How Do Thermal Imaging Cameras Work?

How does a thermal imaging camera work

What is a Thermal Imaging Camera?

A thermal imaging camera creates a digital image of an environment by mapping the temperature of whatever is in its view. Every object and surface has a heat signature, created by the energy it transmits, known as infrared energy.

A thermal imaging camera detects the infrared data and converts it into an electronic image with colours indicating temperature variation. It is a non-contact and often handheld temperature-sensing device detecting and displaying object temperature as images.

So, how does a thermal imaging camera work?

How Do Thermal Cameras Work?

To understand how thermal imaging cameras work, disregard everything you know about how photography cameras produce images. They have nothing to do with light bouncing off solid surfaces, in fact, thermal cameras can work in complete darkness.

Heat and light are both parts of the electromagnetic spectrum. However, thermal imaging cameras produce images and video from heat energy, as opposed to visible light. This thermal or ‘infrared’ energy can’t be detected by a regular camera, much like how infrared cameras can’t detect and capture light levels.

The inner workings of a thermographic camera consists of a sensor array that contains thousands of pixels arranged in a grid, which reacts to infrared energy. The focused infrared energy produces an electronic signal to which the camera processor assigns a colour.

Each temperature value has a different colour, which when mapped produces the thermal image of an object or environment.

A Brief History of Thermographic Cameras

In 1800, England-based German astronomer, musician and composer William Herschel discovered the infrared spectrum. Herschel named this discovery the ‘thermometrical spectrum’, occasionally referring to it as ‘the invisible rays”. It wasn’t until the early 1900s that it started being referred to as infrared.

Herschel’s discovery of the infrared spectrum is the basis for modern thermal imaging cameras. It led to many innovations in the field of infrared technology, including the development of the first infrared camera in 1929, a motion camera used by the British army.

Since then, thermal imaging cameras have been used in a variety of fields, including medical, industrial, scientific, and security. They are now widely used in many applications, offering superior performance in dark and low-light conditions.

What Can Thermal Imaging Detect?

Thermal imaging cameras detect infrared heat, which is invisible to the naked eye. All objects give off thermal energy, and the hotter the object the more energy is produced. Think about hovering your hand over a stove to check if it’s been on recently, the heat we can feel in the air is infrared radiation.

Thermal imagers use sensor arrays to detect this heat energy and produce shapes and accurate mappings of heat distribution.

What Can a Thermal Imaging Camera See Through?

All infrared cameras will see the first solid or liquid surface which can include vapour and particles, meaning technically it can’t see through anything. However, it is still sometimes the most effective camera technology for ‘seeing through’ thin plastic, fog, smoke, foliage, dust, fog, rain, sand, snow and darkness.

The displayed images may not be perfect, but in most of these cases, they will produce a clearer image than a visible light camera. For things like search and rescue the image is good enough to detect a person hiding in the undergrowth, but for actual temperature measurement, it’s likely to be inaccurate.

Short wavelength infrared camera optris PI 1M Furnace Application ir-camera-optris-pi-1m-for-metals-industry

What Makes Thermal Imaging Cameras Useful?

Thermal imaging cameras are incredibly useful because they can detect infrared radiation emitted by all objects, regardless of lighting conditions. This makes them highly reliable and efficient, as they can detect heat sources and identify targets in the dark.

Additionally, they are 100% non-invasive, meaning they detect infrared energy emitted from the surface of the subjects without needing any physical contact. They also detect minuscule differences in heat – as small as 0.04°C, and extremely high-tech (and expensive) systems as little as 0.01C.

What are the Limitations of Thermal Imaging Cameras?

Although heat sensing cameras can see shapes and forms undetectable to the human eye, they’re not without their limitations.


Contrary to what you might expect, pointing a thermal imaging camera at a piece of glass at ambient temperature will produce an image of yourself instead of what’s on the other side. This is because glass is highly reflective, stopping the transmission of infrared radiation.

However, at Process Parameters, we can use our cameras very effectively to measure the temperature of glass at high temperatures in manufacturing environments. Using our metal cameras (1M, 08M, and 05M) we can see through ordinary quartz-based glass.


Metal performs in the same way as glass, giving you an image of yourself rather than what you’re trying to capture. Thermal cameras will never be able to see through metal but can detect hot and cold spots on the inside of a metal object or structure.


The water droplets from fog and rain can severely limit the temperature measurement capabilities of thermal cameras due to the scattering of radiation. However, when it comes to producing an image, thermal cameras may still perform better in foggy conditions than the human eye or even a visible light camera.

What is a Thermal Imaging Camera Used For?

Thermal imaging cameras are invaluable for emergency services. From night vision detection during police chases, to search and rescue missions, to firefighters locating survivors in smoke, many incidents could have much more sombre outcomes without thermal camera technology.

In manufacturing, thermal imaging can detect liquid levels in opaque containers, detect hot and cold spots to prevent risk and damage, and improve quality control processes.

For challenging environments, industrial usage may require thermal cameras to meet official regulations for manufacturing standards in the UK. This applies to explosive gases, mining, and applications with high volumes of dust such as grain handling.

Process Parameters’ Thermal Imaging Cameras

All of our infrared cameras are designed for fixed installations and are used to measure temperature accurately. We don’t typically sell into the search and rescue or security industries as the products used to produce images are of a lower required specification than our technology.

We do however sell into industrial applications encompassing research and development, (machine or product developments), condition monitoring (checking equipment is operating properly) and quality control.

We have a variety of cameras. Some for general-purpose applications, some for Glass and others for Metals. Another key customer is those requiring fire detection and prevention, as with our cameras a high temperature can be detected before a fire starts.

Our team here at Process Parameters will be able to assist you with certification requirements for industrial infrared camera usage.

Other uses for thermal cameras include drones, wildlife photography, wildlife tracking, environmental monitoring, airport security, marine traffic monitoring, military applications, building inspections and monitoring patient health.

See Our Thermal Cameras

What to Consider When Choosing a Heat-Sensing Camera

Choosing a particular heat detection product can feel like a complex decision. All the available varieties, price differences, designs, and sensitivities can make it difficult to know what is truly the best option for your application.

  • What is your budget?
  • Do you need to meet any UK, EU or other standards and certifications?
  • Design – aesthetic and ergonomic
  • What are the ideal size and weight?
  • What are your requirements in terms of thermal range, lens interchangeability, hardware and software calibration, image resolution and screen resolution if applicable?

For more information on any thermal imagers, or for further advice, please contact one of our support team who will be happy to assist you.

Send An Enquiry

How do a thermal imaging cameras work

FAQs about How Does a Thermal Imaging Camera Work?

How do thermal cameras measure temperature?

Visible light is the only part of the electromagnetic spectrum we can see, even though infrared radiation takes up a larger percentage. A hotter surface or object produces more heat energy, which thermal imaging cameras can detect. The thermal data is displayed as an image, with different colours correlating with different temperatures.

Is an infrared camera the same as a thermal camera?

Thermal imaging cameras detect heat, which can also be named infrared energy and thermal energy. An infrared camera, therefore, is the same as a thermal camera, as it detects heat and creates an image.

Who would use a thermal imaging camera?

Emergency services are big users of thermal imaging cameras. Fire, search and rescue, police, and generally any work involving finding people and animals in difficult or obscured scenarios. Medical professionals, building maintenance workers, gas and electric workers, and wildlife researchers are also common users of infrared cameras.

How far can a thermal camera detect?

There is no limit on how far a thermal camera can detect, the image will be made up of every visible surface or object within the camera’s range. On a clear night, it’s not unusual for thermal cameras to detect the moon and stars. For example, if there are water droplets (rain or fog) obscuring the vision, then those droplets are the furthest the camera can see.

Do thermal cameras work underwater?

No, they don’t. Water doesn’t transmit the energy required for heat detection. Thermal cameras generally don’t work well underwater, essentially acting as an opaque or solid structure as a barrier to infrared radiation.

Do thermal cameras work through glass?

No. Glass is highly reflective and does not allow thermal radiation to pass through it, stopping the ability of thermal cameras.

Can thermal imaging cameras see through walls?

No, thermal cameras cannot “see” through walls or concrete. However, if there is a hot or cold pipe within the wall, it’s likely a thermal camera will pick up on this.

How does thermal work?

Thermal energy works by transferring heat from a warmer object or system to a cooler one, seeking to reach thermal equilibrium. It follows the principle that heat flows naturally from regions of higher temperature to lower temperature until they become balanced.

How does an infrared camera work?

An infrared camera works by detecting infrared radiation emitted or reflected by objects. It uses an infrared sensor to capture the radiation and then converts it into a visual image, allowing us to see and interpret temperature variations in the scene.

Summary of How Do Thermal Cameras Work?

We hope you found this article on ‘how does a thermal imaging camera work?’ useful. Process Parameters Ltd is the UK distributor for Optris, a manufacturer of infrared thermometers and thermal imaging cameras. Contact our team to discuss your application and find out how thermal imaging can improve your process.

For further information please email or call 01628 778788.

Send An Enquiry

Related Articles:

How Do Infrared Cameras Work?