Thermal cameras are commonly used for a variety of purposes in various scenarios. Since the outbreak of COVID-19, businesses are ordering thermal cameras like never before.
But how do they work?
Here’s an in-depth analysis of thermal cameras to tell you all about them. We’ll cover the details of their design, technology, the top brands that deliver the best products, and much more.
A thermal camera is a sophisticated electronic device with an integrated visual display. Now, it may look compact, but there’s a lot going on behind the screen.
The device captures the infrared radiation emitted by an object. It’s then translated into an image through a series of processes. But infrared radiation can’t be seen by the human eye. So a specially designed thermal sensor is used to transform it into visual light.
These images can be used for detailed analysis, report generation, and to make you see better in the dark. These cameras can also be used to measure surface skin temperature. That makes them a popular choice for non-contact temperature measurement.
So what it’s all about?
Let’s get this show on the road.
To begin with, we’ll take a look at their origin story.
It all started in the year 1800. This was when Sir William Herschel discovered the infrared part of the electromagnetic spectrum. Interestingly, the term “infrared” was used much later, in the latter half of the 19th century. Its origin is still unknown.
In 1880, the first bolometer was developed. It’s a device used for measuring infrared radiation. The first thermal imaging devices were designed post World War I. This was for the anti-aircraft defenses in Britain. Subsequently, an infrared line scanner was developed by the US military in 1947. This technology allowed the thermal camera to develop an image.
For a long period, firefighters used these cameras to see through smoke and rescue trapped people. With time, image processing speeds developed and in 1980, the microbolometer was invented. It was developed by Honeywell while working for the US Department of Defense. Finally, the US Government declassified this technology in 1992.
Thermal cameras started gaining popularity by the late 20th century. Most of the modern thermal imaging cameras are based on smart IR sensors. This makes the devices much affordable.
By 2008, the thermal cameras were widely used by home inspectors and contractors. They also became a popular choice for various commercial and industrial applications.
As I have already mentioned, thermal cameras are used for a wide variety of purposes. While a few of the uses are purely for fun, many others have immense practical significance.
Obviously, a major portion of the use is in the defense sector. Beyond that, thermal cameras find application in both industrial and household settings. In addition, consumer-level thermal cameras are also used by hobbyists. Here are a few of the main uses.
Do keep in mind that different thermal cameras have different specifications and limitations. So you need to choose after doing the right amount of research.
Beyond that, thermal cameras are also a favorite tool for casual users. They allow you to explore those normally unseen shades of nature. Besides, you can always capture a cool “thermie” (thermal selfie) with your friends.
Well, it can also make you an absolute champion at hide-and-seek.
Let’s take a detailed look into some of the most important uses of thermal cameras.
Imagine inspecting a large building. Visually, it‘s very difficult to detect air leakages, areas with insufficient insulation, or water leakage. But an inspection with thermal cameras is an easy solution for detecting heating and HVAC problems of buildings.
A thermal camera can easily detect missing or defective insulation and air leaks. It’s also used to detect construction faults and leaks in pipelines. Also, the camera can detect moisture ingress, the location of mold development, and electrical faults.
In many cases, construction issues can lead to the formation of thermal bridges in a building. This can lead to cold areas in a room. A thermal camera can help in locating such areas. Thermal imaging plays an important role in the inspection of new buildings during the construction phase. The technology is also used in the renovation of old buildings.
The other important function is detecting leaked and broken pipelines. Escaping heat from a hot water pipeline is easily detected in a thermogram. Also, thermal cameras can be very effective for scanning electrical installations. They work great for checking fuses and complicated connections.
In the past decades, thermal cameras have immensely aided firefighters. Firefighters use both handheld and helmet-mounted units to see through smoke and dust. They can also detect the amount of energy emitted from a wall or door. This allows the firefighters to proceed carefully through a hazardous area.
A thermal camera is very effective for locating and rescuing a trapped firefighter. They can be used to detect leaking gas and liquid containers. They are also effective to detect overheated electrical equipment and hot spots in the walls. In the case of forest fires, a thermal camera mounted on a drone can help in search and rescue operations.
With the advancement in technology, thermal cameras are becoming more compact and lighter. This is making them more effective for a fire fighting team.
Skin temperature screening is another feature of a thermal imaging camera. By checking every person before they enter a building, those with a fever can be identified. This can help deliver the right level of medical care. Most importantly, this makes these devices a very effective non-contact screening tool.
A modern thermal camera also comes with loads of advanced features. These include enhanced accuracy, speed of detection, and features like crowd detection. However, keep in mind that a thermal camera isn’t a medical diagnostic tool. It can’t detect a virus but is an effective device for screening people.
Keep in mind that thermal cameras are not very effective in measuring a group of people’s temperatures. Also, proper set-up and effective operation are needed for getting accurate results.
For smooth navigation through a terrain, a fully automated driving system needs a lot of data from the external environment. This is a major challenge for engineers working on the development of the Advanced Driver Assistance Systems (ADAS).
For the best levels of safety, the vehicle should be able to see through the darkness, smoke, most fog, and glare. Besides, the performance should not be affected by the glare from light sources like a high sunbeam.
This is where thermal cameras play an important role by detecting infrared radiations from any object. So in a complicated driving environment, these cameras offer great support. They can effectively extend the range of the headlights on a dark night. Many of the top automobile manufacturers offer thermal imaging sensors as a part of the vehicle’s safety equipment.
It has been proven that the use of thermal sensors can improve the efficiency of Automatic Emergency Braking (AEB). The next step is to integrate the thermal sensor data with a range of other sensors and advanced levels of machine learning.
This will ensure smooth performance for fully autonomous driving modes in all weather conditions.
The flexibility of thermography is finding increasing use in the aerospace industry. The main areas of use are quality control, inspection and maintenance, and material testing.
Many companies are using thermal imaging to check elevators located in the aircraft tail. Inspection of fuselages, wings, and rotor blades is conducted by using thermal cameras. This allows inspectors to adhere to high safety standards. To analyze the thermal behavior of aircraft engines, thermal cameras with very high resolutions are used
Besides, the aerospace industry uses various light and composite materials. Various special construction processes are also used. The high-resolution infrared cameras help in the fault analysis of these components. And the best part is, they are non-invasive. This results in a fast and effective fault analysis of the various components.
The visible light that we see occupies a small portion of the electromagnetic spectrum. Infrared radiation occupies a larger part of the spectrum with a wavelength between 700 nanometers (nm) to 1 millimeter.
In case you want to know more about the electromagnetic spectrum, here’s a detailed look:
Note that every object with a temperature above absolute zero emits infrared radiation. But different materials or objects emit hot or cold energy at different rates. This heat energy is captured or detected by the special sensor in a thermal camera. It is then converted into images. This is why a thermal camera can see through darkness, smog, or smoke.
Sounds simple. Right?
But hold on, there’s more.
The amount of radiation a surface radiates has a linear relationship with its temperature. This is what is termed as the heat signature of an object.
To make the image visible for the human eye, the temperature of objects are converted into various shades of gray. In these images, the hotter areas are brighter and the cooler areas are much darker in shade.
Keep in mind that thermal sensors can detect minute temperature variations that can range up to 1/20th of a degree. However, the human eye isn’t capable of detecting such minor variations of grey.
What about RGB coloring?
That’s done too. The camera uses a color filter array (CFA) and specific algorithms to reconstruct a color image.
So, can thermal cameras see in the dark?
You bet they can!
They can detect the heat coming out of objects or living creatures even in absolute darkness. In fact, most cameras deliver an image with sharper contrast during the hours of darkness. This is because the ambient temperature and the core temperatures of various objects are lower during those hours.
Here’s another frequently asked question.
The truth is, thermal cameras don’t see through any object. They just detect the heat signature coming out of the first surface that the camera focuses on. So thermal cameras cannot detect what’s present behind a wall, as most building walls are designed to trap heat.
However, they can detect extreme heat emerging from behind a wall. That may happen when a house is on fire.
That said, a highly sensitive camera can detect the body heat of a person standing behind a thin wall. But only if the body heat can pass through that wall and the sensor is sensitive enough to capture it.
One of the simplest ways to prevent a thermal sensor from working is by putting up a glass wall. Most glasses act as a reflector of infrared wavelengths. This prevents them from reaching the thermal sensor. This is the reason thermal camera lenses aren’t made from glass. However, some glasses, like car windshields, allow more radiation to pass through.
Beyond that, water also acts as a barrier for thermal radiation. So objects immersed in water are very hard to distinguish through a thermal camera.
A thermal camera has three main parts. A lens, a thermal sensor, and a mechanical housing. Beyond that, there are the processing electronics that perform the heavy lifting.
The lens is usually made from materials like germanium, zinc selenide, or Chalcogenide glasses. Now, the lens focuses the captured infrared energy on the sensor. A camera can come with a fixed focus, manual focus, or automatic focus. A sharp focus is essential for clear images and accurate temperature readings.
The focusing is done through the camera optics. The quality of the optics depends on the lens materials and the quality of the coatings used on them.
The sensor comes with a specific resolution which can be between 80 × 60 pixels to 1280 × 1024 pixels. If you compare the resolution to that of the visible light cameras, it is rather low.
Why so? Let me explain.
The reason is, these sensors need to capture larger wavelengths. So the sensor elements are significantly larger. So thermal cameras come with fewer pixels to keep the overall size and ergonomics well-balanced.
Keep in mind that in the case of a thermal camera, the resolution is the key. It will not just determine the image quality, but also the accuracy of the temperature measurement. A high resolution will also allow you to zoom into the image while maintaining good image quality.
The final image is displayed on an LCD screen or monitor that comes with a specific resolution. The camera is encased in a durable casing designed to withstand rugged use. It’s often waterproof and shockproof for use in rough weather conditions.
For a first time buyer, the specifications of a thermal camera can be difficult to understand. The first thing to note is the thermal camera is a digital image converter. It converts infrared radiations into a visible image. So their mode of operation is quite different from a normal digital camera.
So what determines thermal camera image quality?
Basically, three things.
High-quality thermal cameras come with a 640×480 (307,200 pixels). A few top-end cameras also offer 1024х768 resolution levels. Compared to digital camera standards, this seems on the lower end of the scale. However, thermal cameras with higher resolution will be too expensive to manufacture.
Now, a thermal sensor consists of a rectangular array of pixels. The distance between the centers of two adjacent pixels is the pixel pitch or pixel size. For better image resolution, you need a smaller pixel size and higher pixel density.
Basically, pixels capture the thermal data which are then converted into an image. The more the number of pixels, the better is the resolution of the image. It also allows users to target objects from a larger distance without losing the accuracy of temperature readings. The result is a better intuitive diagnosis of problems related to heat.
For example, a 320 x 240 thermal detector can be accurate from a distance of 60 feet. Whereas, a 60 x 120 detector will be equally accurate from a distance of 30 feet.
This is the factor that determines the maximum level of contrast that you can achieve in an image. It also determines the smallest temperature difference the sensor can detect. The value is measured in milliKelvins (mK).
Interestingly, the lower the mK number of a camera, the more sensitive it will be. For most cameras, this value can vary between 250mK to 50mK. A camera with 50mK sensitivity will create the smoothest images that are free from noise. The accuracy levels and the color range of the image will also be better.
The other important factor here is “NETD” or “Noise Equivalent Temperature Difference”. This is a measure of the sensor’s ability to detect very small differences in temperature. A thermal camera with a higher NETD value will show more noise in areas having a lower temperature.
The noise levels depend on the object temperature and also the camera temperature. The aperture of the lens also affects noise levels. In addition, if the ambient temperatures are very high the image can get noisier.
With increased pixel density, non uniformity calibration (NUC) becomes an important factor for a thermal camera.
Actually, how each pixel responds to the infrared energy is different. This is related to the change in the environment and also the internal heat generated by the camera. To get the best image quality, the response needs to be balanced at regular intervals. Or else, the level of noise in the image will go up.
In this process, the camera shutter comes down frequently in front of the detector. The detector uses the shutter as a temperature reference to stabilize the calibrations. This is performed automatically by the camera. The process even takes place for cameras that come with cooled infrared sensors.
Basically, the camera uses this method for stabilization during startup. As the unit warms up and reaches a stable temperature, the process becomes less frequent.
So if you hear a clicking sound while operating a camera, no need to worry. It’s just the algorithmic corrections taking place to ensure the best image quality.
There are two most main types of thermal cameras. These are those with cooled infrared detectors and uncooled infrared detectors.
These cameras are enclosed in a vacuum-sealed case and cooled by cryogenic cooling mechanisms. This is necessary to keep the temperature of the semiconductor materials within operating limits. The operating range for these detectors is within the 60 K to 100 K range (-213 to -173 °C).
While they deliver high sensitivity levels, the process of cooling consumes a significant amount of energy. This also makes them more expensive. So they aren’t suitable for regular purposes and are mostly used for scientific research.
These sensors can operate at ambient temperatures. So they are a popular choice for commercial, and industrial use. These devices are operated by a microbolometer. Since they don’t require any cooling, they are lightweight and easy to maintain.
The most common materials used in microbolometers are amorphous silicon and vanadium oxide. The design allows them to be stored at room temperature for a minimum period of 15 years. However, the camera also needs to deal with its own thermal signature. The point is, the sensitivity levels and image quality is much lower than cooled detectors.
On the other hand, they offer a low-cost solution for thermal imaging. Most handheld and portable cameras come with this type of detector.
Let’s face it. High-end thermal cameras that offer a high level of temperature accuracy come with a high price tag.
Looking for a cheap thermal camera that offers great performance? You’re out of luck.
As you have seen, these cameras come with various components that are expensive. Most visual camera lenses are made from optical glass or plexiglass. But the thermal camera lenses are usually made from Germanium glass. The simple truth is, Germanium is a costly material.
The IR detector is another expensive component that the camera uses. Beyond that, the materials used for converting infrared radiation into electrical voltage signals are also expensive. In addition, a quality algorithm built in the camera is also necessary for proper image clarity. The circuit boards are also designed with extreme precision which makes them costly.
On top of that, you need to add the costs of material transportation, research, and labor costs. The good news is, thermal imaging is becoming more affordable with the advancements in technology.
During the initial days of thermal imaging, a high-quality camera came with a price tag above $50,000. Today, a thermal camera that can be attached to a smartphone can come at a price of around $300. Then again, a top-end thermal camera for precisely measuring skin temperatures can cost close to $5000.
The FLIR TG165 is one of the cheapest thermal cameras that you can pick. It offers a good quality thermal sensor and an easy to use interface for first-time buyers.
There are quite a few brands that manufacture thermal imaging systems for civilian use. Let’s take a look at some of the top brands that have developed a reputation in the market.
Flir is the largest company in the world specializing in the development of thermal imaging cameras. The name Flir is the acronym of the term forward-looking Infrared. Established in 1978, Flir is based in Wilsonville, Oregon, United States.
The brand started with the objective of developing high-performance infrared imaging systems at a low cost. The product range was mostly for airborne applications. In the late 1980s, Flir started to work on hand-held devices to measure temperature differences.
In the late 1990s, Flir acquired Agema (Sweden)and Inframetrics (Boston, MA). In 2003, Flir also acquired Indigo Systems. This gave a major boost to its overall market presence in the field of infrared detectors and cameras. In 2006, it was listed as the 83rd best small business by Forbes.
Flir has constantly worked for cutting down end-user prices while advancing technology. An example of such a product is the FLIR ONE. It’s an advanced thermal camera that can be paired with a smartphone.
The product range from Flir can be used for industrial, home, or outdoor use. Their products are also used for public safety, transportation, marine, and also for security purposes.
The Flir devices offer various advanced features like MSX technology, dynamic detail enhancement, and advanced analytics. From their wide range of products coming at different price points, you can choose the exact features that you require.
Founded in 1948, Fluke has been a major player in the technology market. It caters to various manufacturing and service industries. Its range of products is used in electrical installations, precision measurement, and quality control.
The main highlights of their products are top-notch quality, portability, ruggedness, and ease-of-use. The brand has its manufacturing units located all around the globe, including Asia, the UK, and The Netherlands.
The infrared cameras offered by Fluke meet the toughest industrial standards. They are suited for a wide range of activities including research, science, and engineering development. Its products include handheld infrared cameras and thermal body scanners as well.
The product range from Fluke comes in three different categories depending on the image quality and performance. These are the performance series, the professional series, and the expert series. You’ll find quite a few advanced features in the products. These include Fluke IR-Fusion, LaserSharp AutoFocus, and smooth connectivity through Fluke Connect.
Some of the best devices in their product range are the TiX501 thermal camera and the PTi120 pocket thermal camera. Most of all, the cameras from Fluke deliver excellent reliability and performance.
Seek is a new player in the market of thermal cameras. It was established in 2012 with the goal of making thermal imaging a part of everyday life. Since then, the brand steadily developed top-quality products with excellent imaging capabilities. The headquarters of the company is located in California, USA.
Seek thermal has paired up with brands like Raytheon and NXP to manufacture top-grade thermal sensors. The product range is designed to support industrial needs, firefighting requirements, law enforcement teams, and outdoor activities.
The range of products from Seek are divided into three categories- the Compact series, the Reveal series, and the Seek Shot series. The compact series is designed for smartphones and the Reveal series is for field use. The Seek Shot has advanced features that make it a great choice for professionals.
Some of the popular products from the brand are the Seek CompactXR and the Seek thermal reveal.
Now, Speedir is one brand that isn’t so well known. That’s not surprising considering that they focus on developing thermal cameras for vehicles. They also deliver customer-specific services for automotive use of thermography.
The brand mentions that it has more than 18 years of automotive industry experience. On top of that, there’s a top-notch research and manufacturing facility. It integrates optical, mechanical, and electrical engineering to deliver the best products. They also use AI-based technology to improve overall safety levels.
Imagine driving around in the dark on a foggy night. Not the best time to depend just on your headlights. Right?
This is where Speedir provides HD thermal vision to detect pedestrians and wildlife and help you to drive safely. The high-quality IR sensor captures thermal images 3000ft beyond the range of the headlight beam.
Presently, Speedir has three products in the market for drivers. These are the Night Owl, the Night Owl Plus, and the Prowler Plus.
What if you could your smartphone as a thermal camera?
Sounds great! It really makes the phone more versatile and great for field use.
The point is unless your phone comes with an inbuilt thermal sensor, it can’t generate thermograms. So don’t expect your phone’s visual camera to capture infrared radiations.
And before you ask, an iPhone doesn’t come with a thermal camera. You need to buy a separate accessory like the Flir One that can be connected to the phone. You can also view live thermal imagery on your phone through the Flir One iPhone app.
The camera can also be used for Android devices. You can take a look at our detailed review of the Flir One for more information.
Similar cameras are also available from Seek.
Actually, there are some smartphones that can act as a thermal camera. The CAT S61 Smartphone is one example. It comes with an in-built thermal sensor that can detect a heat source up to 400°C.
Lastly, there are a few free apps for both iOS and Android. These apps can use thermal and night-vision filters to update the images of your smartphone camera. However, they are mostly for fun-seekers. Don’t expect an image quality that’s good enough for professional use.
When you want to share the thermal images or videos or view them live on your smartphone, you need an app. In addition, you can also connect your phone with a hand-held thermal camera with Wi-fi connectivity.
Let’s take a look at some of the best thermal imaging apps for both iOS and Android platforms.
The Flir app works well for devices like the Flir One Pro. The simple interface and the smooth setup makes using it a breeze. Navigating inside the app is very simple and you’ll have no problem.
The app tools allow you to add spot measurements, change color palettes, and adjust the live settings. Beyond that, there are features like thermal panoramas and thermal time-lapse that casual users will dig. You can also share the images with your customers, colleagues, and even on social media.
This app is designed for iOS and Android devices and can work with products like the Seek CompactXR. The app can detect, inspect, and measure the amount of thermal energy being emitted by an object.
The app also allows you to take spot temperatures and inspect the heat source. In our tests, we found the app interface to be simple and smooth in terms of functioning. Navigating between the color palettes and the viewing modes is also easy. On the whole, it provides a smooth experience for professional as well as casual use.
This app is designed to be used with the CEM T-10 thermal imager. We found viewing and storing thermal images and videos is very simple through the interface. The best part is some unique features that it packs.
For example, there’s a point/line/area analysis function for the inspection of objects. You’ll also find a PDF report export function that can be very useful for professional users. You can also use nine different color palettes as per your preference.
Also, you can store images and videos through the app and work on them through a simple interface. You can save or share the modified images as needed.
This app is designed to work with the HT-301 thermal imager. The software allows you to view the thermal images in real-time and also capture videos. While it’s not as smooth as the other apps in this category, it’s a decent option for using an HTi device.
There are plenty of options for temperature measurement. This includes a multi-point temperature measurement, line segment temperature measurement, and frame-selected area temperature measurement.
Keep in mind that Android 10 users need to install the app from the official website. This will ensure a smooth performance without crashing.
Before answering that, let me explain how the two systems differ. A night vision system works by absorbing the available visible light. The system then amplifies this light and present the final images with a greenish hue. Something that we all have seen in the movies.
On the other hand, thermal sensors capture heat signatures and convert them into images.
The problem with night vision is its effectiveness decreases when there’s no ambient light. An overcast night or the presence of fog can affect the performance of a night vision device. At the same time, the resulting images are low in contrast.
Also, night vision isn’t the best choice during twilight hours. During these hours the ambient light might not be enough for the naked eye. But it’s too much for a night vision device to deliver clear images.
As you have already seen, thermal imaging can function even in the absence of any light. It uses thermal energy which is all around us every moment. The infrared sensors can capture the heat signature of objects from a large distance and deliver high contrast images.
Apart from that, thermal cameras can accurately measure temperature differences that make them highly versatile. Do you want thermograms for professional applications or need high contrast vision in total darkness?
Then thermal cameras are the best choice.
However, you may not like the color scheme of thermal cameras and prefer the visuals from a daylight camera. In that case, you can try using a night vision device.
These two cameras work through two different technologies. Infrared cameras operate by generating a beam of infrared energy of a shorter wavelength. This device is called an infrared flashlight.
The generated infrared beam illuminates the target and some of it is reflected back. The camera captures this reflected light and amplifies it with the help of the ambient light to generate an image. Basically, it’s an image intensification device.
On the other hand, the thermal camera detects mid or long-wavelength infrared radiations from the emitted heat from an object. They measure the differences in the heat signature between various surfaces and present the output in an image.
Note that they don’t make use of reflected light. So the image quality remains unaffected by the presence of other light sources or environmental factors. These include headlights, smoke, haze, dust, etc.
So, infrared cameras will have the same limitations as night vision devices. These include a small range and images with lower contrast. They are also affected by extreme weather conditions. Besides, they aren’t the best choice for detecting objects in shadows.
How much resolution you need depends on two factors- your application and the image quality needed. Let’s take a look at the basic resolution standards available in the market for thermal cameras.
Low resolution- 160×120 (19,600 pixels)
Medium resolution- 320×240 (76,800 pixels)
High Resolution – 640×480 (307,200 pixels)
We have already discussed the details about the pixel arrangements in the previous sections.
So an image with low resolution will have one-fourth of less information than the one taken at medium resolution. With higher resolution, you get better picture quality even from large distances. It also allows you to zoom into the image without sacrificing image quality.
But that’s not all.
In the case of thermal cameras, the resolution also affects the temperature measurement accuracy.
To sum up, a thermal camera with better pixel resolution will offer the following advantages.
We suggest that it’s always best to pick the highest pixel resolution that your budget allows.
On the contrary, thermal cameras can help you to walk away from potentially dangerous situations. Firstly, there are no health risks associated with thermal cameras. Thermography is a non-invasive procedure when used for healthcare.
Apart from that, thermal cameras can be very useful for home security. They can also be effective for nighttime adventures. Temperature measurement is also a useful tool for preventive inspection in critical facilities.
Quite simply, it’s one of the best tools that you can use for evaluation, diagnosis, or just for some fun.