Teledyne FLIR Lepton 3.5

The Teledyne FLIR Lepton 3.5 is a miniaturised radiometric thermal core from the USA for small platforms, including the small FPV class. It sits, for example, in the Flyability Elios 3 inspection aircraft and is built into devices as a component rather than sold as a finished camera.

The detector is an uncooled microbolometer for long-wave infrared with 160 × 120 pixels at a 12 µm pixel pitch. The module is radiometric, so each pixel carries a temperature value. An integrated shutter calibrates the image periodically; the field of view is 57°. The frame rate is 8.6 Hz. It is kept low so that the module stays exportable, and it suffices for inspection, but the picture looks jerky during fast movement. As a miniaturised core, the module fits into very small aircraft.

At 8.6 Hz, the frame rate stays below the 9 Hz limit above which thermal modules fall under the EU Dual-Use Regulation; the core is therefore easier to handle for export. The manufacturer lists it as ITAR-free and NDAA-compliant. Images of people and property fall under data-protection law, and the operator must be registered.

With 160 × 120 pixels, the module recognises only coarse heat patterns; for fine detail or measurements from a distance, 320 × 240 or 640 × 512 are better suited. As a core, optics, housing and image processing are part of the integrator's design. Points to check are the shutter, the connector and contamination on the front lens.