Understanding NETD: What Does 25mK Mean in Thermal Imaging?

2026-09-29 10:35:00

What Is NETD?

NETD stands for Noise Equivalent Temperature Difference. It is commonly used to describe the thermal sensitivity of an infrared detector system.

A lower NETD value generally indicates that the system can distinguish smaller temperature differences under specified test conditions. However, NETD should always be evaluated alongside the test conditions and the rest of the optical system.

NETD in Ferolix Products

The Ferolix product range includes several NETD configurations.

The FS Series specifies NETD of ≤40mK at 25°C and F/1.0. The FP68-U, FP7-U and FP8-U specify NETD of ≤25mK. The more advanced FP6C and FP6CL cooled thermal imaging systems specify NETD of ≤15mK.

These different specifications reflect different product architectures and intended performance levels.

Why Lower NETD Can Matter

Thermal imaging depends on detecting differences in infrared radiation. When temperature differences are subtle, thermal sensitivity becomes an important part of the system.

A lower NETD specification can therefore be valuable for applications where users need to distinguish relatively small thermal differences.

However, NETD does not tell the complete story. Lens quality, detector resolution, image processing, environmental conditions and atmospheric effects can all influence practical image performance.

25mK thermal imaging

Several Ferolix products use a 640×512, 12μm thermal detector with NETD ≤25mK.

The FP68-U is one example. It combines thermal imaging with a visible camera, Laser Rangefinder and positioning system.

The FP8-U also specifies 640×512 thermal imaging, 12μm pixel pitch and 25mK NETD, together with low-light and visible channels.

15mK Cooled Thermal Imaging

The FP6C and FP6CL represent a different class of thermal imaging system. Both specify cooled thermal imaging detectors with 640×512 resolution, 15μm pitch and NETD ≤15mK.

These platforms are designed around long-range observation and integrate thermal imaging with visible imaging, laser ranging and positioning.

The FP6CL uses a 15–300mm thermal lens configuration and lists vehicle recognition of at least 12km under the stated product specifications.

Comparing NETD Correctly

When comparing two thermal imaging products, buyers should ask:

1. What is the NETD value?

2. Under what temperature and optical conditions was it measured?

3. What detector resolution is used?

4. What lens is paired with the detector?

5. Is the detector cooled or uncooled?

6. What is the intended observation distance?

This approach produces a more useful technical comparison.

B2B Procurement Considerations

For distributors, NETD can be included in product comparison tables, catalogs and technical specifications. However, marketing materials should avoid presenting NETD as the only indicator of image quality.

A complete specification sheet should include detector type, resolution, pixel pitch, lens, field of view, display, environmental protection and operating temperature.

Conclusion

NETD is an important technical specification in thermal imaging, but it needs context. Ferolix offers thermal systems ranging from ≤40mK uncooled configurations to ≤25mK systems and ≤15mK cooled systems.

Understanding NETD together with detector, lens and system architecture allows B2B buyers to make more technically meaningful product comparisons.