How pixel pitch affects thermal imaging quality: A guide to choosing the best thermalimager

When selecting the ideal thermal imager for your needs, understanding the impact of pixel pitch is critical. Pixel pitch directly affects image quality, base magnification and sensitivity - key factors that determine the overall performance of a thermal imager. Now, we'll break down the technical aspects of pixel pitch and offer practical tips to help you make your decision.

What is pixel pitch and why is it important?

Pixel pitch refers to the distance between the centres of adjacent pixels on a thermal imaging sensor. Typically measured in microns (μm), smaller pixel pitches (e.g. 12 μm) allow for higher resolution in a more compact sensor. Larger pixel pitches (e.g. 17 μm), on the other hand, can capture more infrared radiation per pixel, resulting in higher sensitivity.

Key takeaway: The choice between a 12 μm and a 17 μm sensor involves balancing compactness, resolution and sensitivity, depending on the intended application.

Resolution and sensitivity: A balancing act

Thermal resolution

Thermal resolution, often defined in terms of Noise Equivalent Temperature Difference (NETD), measures a sensor's ability to detect small temperature differences. A lower NETD (e.g. <25 mK) indicates higher sensitivity, which is particularly beneficial in low-contrast scenes where objects and their backgrounds have similar temperatures.

Tip: Choose a low NETD if your primary application involves detecting subtle temperature changes, such as search and rescue or night wildlife observation.

Spatial resolution

Spatial resolution defines a thermal imager's ability to distinguish between closely spaced objects. While a smaller pixel pitch generally improves spatial resolution, it's important to note that devices with artificially enhanced NETD values through image filtering may compromise true spatial resolution.

Tip: Evaluate the sensor's native resolution and NETD before purchasing, and be wary of exaggerated claims in marketing materials.

Advantages of smaller pixel pitch (12 µm)

1.Compact design: Smaller pixels allow for smaller sensors, resulting in lighter and more portable devices.

2.Wider field of view: For the same resolution, devices with smaller pixel pitches can use shorter focal length lenses, providing a wider field of view for tracking fast-moving targets.

Trade-off: Smaller pixel pitches may have slightly higher NETD values than larger ones, meaning that sensitivity may be reduced in certain scenarios.

Advantages of larger pixel pitch (17µm)

1.Higher sensitivity: Larger pixels capture more long wavelength infrared (LWIR) radiation, resulting in lower NETD values and better performance when detecting low contrast targets.

2.Improved detail in low contrast scenes: Devices with 17 μm sensors excel in scenarios such as thermal inspections or game spotting in dense environments.

Practical tips for choosing the right thermal imager

Understand your application needs:

1.For outdoor adventure or hunting, prioritise compactness and resolution (12 μm).

2.For professional inspections or law enforcement, prioritise sensitivity (17 μm).