Are you curious about how night vision devices let you see objects in the dark? Night vision devices are devices that use physical and electronic technology to amplify weak light, and they can let you see a green or black and white image. The working principle of night vision devices is actually not complicated, they are mainly composed of the following parts:
Objective lens: This is the front end of the night vision device, its function is to collect the weak light in the environment, such as moonlight or starlight, and focus it on a small point. The size and shape of the objective lens determine the field of view and magnification of the night vision device.
Photoelectric converter: This is the core of the night vision device, its function is to convert the collected weak light into an electronic signal, and amplify it by hundreds or thousands of times. The type and quality of the photoelectric converter determine the performance and generation of the night vision device.
Fluorescent screen: This is the back end of the night vision device, its function is to convert the amplified electronic signal back into visible light, and display it on a small screen. The color and brightness of the fluorescent screen determine the image quality and mode of the night vision device.
The evolution of night vision devices has led to diverse types and working modes of photoelectric converters, tailored to different generations. Here are some notable photoelectric converters that stand out:
Photomultiplier Tube: This vacuum tube-based photoelectric converter revolutionized first-generation night vision devices. It comprises a cathode, an anode, and a series of metal plates known as dynodes. As weak light penetrates the objective lens and strikes the cathode, it triggers the release of electrons. These electrons, upon acceleration, collide with the first dynode, initiating a cascade effect. Each subsequent collision with the dynodes multiplies the electron count, culminating in a significant amplification. The final electrons are collected at the anode, generating a powerful electronic signal that transforms the faintest of lights into a visible image. This technology remains a cornerstone in night vision technology, delivering unprecedented clarity and sensitivity.
Microchannel Plate: This innovative photoelectric converter, a key component in second-generation night vision devices, revolutionizes low-light imaging. Composed of a thin glass plate etched with millions of microscopic holes, it transforms weak light into an electronic signal. As light from the objective lens penetrates the holes, it triggers the release of electrons. These electrons, upon acceleration, collide with the hole walls, multiplying their numbers exponentially. The result is an output of thousands or tens of thousands of times more electrons, collected on a metal plate and transformed into an amplified electronic signal. This technology significantly enhances the sensitivity and clarity of night vision devices, pushing the boundaries of low-light imaging.
Low-Light Enhancer: The low-light enhancer, a semiconductor-based photoelectric converter, is the heart of third- and fourth-generation night vision devices. Its core lies in a layered structure known as a photocathode. When weak light, captured by the objective lens, strikes the photocathode, it triggers the release of electrons. These electrons are then accelerated and passed through an electron converter (ECC), a sophisticated device that converts electrons into photons of various wavelengths, amplifying them by tens or even hundreds of thousands of times. The resulting photons are collected by a photodiode, transforming them into an amplified electronic signal. This advanced technology delivers unparalleled performance in low-light conditions, enabling night vision devices to capture crisp, clear images even in the dead of night.
