Did you ever wonder how your TV remote actually tells the television to change the channel or turn down the sound? Have you ever wondered how satellites can see through clouds and give an image of the ground underneath? And those night vision goggles, just how do they work?
These devices and hundreds of others rely on infrared light, light that we can’t actually see, to perform their functions.
The light you can’t see
Infrared is a form of electromagnetic energy just as are radio waves, microwaves, ultraviolet rays, X and Gamma rays and visible light. These forms of electromagnetic energy make up the electromagnetic spectrum which is measured by the wavelength that each form has.
For example “visible light” which consists of the 7 primary colors has a wavelength range of 390 nm – 470 nm. Actually the term visible light is a misnomer because all light is visible if it is perceived by an appropriate receptor. Our human eyes are limited to “visible light” but a bee for example can see ultraviolet light. Infrared has a wavelength range of 700 nm – 30,000 nm which is well outside human detection.
Detecting invisible light
Infrared receivers allow infrared light to be used in hundreds of ways. For example in the case of your TV remote, when you press the channel changer an infrared light is emitted and picked up by the receiver on the TV set. This light is sent in pulses and the pulses are the equivalent of binary code. The receiver gets the infra red pulses and passes them to the microprocessor that translates the binary code into a command (switch to channel 4) and performs the function.
The satellite photos and the night vision goggles both work on a form of thermal imaging. Heat is one of the easiest forms of electromagnetic energy to detect. A satellite equipped with a thermal imaging camera can “see through the clouds” by detecting the thermal energy of the objects below and assigning a range of colors based on the strength of the heat signature. The net result is a colorful image that you typically see on a weather map. Goggles work much the same way but detect the lower range of infrared rather than true thermal imaging.
Capturing invisible light as art
While there are hundreds of industrial and scientific uses for infrared, the whole “seeing the invisible light” phenomena started in the early 1900s when photographers first developed a working infrared process.
Infrared photography remained the domain of a small number of professional photographers for years due to the time consuming and complex process that was involved in creating a single image. Today, thanks to digital camera that can become exclusively an IR camera, infrared photography is growing in popularity.
Infrared photography involves excluding visible light from entering the lens by use of a filter or a true IR camera, and then processing the image in Photoshop to get the desired effect. IR photographs depend greatly on the skill and creativity of the photographer both with the camera and with Photoshop. The results however are breathtaking and well worth the extra effort.
Melissa Cameron is a full time bookkeper during the day and a full time mother of three when she gets home. In the little free time she does have she loves learning how to improve her infrared photography skills.