Night Vision: Active Infrared vs. Thermal Infrared

Daylight TV cameras, image intensified (I²) night vision devices, and the human eye all see the same thing: reflected visible light.

Unfortunately, we need visual contrast to discern an object from its surroundings and at night there is very little visual contrast to work with. Conventional night vision scopes are great for situational awareness, but they can\’t see in total darkness. Conventional night vision scopes also struggle to penetrate foliage or make a picture at great distances.

The examples below demonstrate how Image
Intensified Night Vision and Thermal Night vision differ.

Active Infrared


Thermal Infrared


Visible Light Camera / Human Vision


Thermal Infrared


Thermal Energy in Day-to-Day Life

Everything we encounter in day-to-day life gives off thermal energy, even ice. The hotter something is, the more thermal energy it emits. This emitted thermal energy is called a heat signature. When two objects next to one another have even subtly different heat signatures, they show up clearly to a thermal imager regardless of lighting conditions.


Thermal imaging cameras will vary in price depending on the features of the camera. The camera\’s resolution and lens options will often dictate the price. The higher the camera\’s resolution, the better image clarity and detail you will see on images and video.


Binocular vs. Bi-Ocular; know your devices

Seeing the Difference: Binocular vs. Bi-Ocular Thermal Night Vision Cameras


For many people the difference in the words binocular and bi-ocular are not apparent or clear at first. Binocular sights consist of two eye piece channels that deliver a slightly different image to each eye. In return the brain compiles the two images to create one image. When paired with night vision technology this information is relayed to the viewer via two optical channels while amplifying light to display an image.

Bi-Ocular Differences


A bi-ocular night vision thermal imaging camera is composed of two separate eye pieces, but only one optical channel, thus delivering one image to both eyes at the same time.  A bi-ocular thermal camera detects infrared light, which is given off by the heat of an object in view, the microbolometer lens detects heat and displays the thermal image to the viewer.

Benefits of the Bi-Ocular

The benefit of using a FLIR H-Series Bi-Ocular thermal night vision camera during patrol, covert surveillance, or security mission is the extreme sensitivity and low temperature readout. The presence of a suspect or vehicle with a recent source of heat is clearly seen through fog, low light situations, and tree cover.
Available models include the FLIR BHS-X Command and the FLIR BHS- XR Command. Additional FLIR accessories are also available to enhance your detection range.