What is a microbolometer?

A thermal imaging device is a tool that allows observation both during the day and at night in any weather conditions. It operates in the thermal spectral range, which is invisible to the human eye, enabling the detection of objects that are inaccessible to night vision devices, regular video cameras, and cameras with infrared illumination.

The key element of any thermal imager is the sensitive sensor. In modern models, this function is performed by a microbolometer, whose quality and characteristics directly determine the device's performance and the quality of the generated image.

What is a Microbolometer

Microbolometer is an uncooled infrared array consisting of a large number of microscopic sensitive elements—pixels. Each pixel reacts to thermal radiation by changing its electrical resistance depending on the temperature of the observed object.

Unlike cooled infrared sensors, microbolometers have several significant advantages:

• do not require cryogenic cooling;
• have compact dimensions;
• consume less energy;
• offer high reliability and long service life.

Thanks to these characteristics, microbolometers are used in most civilian, hunting, and tactical thermal imagers.

How a Microbolometer Works

Thermal imagers operate based on the change in electrical resistance of sensitive elements under the influence of thermal radiation. When heated, the resistance of the element changes, which is detected by the device’s electronic system and converted into a visual image.

Cooled bolometers (used, for example, in astronomy) achieve extremely high accuracy by cooling to liquid helium temperatures. However, microbolometers work without cooling, providing an optimal balance between measurement accuracy, compactness, and energy efficiency.

Modern microbolometers are extremely miniature structures:

• the size of a single pixel can reach 11 micrometers;
• sensitive elements are suspended at a height of approximately 2.5 µm;
• the width of the supporting legs is only 1.5 – 1.8 µm.

The smaller the structural elements of the array, the higher the detail and clarity of the image the thermal imager can produce. Therefore, the further development of thermal imaging technologies increasingly focuses on improving microstructures.

Stages of image formation:

1. The object emits infrared heat.
2. The radiation reaches the microbolometer array.
3. Each pixel heats up and changes resistance.
4. The electronics processes the signal and generates a thermal image.

As a result, the user sees a contrasting picture of temperature differences even in complete darkness.

Microbolometer Sensitivity and NETD Parameter

One of the most common technologies for producing microbolometer arrays is VOx (vanadium oxide). Such arrays feature high sensitivity and low noise levels, providing a higher quality and more informative image.

The key parameter that characterizes a thermal imager’s sensitivity is NETD (Noise Equivalent Temperature Difference) – the noise-equivalent temperature difference. This parameter defines the minimum temperature difference the thermal imager can detect.

Sensitivity is measured in millikelvins (mK):

• up to 20 mK — very high sensitivity (Patriot 2);
• 20–30 mK — professional level;
• 30–50 mK — medium level;
• over 50 mK — basic level.

The lower the NETD value, the more sensitive the infrared sensor and the better the thermal imager can distinguish subtle temperature differences.

Why Sensitivity Matters

High microbolometer sensitivity ensures:

• reliable detection of objects with minimal temperature differences;
• more effective operation in fog, rain, smoke, and high humidity;
• reduced image noise;
• sharper and more detailed target contours;
• increased detection range.

In practice, a thermal imager with a low NETD value can detect a person, animal, or equipment in conditions where a less sensitive device would only show a blurred thermal background.

The microbolometer is rightly considered the "heart" of the thermal imager, and its sensitivity directly affects the device’s efficiency and practical value. When choosing thermal imaging equipment, attention should be paid not only to the array resolution or magnification but primarily to the NETD value. Thanks to the new array with NETD below 18 mK, Patriot 2 from Nvectech produces images with exceptional clarity and detail, allowing users to see the smallest thermal differences, accurately define object contours, and obtain a complete picture even in total darkness or adverse weather conditions.

It is the high sensitivity of the microbolometer that ensures clear, informative images and reliable operation of the thermal imager in real-world conditions.