What Is Infrared? | Teledyne FLIR

What Is Infrared?

Infrared radiation — often referred to simply as infrared or IR — is a type of invisible energy that lies just beyond the red end of the visible light spectrum. Although we cannot see it with the naked eye, we experience it every day as heat. From the warmth of sunlight on our skin to the heat radiating from a machine in operation, infrared energy is all around us.

The Electromagnetic Spectrum and Thermography

All objects emit electromagnetic radiation according to their temperature — a principle defined by Planck’s law. The portion of this radiation that falls between visible light and microwaves, with wavelengths roughly between 0.75 and 15 micrometres (μm), is known as the infrared spectrum.

The human eye detects only a narrow band of electromagnetic radiation (approximately 0.4–0.7 μm). Infrared radiation sits just beyond this range — invisible to our eyes but readily detectable by specialised sensors. The hotter an object becomes, the more infrared energy it emits.

This property allows us to visualise heat, effectively extending human vision into a previously unseen domain.

How Thermal Imaging Makes the Invisible Visible 

Thermal imaging cameras, such as those developed by FLIR, convert infrared radiation into a visible image that represents temperature variations across a surface. Instead of detecting reflected light, a thermal camera measures emitted heat energy — meaning it works equally well in complete darkness, bright sunlight, or challenging weather conditions.

The sensor inside a thermal camera, called a microbolometer, detects changes in infrared radiation and converts them into electrical signals. These signals are then processed into a colourised image where each hue represents a different temperature. This technique, known as infrared thermography, enables the non-contact measurement of surface temperatures with remarkable precision.

Why Infrared Matters in Industry, Safety and Research

Infrared technology bridges the gap between the visible and the invisible, transforming how we monitor, diagnose, and protect. Everything above absolute zero (–273.15 °C) emits infrared energy, so thermal imaging can reveal details that standard cameras cannot — from overheating electrical components to subtle variations in building insulation.

The applications are vast:

• Manufacturing and utilities maintenance – Detect electrical faults or mechanical wear before they lead to costly failures.
• Building diagnostics – Identify heat loss, insulation gaps, and moisture intrusion without invasive inspection.
• Public safety – Empower firefighters, law enforcement, and first responders to locate heat sources and people in low-visibility conditions.
• Scientific research – Measure thermal behaviour in materials, processes, and living systems with high precision.
• Infrared thermography provides not just visibility but quantifiable data, allowing users to assess thermal performance, predict failure, and ensure safety with confidence.

Infrared vs Visible Light — The Key Differences

While visible cameras rely on reflected light, infrared cameras detect emitted energy. This distinction makes thermal imaging uniquely powerful: it does not depend on ambient illumination and is unaffected by shadows or glare. Even “cold” objects, such as ice cubes, emit measurable infrared energy.

In essence, infrared imaging reveals the world as it truly behaves thermally, not as it merely appears optically.

The Science Behind Flir Infrared Cameras

Without MSX (left), with MSX (right)

Flir pioneered modern infrared technology, integrating advanced detector materials, precision optics, and intelligent software into accessible, portable systems. Each camera uses a finely tuned array of sensors that respond to minute temperature differences — sometimes less than 0.04 °C.

Through proprietary image processing techniques such as MSX® (Multi-Spectral Dynamic Imaging) and UltraMax®, Flir cameras merge visual and thermal data to produce detailed, context-rich imagery. This fusion of engineering and science allows users to capture accurate, actionable insights from every thermal frame.

Learn More About FLIR and Infrared Technology

Flir has been at the forefront of infrared innovation for over six decades, advancing the science of thermography from laboratory research to real-world applications across industry, defence, and public safety.

To learn more about how Flir cameras harness infrared to solve practical challenges, explore:

Thermal Imaging Fundamentals Flir Handheld Thermal Cameras Infrared Training Center