LWIR Lenses for Uncooled Thermal Imaging Systems

Longwave infrared (LWIR) lenses form the image on the detector in an uncooled thermal camera. They let your system see through dust, smoke and other obscurants that block visible-light imaging, which makes them a practical choice for equipment that has to work in poor conditions or measure heat rather than reflected light. Wavelength Optics supplies a catalogue range of LWIR lenses from Wavelength Opto-Electronic, with options covering a spread of focal lengths, apertures, mounts and detector formats. Custom designs are available when a catalogue part does not fit your system.

Where LWIR lenses are used

LWIR imaging detects the thermal radiation objects emit. It does not depend on ambient lighting, so it suits applications where visible or near-infrared cameras struggle.

• Food inspection. Thermal imaging on processing and packaging lines can show temperature variation across product, such as uneven cooking, chilling or sealing, without contact and without stopping the line.
• Mass temperature screening. In airports, transit hubs, hospitals and workplaces, LWIR cameras let you screen skin temperature across a flow of people at a distance.
• Vision in fog, rain, snow and haze. For security, perimeter monitoring, transportation and outdoor surveillance, longwave thermal imaging keeps a usable picture in weather that degrades conventional cameras.
• Dusty or smoky environments. Because LWIR passes through dust and smoke, it is useful in industrial monitoring, firefighting and process environments where airborne particulates obscure the scene.

Selecting a lens for your detector

The field of view of an LWIR lens depends mainly on two things: the lens focal length and the size of your detector. A longer focal length on a given detector narrows the field of view and gives more pixels on a distant target. A shorter focal length widens the view for close-range or area coverage. When you compare parts, start from the detector you have chosen and the scene you need to cover, then work back to focal length.

The other parameters to check when you specify a lens:

• F-number. Uncooled detectors are generally less sensitive than cooled ones, so the light-gathering ability of the lens matters. A faster lens (lower F-number) puts more thermal energy on the detector.
• Focus type. Decide whether your application suits a fixed-focus lens or needs adjustable focus for varying object distances.
• Back working distance. Confirm the back working distance is compatible with your camera body, any window or shutter, and the detector package.
• Mount. Match the lens mount to your camera housing to avoid adapters and alignment problems.
• Detector. Each catalogue part is listed against a detector format, so you can shortlist lenses designed for the sensor you are using.

The full specification table on this page lets you filter all of these parameters across the catalogue range.

Custom LWIR optics

If you are building a new thermal camera, integrating a detector into an existing housing, or working with an unusual field-of-view requirement, a catalogue lens may not be the right fit. Wavelength Opto-Electronic offers customization on its LWIR lenses. Send your detector details, target field of view, mechanical constraints and operating conditions through the RFQ form, and the requirement will be reviewed against what can be produced.

Why buy through Wavelength Optics USA

Wavelength Optics is the US arm of Wavelength Opto-Electronic. Working with us gives you a domestic point of contact for the full LWIR lens range:

• Local support. You deal with a US team in your own time zone for questions, orders and follow-up.
• Fast quoting. Send part numbers or an RFQ and we will turn around a quote without you having to coordinate directly with an overseas supplier.
• Technical consultation. If you are unsure which focal length, aperture or mount suits your detector and application, our team can help you narrow the selection before you commit, or define the requirements for a custom design.

Whether you are speccing a thermal camera for a food processing line, a screening station or an all-weather surveillance system, contact Wavelength Optics USA to discuss your LWIR lens requirements.