Jan 07, 2025
The imaging principle of infrared thermal imaging technology is that the infrared radiation emitted by objects is imaged on the focal plane through the optical system. The photosensitive elements convert the received light signals into electrical signals, which are then processed through amplification, sampling, and other steps and sent to the display system to form an infrared image. Each pixel within the infrared focal plane array corresponds to a sensitive element, which is key to achieving the detection of scenes within the entire field of view.
The infrared focal plane array (Focal Plane Array, FPA) is the core component of an infrared imaging system, and its performance directly affects image quality and application effectiveness. According to different classification methods, infrared focal plane arrays can be divided into various types, each with its unique characteristics and application scenarios.
Cooled and Uncooled Infrared Focal Plane Arrays
Based on different operating temperatures, infrared focal plane arrays can be divided into cooled and uncooled types. Cooled infrared focal plane arrays need to work in low-temperature environments, typically using liquid nitrogen or electric coolers for cooling. Low-temperature environments can significantly reduce the thermal noise of the detectors, thereby improving detection sensitivity and image quality. Cooled infrared focal plane arrays are mainly used in high-precision, high-sensitivity fields such as military reconnaissance, astronomical observation, and scientific research. Uncooled infrared focal plane arrays, on the other hand, operate at room temperature and do not require additional cooling equipment, boasting advantages such as small size, light weight, and low power consumption. Although the detection sensitivity and image quality of uncooled infrared focal plane arrays are relatively lower, their lower cost makes them suitable for the civilian market, such as security monitoring, vehicle night vision, and industrial inspection.
Photon Detectors and Thermal Detectors
Based on the principle of interaction between optical radiation and materials, infrared focal plane arrays can be divided into photon detectors and thermal detectors. Photon detectors detect infrared radiation by absorbing infrared photons to generate electron-hole pairs. Common photon detector materials include indium gallium arsenide (InGaAs), mercury cadmium telluride (HgCdTe), and indium antimonide (InSb). Photon detectors have the characteristics of high sensitivity and rapid response, suitable for high-resolution and high-frame-rate infrared imaging applications. Thermal detectors, on the other hand, detect infrared radiation by absorbing it, causing a temperature change that alters the material's resistance, capacitance, or voltage. Common types of thermal detectors include thermopiles, pyroelectric detectors, and bolometers. While thermal detectors have slower response speeds, their simple manufacturing process and lower cost make them suitable for low-cost, large-scale infrared imaging applications.
Short-Wave, Mid-Wave, and Long-Wave Infrared Focal Plane Arrays
Based on different detection wavelengths, infrared focal plane arrays can be divided into short-wave (SWIR), mid-wave (MWIR), and long-wave (LWIR) categories. Short-wave infrared focal plane arrays typically operate in the 0.9-1.7 micron band, suitable for imaging under low-light conditions such as night vision and near-infrared spectroscopy. Indium gallium arsenide (InGaAs) is the primary material for short-wave infrared detectors, known for its high sensitivity and high resolution. Mid-wave infrared focal plane arrays operate in the 3-5 micron band, suitable for detecting and imaging high-temperature targets such as fire monitoring, industrial furnace inspection, and missile guidance. Mercury cadmium telluride (HgCdTe) and indium antimonide (InSb) are the main materials for mid-wave infrared detectors, characterized by high detection sensitivity and rapid response. Long-wave infrared focal plane arrays operate in the 8-14 micron band, suitable for detecting and imaging targets within the human body temperature range, such as body temperature monitoring, building heat loss detection, and environmental monitoring. Common materials for long-wave infrared detectors include vanadium oxide (VOx) and amorphous silicon (a-Si), known for their high thermal sensitivity and stability.
Infrared focal plane arrays have been widely used in security surveillance, industry, outdoor night vision, and other fields, possessing enormous market potential and application prospects. In the future, the development directions of infrared focal plane arrays mainly include the following aspects: First, large array sizes. By increasing the number of photosensitive elements, higher resolution and a broader field of view can be achieved to meet the demand for details and range in different application scenarios. Second, miniaturization. Lightweight and easy to carry is an important development direction. By optimizing design and structure, the volume of the device can be reduced, enhancing portability. Third, dual-color and multispectral techniques. By using various filters with different wavelengths on the photosensitive elements, different bands of infrared radiation can be detected, improving the sensitivity and adaptability of the detector. Fourth, high-temperature performance. By researching new materials and fabrication processes, the performance stability and reliability of detectors under high temperatures can be increased. Lastly, intelligentization. With the development of artificial intelligence and big data technology, infrared thermal imaging technology can be combined with other sensors and data processing systems to achieve more precise and intelligent night vision observation and infrared temperature measurement functions.
