Why take this lesson?
Getting started with IR products without a solid grasp of the technology is confusing. In this learning path, we aim to teach you the basic infrared terminology and functions. In the end, you can make an informed decision when evaluating and selecting an infrared product for your operational needs.
The entire electromagnetic spectrum and the devices to view it are commonly called “IR” or “infrared”. While “IR” is not wrong, it may not be technically correct. Why? Because there is Near Infrared, Mid Infrared, and Far Infrared.
- Near Infrared: NIR
- Mid-Infrared: SWIR – short wavelengths
- Far Infrared: LWIR or FLIR – long or far wavelengths
- Thermal Infrared: The mid and far infrared energy
- Night Vision Device: A device using near-infrared energy for imaging, commonly called NVGs or NVDs.
- Thermal Device: A device using mid or far infrared energy for imaging
IR’s Beginning: Near, Mid and Far
Years ago, the military released night vision goggles(NVG) to its soldiers. The night vision goggles were sensitive to near-infrared energy so they were often called “IR” goggles. At that time the military’s only focus was near-infrared energy so that worked fine. But over time, thermal devices became a vital part of the operations. And using the term IR device could refer to near-infrared or mid and far infrared. Without more clarification, it was unclear which infrared energy was at work.
What is Near Infrared Energy?
Near-infrared energy (NIR) behaves more like visible red light except that you can’t see it with the naked eye. There are LEDs (your TV remote control) and LASERs that emit near-infrared. Near-infrared is used EXTENSIVELY in fiber optic communications and medical imaging. Most likely, the data for you to read this was sent to you as tiny pulses of near-infrared energy.
What about Mid and Far Infrared?
Mid and far infrared are similar to each other, but very different from near-infrared and visible energy. Neither are visible to the naked eye. The warmth you feel when you stand next to a wood stove or radiator is comprised of mid and far infrared. All objects in the world are continually giving off and receiving mid and far infrared. If I am near a wall, I will radiate energy in the form of mid and far infrared to the wall and the wall will do the same to me. However, if I am warmer than the wall, the amount I transmit to the wall will be more than what the wall transmits to me. Therefore, the wall will cool me off some.
Devices Used to View Infrared Energy
Many devices are used to detect infrared energy. The Military, Law Enforcement, and Sportsmen primarily use Night Vision and Thermal devices. We will focus on those devices in these lessons and how they relate to the NIR, SWIR, and LWIR films that protect and secure their operations.
Night Vision Devices
A night vision device detects and identifies “near-infrared energy,” in the dark. What this means is that objects and people you can’t see in the dark are visible to your eye through the night vision device. The scene will appear in a green color with moderate details. Any existing ambient lights in the scene will bloom larger. The new White Phosphorus near-infrared devices do not have a green tone but appear more black and white for more clarity and definition.