What is the black body in the infrared camera

What is the black body in the infrared camera

We will often see the description of the built-in black body in the infrared camera products, so what exactly is a black body?

First of all, we need to understand, why do infrared cameras use blackbody? Scientists have found that in nature, as long as objects above -273.16°C emit heat radiation, this heat radiation is related to the object's own temperature, and this emitted radiation energy will always hit some objects. When the thermal radiation hits the detector in the thermal imaging camera, it is amplified by the amplifier in the instrument and the data is processed.

The data received at this time is affected by objective factors such as the radiation of the target itself, the reflected radiation of the target to the surrounding environment, the attenuation of the radiation in the atmosphere, the size of the object, etc. The thermal image also only gives a qualitative description of the radiation temperature of the surface of the object. If you want to obtain the absolute temperature of the object through the thermal image, you must calibrate the absolute temperature value by comparing with the thermal image of the reference object. There are two methods to calibrate the thermal imager. One is to convert the radiant energy of the measured target into temperature, and the other is to compensate the internal radiation of the thermal imager.

The most widely used calibration method is to use a black body at a fixed short distance, using a high-precision black body as the standard. In order to establish the relationship between the amount of radiation and the temperature, the black body is set at different temperatures, and the measurement results are fitted to the precise temperature value of the black body to obtain the calibration curve.

What is the black body? A black body is a device that calibrates an infrared camera. When the thermal radiation of an object hits the object, only three situations occur, either absorption, transmission or reflection. Scientists call an object that can fully absorb radiant energy a "black body" with a surface emissivity of 1. The black body studied in the laboratory is divided into a cavity radiation source and a surface radiation source, and the emissivity is generally close to 1, which can be corrected by a correction formula.

Then, the thermal imaging camera can use the change law of black body radiation to measure the absolute temperature of the object.

Reference materials:

李云红. 基于红外热像仪的温度测量技术及其应用研究[D]. 哈尔滨工业大学. 2010.

胡 蝶. 红外热像仪的测量技术及其应用研究[D]. 广东工业大学. 2019.