Good question Mr Paulo Araujo ......

No, you do not need additional illumination, except for LED lamps which emit monochromatic visible light only. Conventional incandescent lamps or sunlight will suffice.

You will not get greyscale images, because still your sensor has RGB filters on it (like a Bayers array). These filters pass different portions of the IR light. Mostly your images will appear reddish, because the red filter passes more NIR than the green and blue ones.

There are NIR cameras on the market with no Bayers array (mostly NIR surveillance cams, those with NIR LEDs around the lens), or cameras with an RGBW (W for white) filter array. The first ones give gray images, the second ones give normal RGB and in addition a VIS+NIR channels.

Thanks for your answer Thomas Fischer ! I'll search for this kind of camera to do some tests.

@Thanks Joachim Pimiskern

Dear Paulo Araujo,

Basically when taking the image there are 3 concern:

1. Camera spectral sensitivity

Most RGB camera may have CCD or CMOS sensors. These type of sensors cover the spectral range around 300-1000 nm (Visible range are around 400-700 nm). For RGB camera additional filters were attached to the sensors i.e. R,G,B filters (arranged in an Bayer Filter Mosaic) and possibly UV cut and IR cut filters (covering all). Some monochromatic camera use CCD or CMOS sensor without filter so they cover all spectral range. Like you have mentioned above, it may be possible to take IR image with RGB camera by removing IR cut filter, but you need to check the spectral transmissivity of the R,G,B sensors, which one can capture in IR range, then you can use the corresponding R,G,B channel to get your image.

You can try to search in google images with following keywords:

- RGB camera spectral response/sensitivity

2. Light source spectra

The camera will capture light depend on their spectral range. There are 2 kinds of light source i.e.: Monochromatic and Polychromatic light (mentioned also by Thomas Fischer). If you use RGB camera with UV cut and IR cut filters and then you provide LED which is monochromatic with emission in UV or IR region, then your camera may be unable to capture the image. Polychromatic light source such as halogen lamp and other incandescent lamp may provide broad range of light spectra, however if you camera capture also broad range then the captured information will be biased e.g. it will contain mix visible and IR spectra. Check your light source spectra, camera sensitivity, and filter transmissivity.

3. Object optical properties and image acquisition principle

The last one is about the object you want to capture, if they have strong absorption in IR and you capture with IR camera system they will be dark and vice versa. Image acquisition principle also play a role for example is it normal reflectance based system or transmittance based system.

Hope this information can help a little bit.

Sincerely.

Thanks Dimas Firmanda Al Riza for your answer, I really appreciated it!

Good question Mr Paulo Araujo ......