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What is an Infrared Focal Plane Array (FPA)?

What is an Infrared Focal Plane Array (FPA)?

Issue Time:2021-09-30
a detailed introduction to the principle and classification of infrared Focal Plane Arrays
As a milestone in the development of infrared detection technology, infrared Focal Plane Array technology is rapidly expanding to new application areas and markets. It has penetrated into commercial fields such as industrial monitoring and detection, law enforcement, security, medical treatment, remote sensing, and equipment, and has changed the situation of major military applications for a long time. The following is a detailed introduction to the principle and classification of infrared Focal Plane Arrays.

Principle of Infrared Focal Plane Array

An array of photosensitive elements is arranged on the focal plane of the focal plane detector, and the infrared rays emitted from infinity are imaged on these photosensitive elements on the focal plane of the system through the optical system. The detector converts the received light signals into electrical signals and performs integral amplification and sampling, and finally sent to the monitoring system to form an image, through the buffering and multiplex transmission system, 

Infrared Focal Plane Array classification

1. Divided according to the refrigeration method

According to the cooling method, the infrared Focal Plane Array can be divided into the cooling type and uncooling type. The refrigerated infrared focal plane currently mainly adopts Dewar/quick start throttling refrigerator integrated body and Dewar/Stirling cycle refrigerator integrated body.

Since the contrast between the background temperature and the detection temperature will determine the ideal resolution of the detector, it is necessary to greatly reduce the background temperature in order to improve the accuracy of the detector. 

The detection rate of the current refrigerated detector and the uncooled detector differs by two orders of magnitude. Not only that, but their other properties are also very different. The response speed of the former is microseconds, while the latter is milliseconds.

2. Divided according to the principle of interaction between light radiation and matter

Under this condition, infrared detectors can be divided into two categories: photon detectors and thermal detectors. Photon detectors are based on the principle of the photoelectric effect caused by the interaction of photons and matter.

They include photoelectron emission detectors and semiconductor photodetectors. They are characterized by high detection sensitivity, fast response speed, and detection of wavelengths. Photon detectors generally work at lower ambient temperatures and require refrigeration devices.

Thermal detectors are a class of detectors based on the thermal effect principle of light radiation, including radiometric thermocouples or thermopiles made using thermoelectric effects, and radiometric thermistors made using the sensitivity of object resistance to temperature. The feature of this type of detector is non-selective detection, but most of them work at room temperature.

3. Divided according to the structural form

The infrared Focal Plane Array device is composed of an infrared detector array part and a readout circuit part. Therefore, according to the classification of the structure, the infrared focal plane can be divided into two types: monolithic and hybrid.

Among them, the monolithic type is concentrated on a silicon substrate, that is, the readout circuit and the detector both use the same material. Hybrid means that the infrared detector and the readout circuit use two materials respectively. For example, the infrared detector uses HgCdTe and the readout circuit uses Si. Hybrid types are mainly divided into flip-chip and Z-plane types.

4. Divided by imaging method

Infrared Focal Plane Arrays are divided into two types: scanning type and staring type. The difference is that the scanning type generally uses time-delay integration (TDI) technology to read electrical signals in a serial manner; the condensing type uses a two-dimensional form to form one image, without delay integration, the electrical signal is read in parallel. The staring imaging speed is faster than the scanning imaging speed, but it requires a high cost and the circuit is also very complicated.

5. Divided by wavelength

Due to the use of satellites and other space tools to detect targets on the surface of the earth through the atmosphere, only infrared rays passing through the atmosphere can be detected. People discovered three important atmospheric windows: 1mm-3mm short-wave infrared, 3mm-5mm mid-wave infrared, and 8mm-14mm long-wave infrared, resulting in three different wavelength detectors.

The core of the LWIR thermal imaging camera designed by JAVOL uses a high-quality uncooled Focal Plane Array, which can not only respond to changes in the frequency of the real-time sensor but also adjust the signal deviation. If you want to know more about infrared Focal Plane Arrays after reading the above, you can get a comprehensive solution by contacting us.

As a professional manufacturer of infrared thermal imaging systems, we have a professional and experienced R&D team that can develop products that meet the needs of users. We have also established a strict quality inspection system and a comprehensive management team, which can comprehensively control the quality of the products. We can also provide professional one-stop service and effective solution technology according to the diverse needs of customers. If you want to buy our LWIR thermal imaging camera, please contact us immediately!
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