What is the core of refrigeration thermal imaging?

(1) Refrigeration detector

Core position: The core of the cooled thermal imaging equipment is the cooled detector. Its main function is to convert the received infrared radiation signals into electrical signals, and in order to be able to detect weak thermal signals, the detector needs to be cooled to an extremely low temperature. For example, cooled detectors in some military applications can operate at temperatures as low as 77K (liquid nitrogen temperature) or lower.

Detection principle: When the material in the detector is in a low temperature environment, the internal thermal noise will be significantly reduced, allowing the detector to more sensitively sense the tiny physical changes caused by infrared radiation. For example, mercury cadmium telluride (HgCdTe) detectors can produce a more effective photoelectric effect for infrared photons at low temperatures. When infrared radiation hits the detector material, the rate of electron-hole pair generation in the material is proportional to the intensity of the infrared radiation. Proportional, thus converting thermal signals into electrical signals, providing the basis for subsequent imaging.

(2) Refrigeration system

Function and necessity: The refrigeration system is a key part in maintaining the low temperature working environment of the detector. Since the detector needs to work at low temperatures to achieve high sensitivity and high resolution, the refrigeration system must be able to effectively remove the heat generated by the detector and the heat transmitted from the outside. For example, a refrigeration system using a Stirling cooler can achieve refrigeration through periodic compression and expansion of gas to cool the detector to the required low temperature.

Working principle and composition: The refrigeration system is mainly composed of a compressor, an expander, a cold head and heat dissipation components. The compressor compresses the refrigerant gas to increase its pressure and temperature, and then transports the high-temperature and high-pressure gas to the expander through a pipeline. In the expander, the gas expands and does work externally, and its own temperature drops sharply. The cold head is closely connected to the detector, transferring the cold energy to the detector to cool it down. At the same time, the heat dissipation components dissipate the heat generated during the refrigeration process into the surrounding environment to ensure the continuation of the refrigeration cycle.

(3) Signal processing and amplification unit

Importance of signal processing: In cooled thermal imaging, the electrical signal output by the detector is very weak, and the signal processing and amplification unit plays a vital role. It can perform a series of processes such as amplification, filtering, and noise reduction on the electrical signals generated by the detector, converting weak signals into effective signals that can be used by subsequent imaging systems.

Specific operation content: First, the signal strength is increased to an appropriate level through an amplifier, and a filter is used to remove high-frequency noise and interference components in the signal. For example, by setting a suitable cutoff frequency, the electronic noise of the detector itself and the electromagnetic interference signals in the environment can be filtered out. Then, an analog-to-digital converter (ADC) is used to convert the analog signal into a digital signal, providing a data basis for subsequent digital image processing.

(4) High-precision optical system

Function of optical system: High-precision optical system is another core element of cooled thermal imaging equipment. It is responsible for collecting infrared radiation emitted by the target object and focusing it onto the detector. Since cooled thermal imaging equipment is usually used in situations where high accuracy and resolution are required, the quality of the optical system directly affects the imaging effect.

Optical component requirements: Lenses, reflectors and other components in the optical system need to be made of materials with high transmittance in the infrared band, such as germanium (Ge), zinc sulfide (ZnS), etc. At the same time, the processing and assembly accuracy of these components must meet very high standards to reduce optical defects such as aberration and chromatic aberration, ensuring that infrared radiation can be accurately focused on the sensitive area of the detector, thereby achieving clear and accurate thermal imaging. .

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