Longwave infrared thermography, as an advanced non-contact temperature measurement and thermal imaging device, plays a crucial role in many fields. However, in recent years, with the technological breakthroughs and popularization of shortwave infrared detectors, shortwave infrared temperature measurement has gradually been added in some industries to increase the accuracy and compatibility of temperature measurement. Below is the description of differences:

1、 Principle

Shortwave infrared: Use shorter wavelengths (usually around 1-3 μm) of infrared radiation to capture the heat distribution of an object. By detecting and measuring the shortwave infrared radiation emitted by objects, thermal images are generated. The imaging principle is similar to visible, and it has a good temperature measurement effect on high-temperature objects. In some applications, it can provide higher resolution and more accurate temperature information, such as metal smelting, mineral raw material smelting, laser welding, etc.

Long wave infrared: Use longer wavelength (usually 8-14 μm) infrared radiation to generate thermal images. By detecting and measuring the long wave infrared radiation emitted by an object, the heat distribution is displayed. Based on the thermal radiation characteristics of the object itself, objects at different temperatures will exhibit different radiation intensities in the long wave infrared band, which can be used to measure the temperature of the object.

2、 Detector Technology

Shortwave infrared: InGaAs, as a mature material for shortwave infrared detectors, has been verified to have good dynamic response and accuracy in some high-temperature detection scenarios even with high cost. The LUMIDAR_SW series of shortwave infrared image sensors launched by LUMIDAR has a 16 bit Grayscale, 60% quantum efficiency, and excellent signal-to-noise ratio, making it very suitable for high-temperature detection scenarios. At the same time, it combines disruptive organic semiconductor technology and mature CMOS processes to significantly reduce manufacturing costs.

Longwave infrared: The detector material is generally vanadium oxide, silicon doped (or polycrystalline silicon), etc. These materials have good response characteristics in the long wave infrared band and can convert the received long wave infrared radiation into electrical signals. Long wave infrared thermal imaging systems typically use uncooled detectors, which reduce cost and system complexity, making them more portable and user-friendly. However, in some situations where high temperature measurement accuracy and resolution are required, cooled long wave infrared detectors are also used.

3、 Measurement range and accuracy

Shortwave infrared temperature measurement: suitable for temperature measurement of high-temperature objects, such as in industrial high-temperature process monitoring, metal smelting and other fields. For objects with temperatures above several hundred degrees or even higher, stable and accurate temperature measurement can be achieved, and it has a fast response speed. However, the temperature measurement effect for low-temperature objects is relatively poor, and the temperature measurement range is relatively narrow. Generally, high measurement accuracy can only be guaranteed within a specific high-temperature range.

Longwave infrared: With a wide temperature measurement range, it can cover temperatures from room temperature to several hundred degrees Celsius or even higher, meeting the temperature measurement needs of most conventional objects. It is widely used in fields such as construction, electricity, and healthcare. For example, it can be used to detect the thermal effects of buildings to discover building defects (such as insulation problems, leaks, etc.), monitor the heating of electrical equipment to prevent faults, assist in medical diagnosis (such as detecting local temperature anomalies in the human body), etc. However, for the measurement of high-temperature objects, especially when the temperature exceeds a certain threshold (such as 1000 ℃ or above), its accuracy may be affected to some extent, and the response speed may decrease compared to short wave infrared imaging temperature measurement.

4、 Environmental adaptability

Shortwave infrared: Due to its short wavelength, it is relatively affected by environmental factors such as water vapor and dust when propagating in the atmosphere. Under adverse weather conditions (such as rain, heavy fog, dust, etc.), its measurement effect and imaging quality may be affected to a certain extent. But for certain specific environments, such as the presence of smoke, dust, etc., shortwave infrared has a certain penetration ability and can obtain clearer images than visible.

Longwave infrared: The propagation of longwave infrared in the atmosphere is relatively less affected by environmental factors, and it can maintain good stability and reliability under different weather conditions. It has strong environmental adaptability and can be used in various environments such as indoor and outdoor.

5、 Imaging characteristics

Shortwave infrared: Imaging is closer to visible images, which can present the details and contours of objects. The clarity and resolution of the image are relatively high, which has advantages for applications that require precise recognition of object shape, structure, or specific features. However, due to its relative sensitivity to changes in object emissivity, it is necessary to more accurately determine the emissivity parameters of the object in practical applications to improve the accuracy of temperature measurement.

Longwave infrared: Imaging mainly reflects the thermal distribution of an object. Different colors in the image represent different temperatures of the object, which can intuitively display the differences and trends in surface temperature of the object. However, in terms of image details and resolution, it may be slightly lower than short wave infrared imaging. However, long wave infrared thermal imaging is relatively less sensitive to changes in object emissivity, and the requirements for determining emissivity parameters are relatively low in practical applications.

The above are the main differences between these two temperature measurement techniques, and corresponding solutions should be selected according to different application scenarios. In addition, in some harsh on-site environments and situations where high temperature measurement accuracy is required, two temperature measurement schemes may even be embedded simultaneously in a temperature measurement system to achieve the expected temperature monitoring effect.