Infrared Cameras
Introduction
An infrared camera is a non-contact device that detects infrared energy and converts it into a visible light display. The infrared energy is first translated into electrical impulses that are then converted into data for camera display. The image or video formed on the screen is of different colors depending on the intensity of the infrared emission. Most cameras have built-in visible light digital cameras that allow merging of infrared and visual images. There are two different types of infrared cameras; cooled cameras and uncooled cameras. The cooled infrared cameras produce superior image qualities than uncooled cameras but are more expensive. The primary considerations when selecting the type of infrared camera include; whether the picture will be saved for analysis or not, and if the actual temperature of the component is required or merely the temperature difference.
A British astronomer of German descent known as Sir Fredrick William Herschel in 1800 discovered infrared light (National Aeronautics and Space Administration). This happened while he was using a variety of colored filters to observe sunlight when he noticed that some colors passed more heat than others did. He hypothesized that the colors themselves must be producing different temperatures and set out to investigate his theory.
Herschel directed sunlight through a glass prism that dispersed the light in a spectrum. He then used thermometers with blackened bulbs to measure the temperature of each color. The blackening of the thermometers’ bulbs was to increase the bulbs heat absorption abilities. He placed one thermometer in the visible color, and the other two were placed beyond the spectrum as a control sample. He found that all of the colors had higher temperatures than the controls and the temperatures increased from the violet portion to the red portion of the spectrum. Noticing this pattern, he decided to measure the temperature of the region devoid of sunlight just beyond the red part of the spectrum. The area had the highest amount of temperature above all colors of the spectrum. Herschel performed further tests on the rays that he called calorific rays and found that they could be absorbed, reflected, refracted and transmitted in a similar manner as visible light. The discovered light beyond the red light is what is known today as infrared light or radiation. This was crucial because it was the first time that someone proved that there was light we could not see with our naked eyes.
Development of Thermal Imaging
Our vision is limited to only a small portion of the electromagnetic spectrum. Among them is thermal energy that we cannot see because of its longer wavelength than visible light. Infrared cameras expand the portion of the electromagnetic spectrum we perceive and allow us to see and measure the thermal energy emitted from objects. Everything with a temperature above absolute zero including ice cubes emits infrared. Infrared cameras have lenses just like visible light cameras, but their lenses focus on thermal waves only present in infrared energy. The thermal cameras then produce the images of invisible infrared radiation allowing us to see what our bare eyes cannot.
In addition, the infrared cameras can precisely measure an object’s temperature. This is because the higher the object’s temperature, the greater the infrared radiation emitted. The camera gets the temperature of an object from three sources of total heat energy; reflected, transmitted and emitted heat energies. The emitted radiation is what gives the temperature information, and the transmitted energy is usually ignored since most materials are opaque to infrared. However, most low emissivity materials like reflective metals reflect infrared radiation. These materials can cause significantly inaccurate thermal readings if not accounted. This is done through reflected temperature compensation (Kim and Lee). The compensation allows for the input of the ambient background temperature near an object caused by the reflective energy. The value is then used in the computation of actual target object’s temperature.
Advantages of Infrared Cameras
There various advantages associated with the use of thermal imaging technology that is discussed below. The infrared cameras are not affected by visible light and thus can be used anytime be it day or night. This also gives it the ability to be used in all weather conditions including fog and rain.
The cameras can be used from a safe distance because of their non-contactless feature. This makes it deployment in potentially dangerous conditions possible without putting the user in harm’s way.
The infrared cameras are easy to use and record in real-time rather than snapshots with little or no processing time required (Johnson). This allows it to have various application in many industries.
It is also extremely difficult to hide from thermal imaging since it is virtually impossible to mask thermal contrast. This has made a very popular device in security systems.
Disadvantages of Infrared Cameras
The cost of buying the cameras is rather hefty compared to the price of regular visible light cameras. This limits its use to mostly large corporations, educational institutes, and public service.
Despite the fact that it is impossible to hide from the cameras, the thermal images cannot be used for identification purposes. Furthermore, objects with very close temperature ranges can be hard to distinguish using thermal imaging technology.
Finally, not everybody can interpret the images obtained from by the infrared cameras. Analysis of the images requires a certain degree of knowledge, training, and experience especially in situations where the temperature readings are required.
Myths and Facts of Infrared Cameras
The price of infrared cameras has limited their availability to the public. Most people have only had of the technology or seen them in fictional films. This has led to people coming up with several myths concerning the cameras. An example of such a myth is that infrared cameras can be used to see the inside objects and houses, which is a false statement. This is because the cameras only see the surface of an object and the heat it radiates, Therefore, it is impossible for an object to see inside a house since it will pick up the house’s exterior thermal image first. Another myth is that colors of the target object will have an impact on the thermal measurements. This is also not true because emissivity is not related to any color. Different colors placed on the same object will have the same temperature readings. The final myth is that infrared cameras should not be used in daylight. This is also a lie since visible light does not affect infrared cameras in any way. The cameras only respond to infrared radiations and the images taken during the day or nights using the cameras are similar.
Application of Infrared Cameras
Since the discovery of infrared radiation, developments in detector technology has led to the application of the technology in many sectors. The primary users are the police, security agencies, and the military, who use infrared cameras for surveillance purposes (Engert and Merla). This is because the technology can be used to spot intruders even in darkness, or in places such as bushes. Infrared cameras can also detect people hiding behind objects as long as they radiate enough heat to cast a thermal image around the object. This helps keep army and police officers safe from an ambush. The technology can also assist the police to find hidden objects in walls during searches. These objects will act as insulators producing a different thermal image.
Firefighters use thermal imaging to locate people and animals lost in the thick smoke. The device also helps them extinguish forest fires faster by detecting hot spots. Thermal imaging is also used in home performance problems and faults in electrical systems without taking them apart (Meola). Pollution is also monitored using the technology because pollutants radiate different heat from the water and soil around them.
Meteorological departments use infrared satellites to measure ocean temperatures and convection within clouds and get early warnings concerning potentially destructive weather. Geologists use airborne infrared cameras to study rocks, vegetation, soil and mineral distribution. Archeologists use thermal imaging to discover ancient footpaths and roads that provide information about vanished civilizations.
Conclusion
Infrared cameras use infrared radiation discovered by Sir Henry Herschel in 1800 to form visible thermal images that would otherwise not be seen by the human eye. The devices also use the fact that the higher the heat radiation from an object higher the infrared radiation to accurately measure target objects temperature. The price of infrared cameras has limited its use to large corporates, educational institutes, and public service. As a result, most people have not come in contact with infrared cameras causing them to create myths about the device. However, infrared cameras have benefits that have caused it to be used in many sectors for different purposes. The biggest gainers of the technology by far are law enforcement agencies.
Works cited
Engert, Veronika, and Arcangelo Merla. “Exploring the Use of Thermal Infrared Imaging.” PLoS ONE 9.3 (2014): n.pag. Web. 3 Apr. 2016.
Johnson, Steve. “Thermography advantages & disadvantages.” eHow. eHow, 24 Sept. 2015. Web. 3 Apr. 2016.
Kim, Jeonggook, and Junghun Lee. “Appropriate Conditions for Determining the Temperature Difference Ratio via Infrared Camera.” Building Services Engineering Research and Technology (2015): n.pag. Web. 3 Apr. 2016.
Meola, Carosena. “Infrared Thermography in the architectural field.” The Scientific World Journal. Hindawi Publishing, 10 Nov. 2013. Web. 3 Apr. 2016.
National Aeronautics and Space Administration. “Discovery of Infrared Light.” www.nasa.gov. 2012. Web. 3 Apr. 2016.
