Why Thermal Camera Sensitivity (NETD) Matters for Accurate Detection

Selecting the Right Thermal Camera: Understanding Thermal Sensitivity (NETD)

As thermal cameras become more widely used and thermal detection systems more advanced, the design and integration of thermal imaging systems needs to be more commonly understood. With more camera manufacturers entering the thermal space, it's essential to understand what distinguishes a basic thermal camera from a high-performance model.

With visible light cameras the most influential performance specification is resolution. Resolution defines how sharp a visible image is. However with thermal cameras, imaging performance and quality depends far more heavily on a key metric called NETD (Noise Equivalent Temperature Difference). The NETD specification defines how small the temperature variations are that the camera can detect, which directly impacts thermal image quality and analytics performance.

What Is Thermal Sensitivity (NETD)?

NETD is another way of saying Thermal Sensitivity. NETD, or Noise Equivalent Temperature Difference, represents the smallest temperature difference a thermal camera can detect, measured in milliKelvin (mK). A camera with a lower NETD specification means it can detect finer temperature shifts, leading to clearer thermal images.

In simple terms, the lower the NETD, the less noise there is in the image and the sharper the thermal detail. Higher NETD values make images grainier and can reduce the camera’s detection performance, especially if outdoors in difficult conditions like rain or fog.

While other factors like optics F-stop and thermal sensor resolution also play a role in image quality, NETD is the most significant, whether measuring absolute temperature or looking for temperature contrasts to segment an image.

How does NETD Affect Image Quality? Thermal cameras render images based on temperature differences, assigning shades of grey to temperature levels. A low NETD allows the sensor to detect more temperature levels and so more nuanced variations, resulting in a smoother and higher contrast image with more detail. Here’s a basic quality scale: • <25mK – Excellent • <40mK – Great • <50mK – Good • <60mK – Acceptable • <80mK – Basic Lower NETD enhances detection accuracy and reduces false alarms when used with analytics software. It also provides better visibility in poor weather for surveillance applications.

Both images: Figure 1 and Figure 2 are captured with the ambient temperature at ~12.80 C and while raining. The camera used for Figure 2 has a NETD of <35 mK and so provides a much crisper image with sharper scene details and much higher contrast.

Resolution vs NETD

Many thermal cameras offer 640×480 resolution,and pricing can vary widely between models with the same resolution. Often, the difference lies in NETD. Two 640×480 pixel cameras can have identical pixel counts, but the camera with the lower NETD will produce a higher quality image. Higher resolution cameras with poor NETD may very well under perform when compared to a lower resolution better NETD camera when it comes to image clarity and detection range.

How does Thermal Sensitivity (NETD) Enhance System Performance?

OEM thermal cameras are most widely chosen for automated thermal solutions and stream thermal images in real-time time on interfaces like USB, GigE and MIPI CSI-2. In these cases thermal image processing is done by edge processors or by centralised computing hardware. Either way automation, analytics and AI software benefit greatly by the quality of images they are being fed. NETD plays a crucial role in how well these systems perform. As with visible cameras, thermal camera systems perform better and more reliably with sharper, high contrast and detailed images.

Key Takeaways

If you’re investing in thermal technology, don’t compromise. Thermal cameras excel where visible ones fail, through darkness, rain, fog, and snow. But without strong NETD performance, much of that advantage is lost.

Prioritise thermal sensitivity to ensure better accuracy, higher-quality imaging, more reliable object detection, temperature measurement and long-term value, whatever the conditions.

Ask Adept Turnkey for Help
Choosing the right thermal camera involves more than just resolution. Understanding specifications like NETD and how they impact your system's performance can be critical to achieving accurate results. Our Vision Engineers at Adept Turnkey are experienced in evaluating thermal imaging requirements and helping customers select the best camera for their application. Please get in touch, if you need advice or help with thermal camera selection or integration.