Thermal imaging is detection of heat that an object emits. By measuring what the body emits, we can make a picture of the temperature of the body. What we’re looking for, in a thermagram is differences. We can take that information and build conclusions.
Thermographers use this heat detection device (THERMAL CAMERA) for infrared imaging, which looks like a regular camera. It’s used to scan the to determine variations in heat patterns on the body. The image it takes can be displayed on a monitor, or computer screen, for analysis.
Thermography ( IRT) , is especially useful in identifying fluctuations in blood flow, which can indicate problems in soft tissues. The blood flow can vary, depending on whether circulation is normal or affected by injury. IRT can be an early indicator of a problem because blood flow to an injured area may increase before clinical signs of pain and lameness become evident, sometimes early as 2 weeks in advance!
To fully understand how a thermal image, or thermogram is produced, some background knowledge of the physics of light is needed. Light is emitted in waves. The amount of energy in each light wave is related to its wavelength; shorter wavelengths have more energy. Visible light is made up of a spectrum of colours (those you seen in a rainbow), in this spectrum violet has the most energy and red has the least. As well as the visible light spectrum there are also UltraViolet (UV) and InfraRed (IR) Spectrums either side of it. These can't be seen with the naked eye.
The IR Spectrum is the part of light that we're interested in when capturing IR images. Infrared light can be split into three categories; 1. Near IR; closest to visible light, near infrared has wavelengths ranging from 0.7 to 1.3 microns (or 700 to 1300 billionths of a metre); 2. Mid-IR; has wavelengths ranging from 1.3 to 3 microns; 3. Thermal-IR; has wavelengths ranging from 3 to 30 microns. You're probably very familiar with both near and mid-InfraRed as they're used by a variety of electronic devices, e.g. remote controls.
Thermal IR makes up the largest part of the IR Spectrum and is also known as heat. Thermal-IR is the part of the Spectrum we're interested in for Thermal Imaging. The key difference between Thermal-IR and the other categories is that it's emitted by an object instead of being reflected off it. Animals emit IR radiation as a result of normal physiological processes.
An IR camera is used to measure the heat photons emitted from the animal or human and to convert them into electrical impulses which are then displayed as colored images on a monitor. This visual image graphically maps the animal’s body temperature and is referred to as a thermogram. The heat detector, or microbolometer within the thermal camera can detect differences in temperature of less than 0.05oC, which is 40 times more sensitive than the human hand.
Thermal imaging cameras have the ability to simultaneously take and then fuse together visible light and thermal images.