Thermal Vision

See in the dark


Thermal Vision

Table of Contents

Thermal Vision is a optoelectrical device containing a compact thermographic camera, and can be used in a variety of manners from goggles and binoculars to rifle scopes. Capturing and analyzing the data the cameras provide is called thermography, which uses the non visible light spectrum called infrared.


Thermal vision devices can operate in total darkness, and can be quite useful in places with cold nights as the extreme difference in temperatures between the cold ground and any source of heat (such as a feral pig) creates a high visual contrast between the two. This makes it easy to locate any source of heat against its low-temperature background.

Thermal has an added bonus feature of ignoring light scrub and foliage as well as ignoring dust, mist and fog.

Light wavelength units of measurement

  • 1 micron (µm) = 1 micrometer = one millionth of a metre (m)= one thousandth of a millimeter (mm)
  • 1 nanometer (nm) = one thousandth of a micron (μm) = one billionth of a meter (m)
  • 1 Ångström (Å) = 10 nanometer (nm) =10 billionths of a meter (m)

Visible Light

Humans can see visible light in the range of 400 nanometer (nm) or 0.4 micron (μm) “Violet” to 700 nanometer (nm) or 0.7 micron (μm) “Dark Red”.

Spectrum of Visible Light
Spectrum of Visible Light

Infrared Light

We, as humans, can detect infrared waves as heat but we cannot see them.

The region that the infrared spectrum operates is in wavelengths from 0.78 to over 1000 microns (µm). This region is divided in to classes.

Table of Infrared Light Categories
Name Range start in microns (µm) Range end in microns (µm)
Near infrared 0.78 1.4
Short wavelength infrared 1.4 3
Mid wavelength infrared 3 8
Long wavelength infrared 8 15
Far infrared 15 > 1000

Near infrared is called “near” because it is closest to the visible light spectrum.

Infrared wavelength spectrum
Infrared wavelength spectrum

The remote control on a TV operates just inside this invisible part of the spectrum to allow us change channels with infrared waves of light.

Thermal Vision

Thermal vision is facilitated by a camera, known variously as a:

  • thermographic camera
  • infrared camera
  • thermal imaging camera
  • thermal camera
  • thermal imager

These devices create an image using light waves in the infrared part of the light spectrum.

Infrared cameras are sensitive to wavelengths from about 1,000 nm or 1 micron (μm) to about 14,000 nm or 14 micron (μm). This covers the thermal part of the infrared spectrum, which has wavelengths ranging from 3 micron (μm) to over 30 micron (μm).


Thermal Vision Device Operational Process
  1. The thermal infrared image is delivered through the objective lens of the thermal imaging device.
  2. A phased array of detector elements create a pattern called a temperature difference map or thermogram in high definition. 
  3. The thermogram is changed into electrical impulses.
  4. The impulses are processed by a computer chip and made into data. 
  5. The resulting data is displayed on a screen in the form of a visible image.
thermal imaging display
Thermal imaging display

Most thermal-imaging devices scan at a rate of 30 times per second.

Thermal Vision Device Enhancements

Because a thermal vision device is basically digital, this allows for a raft of enhancements made possible by the onboard microchip. These can include:

  • Brightness and contrast controls
  • Image color settings
  • Display enhancements like the time, battery charge level, notifications
  • Digital zoom 
  • Picture in picture
  • The ability to turn the display off ( Saves battery)
  • Reticle selection
  • Wind adjustment
  • One shot zeroing 
  • Freeze zeroing
  • Distance correction
  • Side tilt indication
  • Elevation angle
  • Altitude
  • Multiple rifle profiles
  • Ballistic calculator
  • Shot recorder

Connectivity via radio, wifi and bluetooth giving access to laser rangefinders, GPS and data transmission and reception. Have a look at the ThOR 4 from ATN:

Thermal Vision Temperature Range

Most devices can detect temperatures ranging from -20 degrees Celsius (-4 degrees Fahrenheit) to 2,000 degrees Celsius (3,600 degrees Fahrenheit), and can normally detect temperature changes of approximately 0.2 degrees Celsius (0.4 degrees Fahrenheit).


The beginnings of heat differentiation or thermography is known to have dated back at 4,500 years ago with the recognition of heat and its association with human disease.

In whatever part of the body excess of heat or cold is felt, the disease is there to be discovered.


Below the red

Royal Astronomer to King George III, Sir William Hershel, was experimenting with prisms to separate the various colors of the rainbow. He discovered an invisible spectrum of light. Infrared, which mean “below the red.”



The first camera

The first camera sensitive to infrared was invented by a Hungarian physicist named Kalman Tihanyi.



Camera taking still images

A camera was invented that would take still images, but took an hour to produce just one photo.



1st Thermal imager used fighting fires

Phillips and English Electric Valve develop the first naval thermal imager used by the Royal Navy for firefighting.




Microbolometer technology developed.


Thermal Vision Pros and Cons vs. Night Vision


Summary: Thermal vision devices are pricier than night vision as well as heavier. They do come with a raft of benefits however. The ability to be used in all light conditions and be able to see through scrub and airborne particles to name a few.

Australian Rules and Regulations

Thermal Vision Devices are legal in Australia. However states have their own regulations on their use. New South Wales does not allow the use of thermal vision when hunting in their state forests and Victoria classifies thermal vision devices as spotlights and there are hunting restrictions applicable.

Thermal Vision Devices

Hunters have been quick to take up with thermal vision devices have as prices have come down. The technology can offer tremendous benefits to a wide variety of applications.

Thermal Vision Binoculars

Pulsar MERGER LRF XL50 Thermal Imaging Binoculars
Pulsar MERGER LRF XL50 Thermal Imaging Binoculars

Thermal Vision Scopes

Pulsar Thermion 2 Pro thermal vision rifle scope
Pulsar Thermion 2 Pro thermal vision rifle scope

FAQ (Frequently Asked Questions)

Thermal scopes operate with an infrared camera which detects heat from the thermal part of the infrared spectrum. Heat is emitted from an object at the atomic level. This is processed and delivered to the viewer in visible light.

Thermal vision devices are legal in Australia. However states have their own regulations on their use. Some states do not allow the use of thermal vision devices when hunting on certain public lands and some put thermal vision devices in the same class as spotlights and are likewise restricted for same circumstances.

According to the Australian Customs and Border Protection Service, it is illegal to import thermal vision devices without a permit. Permits may be granted for the import of thermal vision devices for certain purposes, such as scientific research, education, and testing.

Yes, as the thermal vision camera detects emitted heat then it can function in complete darkness. An advantage over night vision devices (NVD’s).

The distance at which you can see with thermal vision can vary depending on a number of things, such as the type of device, the temperature differentiation between the background and target, and the size and heat signature of the target. Thermal vision does not have the resolution of a normal daytime optic.  ATN quote a visual range on some of their devices at 3,000 yards but the identification range is a good deal less.

Photo Credits: Pulsar, ATN

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