Understanding Thermal Camera Limitations

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Last updated on May 11, 2021

Anomalies in temperature can be indicative of risk or danger in certain situations. That’s why it’s important to equip yourself with the right technology that allows you to detect even the most subtle temperature differences when the circumstances call for it. Thermal cameras can pick up anomalies and provide you with an image for you to see what you’re dealing with. While thermal cameras have their advantages, there are also limitations and disadvantages that can make thermal cameras tricky to operate.

Thermal cameras, also known as thermal imaging devices or systems, are used in a wide variety of industries. In this article, we’ll be discussing how thermal imaging cameras work, the technology behind them, and how to use such equipment. We’ll also cover what they are commonly used for, how they can produce an image, and what limitations and disadvantages they may have in temperature measurement to provide you with a better idea of what you will be working with.

What are thermal imaging cameras?

According to the Department of Homeland Security, thermal cameras are non-contact devices that pick up and analyze body temperature or infrared energy before turning it into a visual image. When thermal imaging cameras are used correctly, they can measure surface temperatures without needing to be physically close to the subject.

Alongside Non-contact Infrared Thermometers, thermal imaging cameras are used to measure object or body temperature. Each type of device utilizes a different type of infrared technology to analyze and pick up temperatures. Like standard thermometers, thermal imaging cameras have been on the market for a long time and are readily available.

Where thermal camera technologies are used

thermal imaging technology

Various professionals across different industries utilize thermal cameras in different systems around the world. One of their biggest advantages is they are low in cost while being easily obtainable.

One of their main advantages is that they can detect temperature anomalies without the need for close contact. For example, businesses use thermal cameras to do initial temperature checks on their employees before they enter the building.

Aside from being a useful tool for businesses, thermal cameras can also be used to produces images for surveillance and military purposes, home inspections, electrical inspections and research and development. Firefighters also utilize thermal cameras to assess a site during a crisis response.

How thermal imaging technology works

Thermal imaging cameras do not work the same way regular cameras do. Instead of creating images from visible light, thermal cameras make images from infrared or thermal radiation. A regular camera works similarly to how the human eye detects and perceives images. Light hits a body or an object, bounces off it to create a reflection, then the detector produces an image.

Although both heat and light are both a part of the electromagnetic spectrum, regular cameras aren’t equipped with the ability to produce pictures from thermal energy. In the same way, thermal imaging systems can’t make images using visible light. Thermal imaging technologies rely only on thermal radiation or heat to produce data.

Infrared Radiation

How thermal cameras work

Thermal imaging cameras consist of four parts: a thermal sensor, processing electronics, a mechanical housing, and a lens. The camera's resolution depends on the pixel configuration of the sensor, which can range from 32 x 32 pixels to 1280 x 1024 pixels. The lens takes in infrared energy and focuses it on the thermal sensor to conduct temperature measurements.

The resolutions of thermal cameras are lower than imagers that rely on visible light. This is because thermal imaging systems need to pick up on energy that travels on much larger wavelengths than visible light does. This means that their sensors have to be larger, translating to fewer pixels than those of visible light sensors. A thermal camera then measures infrared radiation using microbolometers which assign a pixel to a corresponding color.

how do thermal cameras work

With different types of thermal imaging cameras, it’s important to analyze the specifications of each one to choose the right camera for you. Different use cases have different requirements.

Take a look at the thermal camera's resolution, the field of view, range, focus, spectral range, and thermal sensitivity to get a clearer view of all the features it can offer you.

It is important to note that almost everything radiates thermal energy. Even cold objects, like ice, give off thermal energy. The general rule is that the higher the body temperature of a person or an object is, the more thermal energy it emits. The emitted thermal energy or surface temperature is known as the subject's "heat signature", which is what analysts study and observe.

A subject’s heat signature can be detected regardless of lighting conditions. Subtle differences in temperature or radiation can be picked up by thermal imaging sensors, then reflect in the images created by the thermal camera. This means thermal imaging cameras can see in near-total darkness or haze-filled environments.

The limitations of thermal imaging systems

Thermal imaging systems are incredibly effective tools for various industries in detecting anomalies in temperature. However, these devices will only function efficiently in certain conditions. Here are some of the limitations and disadvantages of thermal imaging devices.

Glass and other materials

Thermal imaging devices cannot see through or penetrate glass, which is perhaps one of its main disadvantages. Glass acts as a mirror for thermal imaging devices—they won’t be able to produce an accurate image of bodies or objects on the other side of the material. Additionally, thermal imaging devices can’t pass through most walls due to thickness and insulation. A thermal imager would be able to pick up the heat radiated by the wall itself, but it will not be able to detect the temperature of whatever is on the other side of the wall.

glass

Underwater use

Thermal cameras typically do not function well underwater. Similar to how thermal cameras cannot see through glass, water tends to block off most infrared wavelengths, making it difficult for the thermal camera to produce a clear image.

underwater

Detection but not identification

A thermal camera can detect temperature anomalies or inflammations in the body, but it cannot fully identify symptoms. They cannot provide health care professionals with all the data they need, and relying solely on a thermal imager isn’t likely to provide a person with accurate health information.

Thermal camera resolution in some cases isn't high enough to identify a subject, it can only detect that there is a subject.

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Fever detection

You are likely to see thermal imaging systems at any health care facility you visit. Because thermal imaging technology can detect abnormalities in temperature, it can indicate if a person has a fever. For example, in the emergency room of a hospital, a thermal imaging system may assist in measuring a patient’s temperature and help determine who requires isolation or further evaluation.

However, although thermal cameras do detect high temperatures, a health care professional will still need to conduct further tests to discover the root cause of the elevated temperature and what steps should be taken next.

Accuracy

While temperature scanning systems may detect fevers, they aren’t completely accurate. These cameras can be set up in areas with high foot traffic to get the initial temperature readings of a person, but they aren’t effective in screening people's temperatures in bulk.

It is important to note that these systems tend to have lower temperature readings than those measured by an oral thermometer, so adjustments need to be made accordingly to make up for temperature differences. Each thermal camera also works differently according to its specifications, so the images each one produces will vary.

Daytime use (thermal noise)

In most scenarios, thermal cameras can be used during the day. However, the amount of sunlight present may mess with the images produced by your thermal camera because of the heat that it may potentially get added to the subject. Light may also generate a lot of noise in your image, making it harder to study.

How to block infrared cameras

Thermal cameras will not be able to produce an accurate image through glass or water, but other materials can be used to block infrared cameras. Generally, materials with high electric conductivity will block off infrared radiation. Acrylics and some polycarbonate materials can also block off infrared cameras.

Randy Angwin

About the author

Randy Angwin is an avid outdoor enthusiast and has been with Smart Scouter since the beginning. He helps create new articles and reviews latest infrared and night vision devices for the site as well as staying on top of the latest trends in the thermal industry. When not working, Randy likes to hunt and spend time with his two German shepherds.

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