Infrared Cameras: 3D Vision Explained

Infrared cameras have become increasingly popular in a number of industries, from medicine to security. They work by capturing what the human eye cannot see, using detectors to capture a particular range of invisible energy emissions and then expressing each heat value through a set of corresponding colours. This process is called thermography and the resulting image is a thermogram. Infrared cameras can be used to identify injury and illness, detect deterioration, corrosion, leaks and other potential dangers, and identify security threats. They can also be used to detect the temperature of the human body, which has been invaluable in the fight against COVID-19. But how do infrared cameras see in three dimensions?

Infrared cameras detect invisible wavelengths

Infrared cameras can detect a particular range of invisible energy emissions, typically from 700-1000 nm, and then express each heat value or wavelength through a set of corresponding colours. Warmer areas are usually represented in red, and cooler areas in blue. This creates a thermal image that provides a detailed temperature map of the surveyed area.

Infrared cameras come in three types: short wavelength, mid-wavelength, and long wavelength. Each type detects a different range of infrared wavelengths. Short-wavelength infrared cameras detect wavelengths in the range of 0.9-1.7 microns, very close to the visible light spectrum, and deliver very high resolution. Mid-wavelength cameras detect wavelengths in the range of 2-5 microns and provide higher resolution with accurate readings. Long-wavelength cameras, the most popular type, detect wavelengths in the range of 7-12 microns and provide a great deal of detail due to minimal atmospheric absorption.

Infrared cameras have a wide range of applications. They are commonly used for temperature screenings, building inspections, and medical and veterinary diagnostics. They are also useful for security and surveillance, as they can detect heat signatures and identify people or animals in low-light or dark conditions. In industrial settings, infrared cameras are crucial for preventive maintenance, as they can detect abnormal heat patterns and enhance operational efficiency and safety.

They convert heat into an electronic signal

All objects emit infrared energy, known as a heat signature. An infrared camera, also known as a thermal imager, detects and measures this infrared energy. The camera then converts the infrared data into an electronic signal. This signal is processed to produce a thermal image on a video monitor.

Infrared cameras contain an optical system that focuses infrared energy onto a special detector chip (sensor array). This chip contains thousands of detector pixels arranged in a grid. Each pixel in the sensor array reacts to the infrared energy focused on it and produces an electronic signal. The camera processor takes the signal from each pixel and applies a mathematical calculation to it to create a colour map of the apparent temperature of the object. Each temperature value is assigned a different colour. The resulting matrix of colours is sent to the memory and to the camera's display as a temperature picture (thermal image) of that object.

The final image, or thermography, shows the full temperature of every pixel and not just the average. The colour map, or palette, can be assigned and specifically tailored to give a visual representation of the different wavelength emissions. For example, you may opt to have colder temperatures expressed by the colour blue, medium temperatures by yellow, and hot temperatures by red.

Infrared cameras are used in a wide range of industries. They can be used to identify injury and illness in medical and veterinary settings, detect deterioration, corrosion, leaks, and other potential dangers in electrical and building inspections, and identify security threats or predators in law enforcement or hunting. They are also used in industrial settings as a crucial component of preventive maintenance strategies. By enabling the detection of abnormal heat patterns, such as those caused by overloads or impending equipment failures, infrared cameras can significantly enhance operational efficiency and safety.

This signal is then used to generate an image

The signal produced by an infrared camera is an electronic signal. This signal is then used to generate an image, a visual representation of the scene. The image is created by processing the signal and translating the data into a thermal image or thermogram. This image represents the temperature variations of the objects in the scene.

Each pixel in the image corresponds to a detector pixel in the camera's sensor array, and each detector pixel produces an electronic signal in response to the infrared energy focused on it. The camera processor then takes this signal and applies a mathematical calculation to create a colour map of the apparent temperature of the objects.

The resulting matrix of colours is sent to the camera's memory and display as a temperature picture. This image is a thermograph and provides a detailed temperature map of the surveyed area.

The interpretation of a thermal image is facilitated by a colour palette, where each colour represents a specific range of temperatures. Shades of blue often indicate cooler temperatures, while shades of red signify hotter areas.

Cameras can be cooled or uncooled

Infrared cameras can be cooled or uncooled, and both types have their advantages and disadvantages.

Thermal imaging sensors in cameras "see" the heat radiated by objects and convert it into images. All objects with a temperature above absolute zero emit thermal energy, and this energy increases with temperature. Cooled thermal cameras have a cryocooler that lowers the sensor temperature to cryogenic temperatures. This reduction in sensor temperature is necessary to reduce thermally-induced noise to a level below that of the signal from the scene being imaged. Cooled cameras are incredibly sensitive, but they are also more expensive and less reliable than uncooled cameras due to their complex cooling systems. They are also bulkier and require more maintenance.

Uncooled thermal cameras, on the other hand, operate at ambient temperature. They are compact and well-suited for mobile applications where weight is more important than image quality. Uncooled cameras are much less expensive, making them compatible with compact, affordable devices. They are also more reliable in similar operating conditions and require less maintenance. However, for ranges of 5 km or more, a cooled thermal imaging system may be more economical and better suited to the task as uncooled cameras require costly lenses to increase their range.

The choice between a cooled or uncooled infrared camera depends on the specific application and the level of detail required. Cooled cameras are ideal for applications that require the highest image quality, the ability to see minute temperature differences, fast/high-speed applications, and the ability to measure the thermal profile of very small targets. They are also useful for astronomy, medical applications, and performing spectral filtering to uncover details that would otherwise be unachievable with uncooled cameras. Uncooled cameras are suitable for surveillance, security, building inspections, and mobile applications where weight is a concern.

They are used in many industries

Infrared cameras have a wide range of applications across many industries. They are used in medicine and veterinary medicine to identify injuries and illnesses, and in security and surveillance to detect intruders or threats. In building maintenance, infrared cameras can identify heat losses due to poor insulation or air leaks, and detect water leaks within walls or beneath floors. They can also be used to identify structural defects in construction and engineering.

In industrial settings, infrared cameras are used to monitor equipment and electrical systems, helping to identify potential issues and prevent costly maintenance problems and energy waste. They can also be used to detect gas leaks and electrical problems, ensuring worker safety. Infrared cameras are also useful in manufacturing, for example, in welding, pressure vessel monitoring, glassware manufacturing, and plastic injector moulding.

In the energy sector, infrared cameras are used to monitor critical mechanical and electrical equipment, detect temperature changes, and identify hot spots. They are also used in mining due to their ability to see through smoke and dark conditions and detect the temperature of hot coal. In addition, infrared cameras can be used to monitor the temperature of molten steel and other metals during the production process.

In the automotive and steel manufacturing industries, infrared cameras ensure quality and consistency, and identify energy waste. They can also be used for temperature screening in workplaces, especially during the COVID-19 pandemic, to help prevent the spread of the virus.

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