Detailed Explanation of Infrared Thermal Imaging Technology
Infrared thermography is a non-contact imaging technique based on the infrared radiation of an object itself. By capturing the temperature distribution of the target surface (wavelength 3-14 μ m), a visual thermal map is generated to reflect the thermodynamic state of the object. The following will be discussed from four dimensions: principles, technology classification, applications, and trends:
I. Core Principles and Imaging Mechanisms
Fundamentals of Radiation Detection
All objects with temperatures above absolute zero emit infrared radiation, and thermal imagers receive infrared energy in the 3-14 μ m wavelength band through microbolometers (such as vanadium oxide detectors), convert it into electrical signals, and reconstruct it into a pseudo color heatmap. The color differences in the heatmap directly correspond to temperature gradients (red/yellow in high-temperature areas and blue/green in low-temperature areas).
Passive imaging characteristics: No external light source required, relying on the target's own thermal radiation.
Penetration ability: It can penetrate smoke, dust, and some non-metallic materials, but cannot penetrate metals and mirror reflective layers.
Differences from structural images
Characteristic infrared thermal imaging X-ray/CT/B-ultrasound
Detecting the functional metabolism (temperature distribution) and organizational structure (morphological changes) of the object
Safety: No radiation, non-invasive. There is a risk of ionizing radiation
Early warning of temperature changes before the formation of lesions (such as tumors) depends on the detection of structural abnormalities
For example, inflammatory areas exhibit high temperature characteristics due to increased blood flow, while ischemic tissue shows abnormal low temperature.
II. Technical classification and system composition
Band division and application focus
Near infrared (0.76-1.5 μ m): used for night vision and biometric recognition, requiring active light source assistance.
Mid infrared (3-5 μ m): Industrial flaw detection, gas leak detection.
Long wave infrared (8-14 μ m): the main wavelength band for human body temperature imaging, suitable for the peak radiation of objects at room temperature.
Key hardware components
Detector: Non cooled type (vanadium oxide/polycrystalline silicon) dominates the civilian market, while cooled type (indium antimonide) is used in military high-precision scenarios.
Optical lens: germanium crystal lens (infrared transmittance>90%), surface coated with anti reflective film to reduce scattering.
Processing unit: DSP chip realizes real-time FFT noise reduction, with a temperature resolution of up to 0.03 ° C.
III. Core application scenarios
Medical diagnosis
Early screening: the temperature of the focus area of breast cancer is 1 – 3 ° C higher than that of healthy tissue, which is half a year earlier than that of structural imaging.
Pain localization: The nerve compression area shows a high temperature in a cord like pattern, while the muscle ischemia area shows low temperature.
Visualization of Traditional Chinese Medicine: The physical constitution of cold and heat deficiency and excess is visually presented through the distribution of body surface temperature (such as low temperature in hands and feet in patients with yang deficiency).
Industrial and Security
Equipment pre maintenance: Electrical connector overheating warning (>70 ° C threshold) to avoid short circuit accidents.
Security monitoring: pedestrian tracking at night (thermal characteristics are not affected by lighting), forest fire tracing and positioning accuracy ± 5 meters.
Research and Innovation
Material stress analysis: Layered defects in composite materials lead to abnormal local heat dissipation.
Building Energy Efficiency Assessment: Rapid Scanning of External Wall Heat Leakage Points.
IV. Technological Evolution Direction
Multispectral Fusion: Combining visible light and shortwave infrared (SWIR) to enhance complex environmental target recognition.
AI intelligent diagnosis: Convolutional neural network (CNN) automatically annotates abnormal areas in the heatmap, reducing the false alarm rate by 35%.
Miniaturization integration: External thermal imaging module for mobile phones (such as FLIR ONE), reducing costs to thousands of yuan.
Infrared thermal imaging is penetrating from professional fields into consumer electronics and IoT terminals, and its advantages of non radiative and functional imaging will continue to expand into smart healthcare and Industry 4.0 scenarios.
