Night vision device
Night vision device means night vision device. Whenever the name of night vision device comes, the story of some James Bond films comes to mind. With night vision device, we can see even at night. Let us know how the night vision device works at night. Night vision device works on two principles.
1. Thermal Imaging: The body temperature of any living organism is higher than the temperature of non - living object. In this technique, the heat emitted from the body of the living being is captured by a device called thermal imaging device.
2. Image enhancement: In this method, the small number of light rays coming from the object, which our eyes cannot see, are amplified by collecting them. Due to which we start seeing the object.
Infrared Light: To know the working method of night vision device, we also need to know a little about infrared light. The amount of energy in light is inversely proportional to their wavelength. That is, light of shorter wavelength has more energy and light of longer wavelength has less energy. The violet color of the light we can see has the most energy and the red color has the least energy.
The light in front of violet light is called ultraviolet or ultra violet rays. The light before the red color is called infrared or infrared rays.
Now let's know a little about the photon. As we all know, the smallest particle of every substance is an atom which is made up of electrons, protons, and neutrons. Protons and neutrons are present in the nucleus of an atom and electrons revolve around it. When electron comes from excited state to normal state, it emits some amount of energy which is called photon, it is a light particle. For example, when the heater is heated, red rays come out. It contains red light as well as infrared rays. That is, whatever object is heated, photons are emitted from it, which comes inside the infrared spectrum.
In thermal imaging, this is the emission of infrared rays is used.
How Thermal Imaging Works.
There is a special type of lens that focuses the infrared rays emitted from every object falling in the scene. Now these focused rays are scanned with an infrared detector which produces a detailed temperature pattern called a thermogram. This thermogram is encoded in a binary or analog signal. Now this signal is sent wherever it is to be seen. A signal processing unit converts this signal back into the scene so that we can see the temperature pattern. The visuals seen from this look something like this.
In the field of thermal imaging, new experiments are being done every day, which are making the scene better.
Because thermal imaging captures the heat emitted from the object, it can also be seen in full range from it. Another technique is image enhancement, which makes even very blurry reading scenes worth watching, let's know how it works.
Image Enhancement: This technique is mainly based on a device called Image Intensifier Tube.
First of all, a simple lens like in a telescope collects the light coming from the front which also contains some infrared rays. This collected light is sent to the image intensifier tube. A photocathode is attached to this tube which converts the photon particles present in the light into electrons. When this electron passes through the tube, with the help of a microchannel plate which is mounted in the tube, the number of these electrons is increased by a few thousand times. Acrochannel plate is a glass disc with millions of microscopic pores. It has metal electrodes on both sides. When the electron emanating from the photo cathode reaches the electrode on one side of the disc, the electrode accelerates this electron. When these accelerated electrons pass through the microscopic hole, they collide with the wall of the hole and excite that atom, this excited atom emits an electron. In this way, this newly created electron collides with another atom and this process continues in every hole till the end of the tube. As a result, millions of electrons come out of the channel. This electron image collides with a plate at the end of the intensifier tube which is coated with phosphorus. This screen converts electrons into photons, making the thing in front of us more clearly visible. The visuals from this device look like this. Withhis technique we cannot see in complete darkness because it magnifies the light coming from the front, if the light is zero then this technique does not work.
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