Silicon-based camera sensors exhibit significant sensitivity beyond the visible spectrum (400-700nm). They are able to capture wavelength up to 1100nm. Near-infrared is the portion of the radiation spectrum that ranges from 700 to 1100 nm. Even though this radiation can be captured by silicon, it is usually considered noise and therefore is removed by putting a filter (hot-mirror) in front of the sensor.
Retaining instead of eliminating NIR information improves certain tasks in digital photography and computer vision. Intrinsic properties of the NIR part of the spectrum make the scene sharper and less affected by atmospheric haze. NIR images are also “transparent” to a number of colorants or paints and as such can see through the first layer to reveal the surface underneath. Exploiting the inherent correlation and de-correlation of the different waveband images can lead to improved color rendering and object recognition.