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Temperature measurement distance of infrared thermal camera

The reason why the infrared thermal camera can be used for temperature screening is that it can convert temperature into visual images, and the pixels in each thermal image are temperature points. The number of temperature points is related to the device's own infrared pixels. For example, there are 110,000 temperature points in one thermal image, which is equivalent to using 110,000 thermometer guns to measure temperature simultaneously, significantly improving efficiency.

The fixed infrared thermal imaging temperature detection system is usually deployed at the entry and exit gates of transportation hubs. It has high accuracy (can achieve within ±0.2℃), a wide field of view, and a long detection distance, which can support up to 10 meters. At the same time, it can detect around 10 targets. In order to ensure the accuracy of detection, the fixed infrared thermal imaging temperature detection system is usually equipped with a constant temperature "blackbody" that is consistent with normal human body thermal radiation energy as a reference standard for real-time calibration. Currently, the price of fixed infrared thermal imaging temperature monitoring equipment is relatively high, usually costing more than ten million yuan.

The handheld infrared thermal imaging temperature measurement device can perform one-to-one or one-to-many detections, but the detection accuracy (some errors are greater than ±0.5℃), field of view, and detection distance (some are only 0.5m) are mostly lower than the fixed and mobile infrared measurement devices.

The infrared thermal imaging temperature checking door is similar to the fixed infrared thermal imaging temperature detection system, but the detection accuracy and detection distance are lower.

Factors affecting infrared thermal camera temperature measurement

Lens focal length

The most important factor determining the temperature measurement distance of the infrared thermal camera is the lens focal length. The focal length directly determines the size of the image formed by the target. The larger the focal length, the farther the imaging distance and the smaller the field of view. In simple terms, the larger the focal length, the farther the thermal imager can see, but the horizontal field of view becomes smaller.

To measure the temperature of an object with an infrared thermal camera, the object needs to be guaranteed to have more than 9 pixels in the thermal imager, otherwise, it cannot achieve the temperature measurement effect.


The infrared thermal camera currently on the market is divided into five levels of resolution: 80*60, 160*120, 384*288, 640*480, 1024*768, among which the middle three levels are the most commonly used. As mentioned earlier, to measure temperature, it is necessary to ensure that 9 pixels are reached. This means that the resolution and temperature measurement range have a great impact, and they are directly proportional to each other.

Detector performance

The lens focal length theoretically determines the detection distance of the thermal imager, and another important factor that plays an important role in practical applications is the detector performance. The focal length only determines the size of the image formed, the number of pixels occupied, and the detector performance determines the image quality, such as blur, signal-to-noise ratio, etc. Detector performance can be analyzed from pixel size, thermal sensitivity, and signal processing. The smaller the pixel size, the smaller the spatial resolution, and the greater the detection distance. The thermal sensitivity and signal processing of the detector determine the clarity of the image. If the thermal sensitivity of the detector is not high, a method of increasing the aperture of the lens can be used to improve the image quality.