Several development stages of low-light night vision technology

Low-light night vision technology is dedicated to exploring the acquisition, conversion, enhancement, recording and display of target image information at night and other low-light conditions. Its achievements are concentrated in the effective expansion of human vision in the time domain, space and frequency domain.

The development of low-light night vision technology was marked by the invention of the antimony-cesium (Sb-Cs) photocathode by P. Gorlich in 1936. A.H. Sommer invented the antimony potassium sodium cesium (Sb-K-Na-Cs) multi-alkali photocathode (S-20) in 1955, which brought low-light night vision technology into a substantial stage of development. The advent of fiber optic panels in 1958, coupled with the improvement in phosphor performance at that time, laid the foundation for fiber optic panel coupled image intensifiers. In 1962, the United States developed this three-stage coupled image intensifier, and used it as the core component to make the first-generation low-light night vision device, the so-called "starlight mirror"-AN/PVS-2, which was used in the Vietnam War. . The microchannel electron multiplier appeared in 1962, and the practical electron multiplier device MCP-microchannel plate image intensifier was developed in 1970. On this basis, the second generation low-light night vision device was developed. The high-sensitivity camera tube developed in the 1970s was coupled with the MCP image intensifier to create a low-light camera tube and low-light TV with better performance. The British army used it in the Falklands War in 1982 and achieved the expected night fighting effect. In 1965, J.Van Laar and J.J.Scheer made the world's first gallium arsenide (GaAs) photocathode.

In 1979, the American ITT Company developed an imaging device (sheet tube) using GaAs negative electron affinity photocathode and MCP technology, advancing low-light night vision devices to the third generation, and extending the working band to long wavelengths. The electron bombardment silicon target (EBS) camera tube and secondary electron conductance (SEC) camera tube developed in the 1960s were coupled with image intensifiers to produce the first generation of low-light camera tubes. Since the 1980s, due to the development of charge-coupled devices (CCD), new low-light imaging devices have been emerging. The image intensifier is coupled with the CCD through an optical fiber panel to create a solid-state self-scanning low-light camera component and a new low-light TV with it as the core.

The first generation of low-light night vision technology

In the early 1960s, based on the invention of multi-alkali photocathode (Sb-Na-K-Cs), optical fiber panel and the improvement of concentric sphere electronic optical system design theory, these three major technologies were engineered and developed into The first generation of low-light tubes. Its first-level single tube can achieve about 50 times brightness gain, and through three-level cascade, the gain can reach 5*104~105 times. The first generation of low-light night vision technology is a passive observation method, which is characterized by good concealment, small size, low weight, high yield, and easy mass production; it technically takes into account and solves the problem of flat field and concentric sphere of the optical system. The electronic optical system requires a contradiction between spherical object (image) surfaces, and the imaging quality is significantly improved. Its disadvantage is that it is afraid of strong light and has halo phenomenon.

Second generation low-light night vision technology

The main feature of the second generation of low-light night vision devices is the invention of the microchannel plate electron multiplier (MCP) and its introduction into a single-stage low-light tube. A one-stage micro-light tube equipped with one MCP can achieve a brightness gain of 104-105, thus replacing the original large and bulky three-stage cascade first-generation micro-light tube; at the same time, the inner wall of the MCP microchannel plate actually It is a continuous dynamo stage with a fixed plate resistance. Therefore, under a constant operating voltage and with a strong current input, there is a self-saturation effect of a constant output current. This effect just overcomes the halo phenomenon of the low-light tube; in addition, its Smaller in size and lighter in weight, the second-generation low-light night vision device is currently the main body of domestic low-light night vision equipment.

Super second-generation low-light night vision technology

The ultra-second-generation low-light tube adopts roughly the same structure as the third-generation low-light close-in tube. The main technical feature is to introduce high-sensitivity multi-alkali photocathode into the second-generation low-light tube and borrow the technology from the third-generation micro-light tube. The results of mechanism and process research on optical MCP, tube structure, integrated power supply, crystallography, and semiconductor body characteristics have greatly improved the imaging quality. Because the process is relatively simple and the price is relatively low, it has become a current mainstream product.

Third generation low-light night vision technology

The main feature of the third generation of low-light night vision devices is the introduction of transmissive GaAs photocathode and MCP with Al2O3 and ion barrier film into the close-fitting low-light tube. Compared with the second-generation low-light devices, the sensitivity of the third-generation low-light devices has increased by 4-8 times, reaching 800μA/Im~2600μA/Im, the lifespan has been extended by 3 times, and the spectrum utilization of night sky light has been significantly improved. Target sight range at dark (10-4lx) nights is extended by 50%-100%. The technological basis of the third-generation micro-light device is ultra-high vacuum, NEA surface activation, double proximity contact, double indium sealing, surface physics, surface chemistry and long-life, high-gain MCP technology, etc., which also provides the basis for the development of the fourth-generation micro-light tube. and long-wave infrared photocathode image intensifiers and other high-tech products have created good conditions.

Fourth generation low-light night vision technology

The designer of the low-light tube removed the ion barrier film from the MCP to obtain a film-free low-light tube. At the same time, an automatic door switching power supply was added to control the switching speed of the photocathode voltage, and the low-halo imaging technology was improved to help To enhance visual performance under strong light.

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