A thermographic camera is a type of camera that creates an image using infrared light. This technology may also be called forward looking infrared (FLIR), or thermal imaging. Unlike normal photographic or video cameras that record the different wavelengths of visible light as pictures, these devices detect invisible, infrared light, also known as heat. In essence, they create a visual representation of heat.
Infrared is electromagnetic radiation with a longer wavelength than visible light. It is therefore invisible to the human eye. Most thermographic cameras are designed to detect these longer wavelengths and to distinguish differing intensity levels of infrared. For example, living creatures typically emit higher levels of infrared than inanimate objects, so they may show up with a greater intensity on an infrared image.
A thermographic camera often creates an image based on the intensity of the infrared waves striking its sensors. The image may show where a heat source is located, and how much heat it is producing relative to the objects around it. Being able to detect higher and lower intensities of infrared may be useful in a variety of fields such as medicine, law enforcement, architecture, and archaeology.
Many of these cameras are monochromatic and vary the brightness of color based on the intensity of the infrared. Others arbitrarily assign different colors to each range of intensity, called false color. Infrared light is not a color because it is not visible light, so a false color thermographic camera assigns colors to infrared levels. Typically, these cameras display white as high intensity infrared; yellows and reds for mid-range levels; and blues for low.
Typically, each thermographic camera carries an infrared detector onboard. The detector allows the computer to create an image by overlaying gradients of light and dark, or false colors. There are two main types of these detectors, cooled and uncooled.
Cooled infrared detectors are usually housed in a sealed case and cryogenically cooled below ambient temperature. These detectors are often highly accurate because neither the ambient temperature nor the device itself can interfere with the heat sensor. This generally allows the camera to receive a precise measurement of the infrared energy in the camera’s line of vision.
Uncooled infrared detectors are not cryogenically cooled, but instead rely on sensors that create a baseline ambient temperature reading. For the most part, if the thermographic camera can base its readings off of the ambient temperature, then it should be able to represent variations in infrared temperature. These cameras are usually not as accurate as the cooled versions, but advances in technology may make them so in time.