Uncooled infrared technology

All objects in nature with temperatures above absolute zero (-273°C) emit infrared radiation, and infrared image sensors convert the detected infrared radiation into image information visible to the human eye.

Infrared imaging technology covers infrared optics, materials science, electronics, mechanical engineering technology, integrated circuit technology, image processing algorithms and many other technologies. The core of the infrared imaging device is the infrared focal plane detector.

Principles of uncooled infrared technology

Uncooled infrared detectors utilize the thermal effect of infrared radiation and use infrared absorbing materials to convert infrared radiation energy into heat energy, causing the temperature of the sensitive element to rise. A certain physical parameter of the sensitive element changes accordingly, and is then converted into an electrical signal or a visible light signal through a designed conversion mechanism to achieve detection of the object.

Pyroelectric type

Infrared radiation changes the temperature of the material, causing the spontaneous polarization intensity of the material to change, and induced charges appear on the two crystal planes perpendicular to the direction of spontaneous polarization. The intensity of radiation is detected by measuring the amount of induced charge or voltage. Pyroelectric infrared detectors are different from other detectors in that they only output signals during the temperature rise and fall process, so the infrared radiation must be modulated when using pyroelectric detectors.

thermopile

A closed loop composed of two conductor materials with different work functions. When the temperatures at the two contact points are different, the temperature gradient causes the carriers inside the material to move to the lower temperature end, forming charges at the lower temperature end. Accumulate, a thermoelectric potential will be generated in the loop.

Diode type

The use of semiconductor PN junction has good temperature characteristics. Different from other types of uncooled infrared detectors, the temperature detection unit of this infrared detector is a single crystal or polycrystalline PN junction, which is fully compatible with the CMOS process, easy to be integrated into a single chip, and is very suitable for mass production.

Thermistor type (microbolometer)

The resistance of the thermistor changes with temperature to detect the intensity of radiation. Generally, the detector adopts a cantilever beam structure. The photosensitive element absorbs infrared thermal radiation. The readout circuit measures the current change caused by the change in resistance of the thermosensitive material. The electrical signal is collected, analyzed and read out through the readout circuit. Detectors are generally vacuum sealed to ensure good thermal insulation.

• Previous: Application of germanium in infrared optics industry
• Next: Routine maintenance and guarantee of monocular low-light night vision device