Thermal Imaging Module Selection Calculator

Choosing a thermal core is a compromise between field of view, resolution and range. The thermal imaging calculator turns those trade-offs into numbers: enter the detector format, pixel pitch, lens focal length and the target you need to see, and it returns the field of view, the instantaneous field of view (IFOV), the pixels you get on target and the detection, recognition and identification ranges.

What the thermal imaging calculator returns

It works for any uncooled LWIR module — 256×192, 384×288, 640×512 and 1280×1024 — and for the ERUTM and ERUSTM series in particular. Every figure is calculated in your browser; nothing is uploaded.

Thermal imaging module selection calculator

Enter your detector, lens and target. The calculator returns field of view, instantaneous field of view (IFOV), pixels on target and the detection / recognition / identification ranges based on the Johnson criteria.

1 · Detector Resolution (H × V)

Horizontal pixels

Vertical pixels

Pixel pitch (µm)

2 · Lens and target Focal length (mm)

Target critical dimension (m)

Distance to inspect (m) Conditions (practical-range factor)

Detection, recognition and identification range (Johnson criteria)

Ideal range = target size × focal length ÷ (pixel pitch × required pixels on target). Practical range applies the condition factor you selected and is the figure to quote to a customer-facing spec sheet.

What you would see at 500 m

Same lens, different detectors

Comparison keeps the focal length, pixel pitch and target you entered, and varies only the detector format.

How to read the results

Detection (2 px on target) — you can tell something is there.
Recognition (8 px) — you can classify it (person / vehicle / animal).
Identification (16 px) — you can describe it in detail.
Real performance also depends on ΔT, humidity, atmospheric transmission, lens aperture, NETD and the display — always confirm with a field test before quoting a range.

Frequently asked questions

What is IFOV and why does it matter?

IFOV (instantaneous field of view) is the angle each detector pixel sees, in milliradians. It equals the pixel pitch divided by the focal length, so a 12 µm pixel behind a 25 mm lens gives 0.48 mrad. Multiply IFOV by the distance and you get the ground footprint of one pixel, which is what ultimately decides how many pixels a target receives.

What are the Johnson criteria used here?

The thermal imaging calculator uses the classic Johnson criteria: about 2 pixels on the target’s critical dimension for detection, 8 pixels for recognition and 16 pixels for identification. They describe an ideal observer under good contrast — so the tool also shows a practical range that applies a condition factor for haze, rain and low thermal contrast.

Is a longer lens always better?

No. Range grows with focal length, but the field of view shrinks in the same proportion. A 50 mm lens on a 640×512 core sees about 8.8° across — excellent for long-range observation, awkward for searching a wide area. Many UAV and security payloads pair a wide 9–13 mm channel with a narrow 35–50 mm channel for that reason.

How accurate are the ranges?

The figures are geometric and assume the target is fully inside the frame with usable thermal contrast. Real performance also depends on ΔT, atmospheric transmission, NETD, lens aperture, image processing and the display you use. Treat the practical column as a planning figure and confirm critical requirements with a field test.

Thermal Imaging Module Selection Calculator