A little info on what this means and some example pictures
Comparison of an Infrared picture vs. a RGB picture on the basis of a phtograph of Vienna by night. Pay attention to the fog in the distance. (Drag the vertical bar to compare the photos)
Recently I modified my Olympus Pen E-PL1 by replacing the so-called Infrared cut-off filter with a piece of ordinary glass. This glass-filter blocks Infrared light from reaching the sensor preventing the sensor from “seeing” other light than human visible light preventing pseudocolored images from being captured. Since the sensor is very well capable of capturing Infrared light, removing the Infrared cut-off filter enables the camera to see NIR (near Infrared) light.
So now I can take pictures with an extended spectrum of light. More precisely the normal visible spectrum (RGB) plus near Infrared (NIR). If I want to take a picture of just the NIR spectrum I have to use a so-called Infrared passing-filter that allows only Infrared light to pass and blocks out normal visible light.
Typically one would use a professional IR pass-filter such as a Hoya R72 which blocks wavelengths below 720 nm. This is a wavelength at the end of the human visible spectrum so it may appear dark red when looking through the filter a light source such as a light bulb. There are other filters that block everything below different wavelengths. For instance a quick ebay search turned out that 720 nm, 760 nm, 850 nm and 950 nm are commonly available filters.
I on the other hand have no such filter on hand so I used a piece of Perspex 962 which is a PMMA (aka Plexiglass) sort that appears black to to the human eye but is transparent for Infrared light with wavelengths greater than 750-800 nm. Therefore an Infrared pass-filter with inferior optical grade but good enough for testing the camera.