LWIR cameras are the powerhouse behind thermal imaging

Thermal imaging of objects at or near room temperature is typically done in the 8–14 μm longwave-infrared (LWIR) spectral band, as the Planck curve for blackbody radiation for room-temperature (300 K) objects peaks in the LWIR at about 9 μm. LWIR imaging has the great advantages of being able to image objects by their own light and discriminate between objects based on their temperature; in addition, LWIR imaging works well for outdoor use due to the relatively low output power of the Sun at LWIR wavelengths.

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The most widely used sensor type used in LWIR imaging, and the one most covered in this article, is the uncooled bolometer focal-plane array (FPA), which is usually (but not always) based on vanadium oxide. The list of applications for LWIR imaging is extensive, and includes many uses in surveillance and security; biology, geology, and other sciences; industrial inspection and process control; and medical and veterinary fields. This article provides a bit of background on some commercial examples of current LWIR imagers.

Small-pixel imagers

Leonardo DRS (Arlington, VA), which produces uncooled vanadium oxide microbolometer FPAs, camera modules, and camera systems for military and commercial markets, has developed a line of small-pixel (10 μm pitch) arrays to complement its line of 17-μm-pitch arrays, as described by Doug Ransom, VP of Leonardo DRS’ Electro-Optical and Infrared Systems business. Its 1-μm-pitch arrays, including the U (640 × 512) and the U ( × ) FPAs, are the sensors for the company’s Tenum 640 and Tenum camera modules as well as for cameras used in several U.S. military programs. DRS’s 17-μm-pitch arrays, including the U (320 × 240), U (640 × 480), and U ( × 768) FPAs, are the sensors in the company’s Tamarisk family of camera modules as well as various other DRS system-level products.

“The most recent DRS advances in pixel design and process improvements allow reductions in pixel size while still achieving desired performance levels,” says Ransom. “This performance is crucial when reducing pixel size because reductions in size typically sacrifice sensitivity. DRS employs a patented umbrella pixel design that separates the radiation-absorbing and transducing elements of the bolometer. This separation allows for a maximum focal-plane fill factor, and the unique umbrella structure design reduces the mass and thermal time constant of the bolometer.”

DRS will begin volume production of the Tenum 640 thermal imaging module in the fourth quarter of ; Ransom notes that the module is the first uncooled (640 × 512) 10-μm-pitch thermal camera module on the market available for original equipment manufacturers (OEMs).

To simplify integration for OEMs, the module is I/O-compatible with the Tamarisk products, using the same connector and feature board. In addition, the communication protocol is the same, so OEM customers can plug a Tenum 640 into their current products and begin imaging and controlling the camera without extensive engineering changes.

Since , DRS uncooled camera modules have been used in handheld firefighting cameras, says Ransom. “Uncooled LWIR cameras give firefighters the ability to see clearly through smoke, locate and rescue victims, and identify dangerous hot spots,” he explains. “With the radiometric (temperature measurement) capability of the DRS LWIR camera module, a firefighter can determine the temperature of a ceiling or door before encountering a dangerous building collapse or entering a dangerous room.” The firefighter’s task is made easier by DRS’s Image Contrast Enhancement (ICE) algorithm (see Fig. 1).

Remote temperature measurement, including of humans

Jenoptik (Jena, Germany), which includes Jenoptik Optical Systems (Jupiter, FL), has multiple product lines of thermal imagers; its current products include the IR-TCM camera, VarioCAM handheld camera, and Blackbird Precision portable monitoring kit, which have all been designed and are calibrated to visualize heat and detect temperature anomalies in either mobile or stationary applications. In addition, Jenoptik is introducing a new line of compact uncooled thermal camera modules called EVIDIR in .

The company’s thermographic camera product line is based on VGA and XGA 17 μm amorphous silicon (A-Si) microbolometer technology, whereas the new EVIDIR products are built around VGA and QVGA 12 μm A-Si microbolometers. All of Jenoptik’s thermal cameras offer a variety of standard configuration options such as camera format, frame rate, communication interface, and lens options. “The cameras are fully functional as stand-alone devices, but IR-TCM, Blackbird, and EVIDIR have been designed to facilitate integration into OEM applications,” says G. Scott Libonate, North American director, Advanced Systems, at Jenoptik Optical Systems. “All of the OEM cameras and, in particular, the EVIDIR offer a ‘toolbox’ approach of available configuration options to facilitate OEM customization: options such as lenses, shutter, imager format, frame rate, and communication interface are modular, allowing customers to mix and match to best suit their applications.”

Libonate notes that all of Jenoptik’s thermal cameras have a high sensitivity with a temperature resolution (NETD) less than 40 mK, which allows them to distinguish relative temperature differences of a tenth of a degree or less (see Fig. 2). He adds that thermographic cameras like the Blackbird can remotely measure temperatures with an absolute accuracy of better than 2°C over a -40°–600°C temperature range (with high-temp calibration options up to °C available).

As described by Jens Vogt, head of international sales at InfraTec, the VarioCAM HD head 900 camera has a microbolometer detector with XGA ( × 768) pixel resolution, is fully radiometric over a range of -40 to °C, and has a thermal sensitivity that reaches 20 mK. “A wide range of applications benefits from those specifications,” says Vogt. “One of these is additive manufacturing, where process parameters need to be precisely set based on respective temperature measurements. Here, the camera’s subwindow ranges allow imaging at higher process speeds of up to 240 Hz.”

For higher speeds, Vogt notes that InfraTec advises the use of its ImageIR MCT-based cameras (for example, the ImageIR , with a spectral range of 7.7 to 10.2 μm, has a frame rate of up to 14,593 Hz). “As all of InfraTec’s cameras come with a wide range of lenses and specific protective windows, additive-manufacturing processes of different scales can be equipped to optimize for the very high demands in spatial resolution,” Vogt adds.

High dynamic range without gain reduction

As part of its infrared imaging portfolio, Teledyne DALSA (Waterloo, ON, Canada) produces powerful, versatile solutions from SWIR to uncooled LWIR for industrial, security, and defense applications. LWIR imagers produced by Teledyne DALSA include its Calibir GXM LWIR cameras containing uncooled IR microbolometer sensors with radiometric operations, the Calibir DXM640 LWIR camera with an uncooled IR VGA camera core, and LWIR wafer-level-packaged vanadium oxide microbolometers.

The Calibir GXM cameras have high sensitivity in the 8–12 µm spectral range and factory-calibrated radiometric performance, according to Jean Brunelle, product manager for the Calibir series. The cameras also feature both shutter and shutterless operation and rapid image output on power-up while delivering uniform response over their whole operating temperature range, all of which benefit uninterrupted image acquisition; a 21-bit ADC design maintains a high dynamic range without the need for gain reduction, leading to the best possible NETD over a temperature range of more than 600°C.

“Calibir delivers accurate, repeatable results for critical applications like detecting elevated skin temperature in fever screening (see Fig. 5),” says Brunelle. “In addition to fever screening, the Calibir GXM series benefits many other industrial monitoring applications requiring radiometric measurement, such as welding, sintering, baking, smelting, and firefighting.”

The RP Photonics Buyer's Guide contains 144 suppliers for infrared optics. Among them:

UM Optics

UM Optics is the biggest optics supplier in China. We supply CaF2, BaF2, MgF2, LiF material covering the VUV to IR spectrum. We can also deliver cut blanks, polished lens, drilled windows, spherical lenses, aspheric lenses, galvo scanning mirrors, prisms, cylindrical lenses and mirrors in very large quantities at best price. UM Optics also grows silicon material in optical grade and supplies optics like silicon wafers, mirrors, AR-coated lenses, and prisms. We are also good at ZnSe/ZnS/Ge IR material optics.

Ecoptik

Ecoptik manufactures precision infrared optical devices based on germanium, silicon, zinc selenide, zinc sulfide and other materials. Customized high-precision and complex optical devices, including short-wave infrared optical devices of many kinds can be made. Feel free to contact us!

With competitive price and timely delivery, IRLENS sincerely hope to be your supplier and partner.

OPTOMAN

OPTOMAN employs IBS technology to manufacture laser optics made for mid-IR. Broadband dispersive and low GDD mirrors for mid-IR range can reduce or even completely eliminate the need to use combinations of various bulk materials to compensate dispersion.

Cost-effective solutions for mid-IR optics are also available. By developing relatively thin coatings through advanced material research, we’ve reduced the primary cost driver — production time — while maintaining the core advantages of IBS coatings. This allows us to deliver high-quality, durable mirrors without sacrificing spectral performance or efficiency, making them an affordable choice for Mid-IR laser systems, even at power densities up to 100 GW/cm2.

Custom mid-IR optics can be designed for spectral range 1 – 5 µm, using standard or CaF2, MgF2, YAG, sapphire or silicon substrates.

IRD Glass

IRD Ceramics manufactures precision infrared optical components which are essential to infrared cameras and sensors used by homeland security, border patrol, defense and security companies. We perform all fabrication in house, allowing us to produce low-cost IR mirrors, lenses and windows for commercial applications as well as customized lenses to meet the exact demands of defense and security companies. IRD Ceramics works with sapphire, silicon, chalcogenides, germanium, BaF2, CaF2, zinc selenide and more.

EKSMA OPTICS

EKSMA Optics has substrates and finished optical components – windows, lenses and mirrors made from lithium fluoride (LiF), calcium fluoride (CaF2), barium fluoride (BaF2), sapphire (Al2O3), zinc selenide (ZnSe) and germanium (Ge) for laser and optical instruments applications in the infrared wavelength range.

Shanghai Optics

At Shanghai Optics we design and manufacture a wide variety of custom optical IR components. Our state of the art equipment allows us to achieve unparalleled precision and surface quality, and every piece we manufacture is subject to stringent quality controls.

We offer a wide range of IR substrates, including Ge, Si, ZnSe, ZnS, ZnS , CaF2, BaF2 and GaAs. Our lenses and windows are available with multiple anti-reflection coating options that can increase durability and improve performance.

Shalom EO

Shalom EO offers a wide range of infrared optics – not only singlet IR optical lenses, IR optical windows and IR domes, but also lens modules designed for MWIR (3–5 μm) and LWIR (8–12 μm) thermal imaging cameras. A variety of specific infrared optical materials are available: germanium, zinc selenide (ZnSe), zinc sulfide (ZnS), chalcogenide glass, silicon, sapphire and fluoride (CaF2, BaF2, MgF2 and LiF). Our fabrication techniques include conventional polishing and diamond turning. Moreover, multiple types of modules with flat, spherical and aspherical optical surfaces are optional for different requirements. Referring to the thermal imaging lenses, Hangzhou Shalom EO offers standard lenses and hundreds of custom free-designed lens modules (e.g. athermalized lenses, fisheye lenses, single FOV, dual FOV, zoom lenses).

Further, our infrared windows can be used at 0.75 μm to 20 μm and our infrared lenses are suitable in a wide spectral range from 700 nm to  nm. Infrared domes are suitable for 3 μm to 12 μm. AR coating options include broadband anti-reflection coatings (BBAR), long-pass anti-reflection coatings and hard diamond-like carbon (DLC) coating for application in harsh environments.

Edmund Optics

Edmund Optics offers a wide range of infrared optics, using materials like aluminum, calcium fluoride, fused silica, germanium, magnesium fluoride, sapphire, silicon, zinc selenide, zinc sulfide and other infrared materials.

Avantier

Avantier produces a wide range of high quality infrared optics, including infrared lenses, prisms, windows, mirrors, and laser and imaging assemblies. Our state-of-the-art equipment allows us to achieve unparalleled precision and surface quality, and every piece we manufacture is subject to stringent quality controls.

Vortex Optical Coatings

At Vortex we are able to manufacture custom optical coatings in the near and mid infrared regions between 900 and  nm. Whether you are looking for bandpass filters, long/short pass filters, beamsplitters, AR coatings (and many other coating types), we can apply these to a whole range of substrates, many of which we hold in stock on our shelves for immediate coating so we are able to offer very good lead times compared to the industry standard.

LightMachinery

LightMachinery has extensive expertise in the manufacturing and testing of infrared optics based on zinc selenide, zinc sulfide and germanium optics for CO2 lasers, e.g. in the form of mirrors, lenses and rhomb retarders. In addition, we have a thorough understanding of the importance of high damage threshold coatings for our laser customers.

Knight Optical

Knight Optical can offer a variety of stock and custom infrared optics, such as lenses, windows, prisms and filters. We can provide these in a wide range of different materials including germanium, silicon, zinc selenide, calcium fluoride, sapphire, magnesium fluoride, zinc sulphide. Our custom infrared optics include aspheric lenses, filters working in the IR wavelengths, and coatings optimised for the different thermal wavebands, as well as diamond-like carbon (DLC) coatings for extra durability of a surface.

UltraFast Innovations

UltraFast Innovations (UFI®) offers a varied selection of broadband infrared mirrors designed for ultrafast laser systems. For example, we provide mirrors for thulium- and holmium-based systems operating in the 2-μm spectral region, Cr:ZnS systems around 2.4 μm and Cr:ZnSe for 3.2 μm. Such mirrors can be provided with precise control of chromatic dispersion.

For more LWIR Lens for Cooled Camerainformation, please contact us. We will provide professional answers.

Sinoptix