| 1 | Uncooled Microbolometer Thermal resistance-based detector array | Long-wave infrared (LWIR): approximately 8–14 µm | Operates near ambient temperature. Incoming infrared radiation changes the electrical resistance of tiny thermally sensitive elements, commonly made with vanadium oxide or amorphous silicon. | Typical array formats range from 160 × 120 to 1280 × 1024 pixels. Common thermal sensitivity is approximately 30–80 mK NETD, depending on optics, integration time, calibration, and environmental conditions. Frame rates commonly range from 9 to 60 Hz. | Building inspection Predictive maintenance Firefighting Automotive night vision Security monitoring Industrial process checks | Low size, weight, power, and cost; no cryogenic cooler; suitable for continuous operation; detects emitted heat without visible light. | Lower sensitivity, dynamic range, and high-speed performance than cooled photon detectors. Measurements can be affected by emissivity, reflected radiation, atmospheric conditions, and sensor drift. |
| 2 | Cooled MWIR Photon Detector Typically indium antimonide (InSb) or mercury cadmium telluride (MCT) | Mid-wave infrared (MWIR): approximately 3–5 µm | Uses semiconductor photon detection and is commonly cooled to approximately 77 K or another cryogenic operating temperature to reduce dark current and thermal noise. | High sensitivity and fast response. High-speed systems can support hundreds of frames per second, while specialized systems may operate faster. NETD can be below 25 mK under suitable laboratory and optical conditions. | High-speed thermal imaging Gas-leak visualization Combustion research Military and aerospace imaging Scientific radiometry Hyperspectral imaging | Excellent sensitivity, fast shutter speeds, strong performance for hot targets, and good discrimination of temperature differences. | Requires a cooler, increasing cost, power consumption, acoustic output, warm-up time, and maintenance complexity. MWIR transmission can be affected by atmospheric absorption and humidity. |
| 3 | Cooled LWIR Photon Detector Commonly MCT or quantum-well-based technology | Long-wave infrared (LWIR): approximately 8–12 or 8–14 µm | Photon-sensitive semiconductor array operated at cryogenic temperature. Cooling reduces dark current and enables high detectivity in the long-wave band. | Very high sensitivity for small temperature differences. Typical systems provide 320 × 256, 640 × 512, or larger formats, with NETD often below 25 mK under optimized conditions. Frame rates may range from tens to several hundred hertz. | Long-range surveillance Low-temperature target detection Astronomy Remote sensing Precision thermography Hyperspectral research | High detectivity in the atmospheric LWIR window, excellent low-contrast target detection, and strong performance for quantitative thermal measurement. | Cryogenic cooling adds size, weight, power consumption, cost, vibration, and system complexity. It is generally less practical for compact consumer and battery-powered products. |
| 4 | Standard InGaAs SWIR Sensor Indium gallium arsenide focal-plane array | Short-wave infrared (SWIR): approximately 0.9–1.7 µm | Photon detector that is usually operated uncooled or thermoelectrically cooled. It detects reflected or transmitted SWIR radiation rather than primarily measuring long-wave thermal emission. | Common formats include 320 × 256, 640 × 512, and 1280 × 1024 pixels. Typical frame rates range from 30 to more than 100 Hz, depending on format and readout design. Often provides low dark noise at room temperature. | Machine vision Semiconductor inspection Laser-beam monitoring Moisture and sorting analysis Solar-cell inspection Surveillance in haze | Good compatibility with optical materials and lasers used near 1.0–1.55 µm; sees through some silicon-based materials and offers useful contrast in haze, smoke, and low-light conditions. | It is not a direct substitute for LWIR thermal imaging. Performance depends strongly on available illumination or active illumination, and sensitivity typically falls near the long-wavelength cutoff. |
| 5 | Extended-SWIR InGaAs Sensor Long-cutoff InGaAs focal-plane array | Extended short-wave infrared: approximately 0.9–2.2 or 2.6 µm | Uses an InGaAs alloy engineered for a longer wavelength response. Thermoelectric cooling is often used because longer-cutoff material can have higher dark current. | Common formats range from 320 × 256 to 1280 × 1024 pixels. Typical operation is from 30 to 100 Hz, depending on array size and cooling. Sensitivity generally decreases as the cutoff wavelength is extended. | Plastic and polymer inspection Food and agricultural sorting Pharmaceutical inspection Mineral identification Moisture detection Chemical process monitoring | Provides access to useful absorption features beyond 1.7 µm, where many organic materials, coatings, moisture levels, and chemical compositions show stronger spectral contrast. | Usually has higher dark current, greater cooling requirements, and lower sensitivity than standard InGaAs. It remains primarily a reflected-light or transmitted-light imaging technology rather than a conventional thermal camera. |
| 6 | Quantum-Well Infrared Photodetector (QWIP) Quantum-well semiconductor focal-plane array | Commonly LWIR: approximately 8–10 µm; wavelength response is design-specific | Uses intersubband transitions in quantum wells. The array normally requires cryogenic cooling to suppress dark current and achieve practical sensitivity. | Spectrally uniform arrays and highly repeatable pixel behavior are possible. Typical formats include 320 × 256 and 640 × 512 pixels. Performance depends strongly on the well structure, operating temperature, optics, and readout circuit. | Multispectral thermal imaging Hyperspectral research Space-based remote sensing Stable radiometric measurements Research instrumentation | Good pixel-to-pixel uniformity, stable spectral response, and the ability to engineer the response around selected infrared bands. | Requires cryogenic cooling, has lower quantum efficiency than some competing photon detectors, and can be less flexible for broadband imaging. It is more common in specialized systems than in general-purpose thermal cameras. |
| 7 | Thermopile Array Thermoelectric detector array | Broadband infrared, often approximately 2–14 µm depending on absorber and optical filter | Measures the voltage generated by multiple thermocouples when absorbed infrared energy creates a temperature difference. Operates without cryogenic cooling and generally without active cooling. | Typical arrays range from a few pixels to approximately 32 × 32 or higher in specialized designs. Frame rates are commonly lower than those of microbolometers, often around 1–30 Hz. Sensitivity is suitable for presence, temperature-pattern, and low-resolution thermal measurement. | Occupancy detection HVAC control Contactless temperature measurement Appliance monitoring Smart building systems Low-cost people counting | Very low power consumption, simple electronics, broad spectral response, long operating life, and suitability for compact embedded products. | Lower spatial resolution, slower response, and lower thermal sensitivity than most microbolometer arrays. Accuracy is affected by field of view, emissivity, ambient temperature, and calibration. |