When it comes to night vision devices, most people think of image enhancement technology. In fact, image enhancement systems - commonly known as night vision devices (NVDs). There is an image intensifier tube in the NVD, which can be used to collect and amplify infrared and visible light. This is how image enhancement systems work: A traditional lens called an objective captures ambient light and some near-infrared light. The collected light is sent to the image intensifier tube. In most NVDs, the power supply system for the image intensifier tube draws power from two N-Cl or "AA" batteries. The pipe will output a high voltage of about 5000 volts to the picture tube assembly.
The image intensifier tube has a photocathode that converts photons into electrons. When electrons pass through the pipe, the atoms in the pipe will release similar electrons, the number of which is the original number of electrons multiplied by a factor (about several thousand times), which can be done by using the microchannel plate (MCP) in the pipe Work. A microchannel plate is a tiny glass disk containing millions of tiny pores (microchannels) inside, fabricated using fiber optic technology. The microchannel plate is in a vacuum, and metal electrodes are installed on both sides of the disc. Each microchannel is about 45 times its width and works like an electronic amplifier. When the electrons from the photocathode strike the first electrode on the microchannel plate, the electrons are accelerated through the glass microchannel under the action of a high voltage of 5000 volts between the two electrodes. When electricity passes through the microchannel, thousands of electrons in the channel are released, a process called cascade secondary emission. In short, the original electrons hit the sides of the microchannel, and the excited atoms release more electrons. These new electrons also hit other atoms, creating a chain reaction that results in a handful of electrons entering the microchannel and thousands opening the channel. An interesting phenomenon is that the microchannels on the MCP have a slight inclination angle (about 5-8°), which is not only to induce electron collisions, but also to reduce ion feedback and direct optical feedback from the phosphor layer at the output. Night vision images are notable for their eerie green sheen.
At the end of the image intensifier tube, the son hits a phosphor-coated screen. The electrons maintain their relative positions as they pass through the microchannel, which ensures a good image because the electrons are arranged in the same way that the photons were arranged in the first place. The energy carried by these electrons causes the phosphor to reach an excited state and emit photons. These phosphors produce a green image on the screen, which has become a feature of night vision goggles. Through another pair of lenses called eyepieces, the green phosphorescent image can be observed, and the eyepiece can be used to magnify the image or adjust the focus. NVDs can be connected to electronic display devices, such as monitors, or to observe images directly through the eyepiece.
