened movie theaters and photograph the audience behind him. Back in the 40s!
Seems like a good idea. I guess the invisible light provides high-resolution luminance data, and the low-resolution visible shot provides the chroma. Since our eyes are more sensitive to luma than chroma, the image is not degraded much compared to a "correct" exposure.
And, since the chroma is degraded, it automatically gives the images that magazine-cover "beauty blur" effect.
Soft focus is spherical lens abberation, something you would usually want to avoid.
Correct, people normally avoid soft focus in the luminance curve. Running the chroma curve(s) through a low-pass filter, however, is the "Make My Logo Bigger Cream"[1] of the commercial photography world.
This process merges a UV/IR photograph with an ambient light visible photograph. However, if you want to take a photograph of someone in the dark they're going to end up looking like the bogeyman.
It's not supposed to be night vision. All I want out of a digital camera is the ability to take hi-res indoor photographs without flash. Consumer-level cameras have modestly-sized CCDs that can't gather enough light fast enough indoors, so the picture is either noisy (not enough light gathered) or blurry (exposure is too long). This aims to remedy the former by using the UV/IR photo to smooth out the noise.
A fast lens might help (if you're into SLRs). f1.8 50mm prime is cheap, though anything faster will cost you.
What he means with 'fast lens' is a lens with a large aperture so that more light reaches the film/sensor in a shorter time.
There is nothing inherently 'faster' about the lens, it is just a figure of speech.
You also have to note that the person will be in the dark. Their eyes will look different than they would in normal light conditions. There's no way to get pictures in the dark that look exactly like daytime pictures, only rough approximations.