How do Infrared cameras work?

Question

Me and my mom had a debate yesterday about how infrared cameras work. My point was that they had a high-sensitivity camera and tinted the infrared color to a minty-green color, which is the opposite and most contrasting. My mum thinks that they shine an infrared torch at the same time as filming with an infrared camera and then tinting the infrared color. Considering that all light is known as white light. no matter what color of filter it looks like, shining a blue flashlight and shining a yellow one both gives off white light. She is always telling me the difference of color and light but is getting confused herself. Plus infrared COLOR is given of from heat proving that you dont NEED an infrared flashlight.

Answer 1

IR is 'off the red end' of the visible spectrum.



All digital camera sensors can 'see' in the IR region ... your mass-market SLR has a filter that stops IR reaching the sensor (since IR would ruin 'normal colour' images). For astronomy use, the DSLR can be taken apart and the filter removed.



Security cameras have no IR filter and 'see' in black& white. Whilst it's true that hot things give off IR radiation, this is quite 'low level' .. so in a security application, IR floodlights are used at night (you may be able to see some of the IR light as a faint glow .. even though the floodlights have red filters that are designed to eliminate any visible light 'leakage')





Generally, the IR camera delivers a digital image is 'black & white' and the 'false colour' is added by electronics to make it easier for the eye to see .. (since the eye is most sensitive to green, that's the colour most often used in 'night vision' equipment)

Answer 2

Infra red light is not visible to humans. In that sense, it does not have a natural 'colour' in the way we would understand it. Some infra red sources (not all) also give off some red light that we CAN see.



It is visible to sensor devices like we have in our cameras.



Infra red radiation is given off by things that are warm/hot.



If we send out a beam of infra red light, its reflection or re-radiation can be picked up by a suitably tuned sensor, just like shining a torch. My infra red security camera has infra red emitting LEDS to send out a beam like a torch. The sensor converts the infra red into an electrical signal that can be displayed at a different frequency that we can see.



If you have access to a video camera, try this experiment: start recording, then point a remote control for a TV/DVD or whatever directly at the camera while recording what you do. Now look at the recording and see what the sensor in the video camera has done with the invisible infra red light.

Answer 3

It works more by 'tuning' the cameras lenses and sensors to the infra red spectrum. (PS all light is not known as white light, that is the combined wavelengths of the visible light spectrum)