Thermal Imaging

Thermal Imaging

1. Black body

   • It is a theoretical object that absorbs all of the radiation that falls on it.
   • The peak of emission from a hotter object is at a shorter wavelength(higher frequency) and has a greater intensity.
   • Temperature 300K-object at room temperature. Only infrared radiation is emitted.
   • Temperature 1000K- a red hot object. Emits infrared radiation and red light. The object glows red.
   • Temperature 6000K- a white hot object e.g. the sun. Emits the full spectrum of visible light. The object glows bright white.

2. Cameras

   • False colour
     • detects a range of infrared wavelength.
     • Image produced by this is called a thermogram.
     • Thermograms can show different temperatures using false colour.
     • Allows the operator to easily spot particularly hot or cold regions in the image.
   • Spatial resolution
     • measure of the detal that we can see in an image
     • The greater number of megapixels, the more detailed image.
     • Low spatial resolution- shape loses definiton
     • High spatial resolution- shapes can clearly be distinguished
   • Thermal resolution
     • refers to the ability of the camera to distinguish between different temperatures.
   • Temperature difference
     • can distinguish temperatures in the range -20 to 2000
     • 1.2-1.4 temperatures would appear different in an image, because temperature difference is 0.2, but objects at 1.25 and 1.26 would appear the same, because the temperature difference is much less than 0.2.

3. Advantages

   • Thermal imaging
     • works by detecting different wavelengths of thermal radiation and creates an image showing different temperatures of different objects.
     • It works in complete darkness
     • Can distinguish between objects at different temperatures.
   • Infrared photography
     • uses infrared light with wavelengths just beyond the visible spectrum.
     • normally used on wildlife wouldn't disturbing them. Images look like normal black and white photographs
   • Image intensification
     • visible light is picked up and amplified at very low light levels.
     • Does not require any artificial illumination.
     • Images look similar to normal black and white photographs

4. Uses (application)

   • Inspecting electrical appliances: electrical faults are associated with high currents, which cause greater than normal heating. the cameras can detect these faults at a glance.
   • Firefighting- thermal imaging can show which parts of a fire are hotter than others, heping the fire service to put out a fire.
   • Forensics- if an object has been recently buried, the disturbing ground will be slightly warmer than its surrounding areas. Thermal imaging can be used to find bodies, money or drugs hidden by criminals.
   • Roofing inspection- damp areas of flat roofs may cool down at a different rate to areas that are in a good condition. Thermal imaging can spot these problems before they become serious.
   • Weather forecasting- infrared imaging of clouds, oceans and land masses can provide useful information for predicting the weather.
   • Medical imaging- medical conditions can cause different parts of the body to be hotter or cooler than normal.