How night vision scope is made - material, manufacture, making?

May 5, 2021

 

How night vision scope is made - material, manufacture, making?

People were always wondering about the ability of some animals to see in the dark. Therefore, the invention of night vision devices was quite an expected thing. The first NV devices appeared in Germany right before World War II. During the war, America developed its night vision equipment. The first models were bulky and required good illumination. But gradually NV devices have become more compact and efficient in poor visibility conditions.
Today, night vision devices can be bought in a store or ordered by the Internet. These accessories are the most popular among hunters, wildlife watchers, and the military. One of the important elements in any night vision device is the scope.So let's figure it out, how night scope is made?

Materials
It needs to take good materials to make a good scope. The objective lens and output window eyepiece is made of special optic glass. The main element of the scope is the image intensifier tube, made of metal and ceramics. Inside the image intensifier tube, there is a phosphor screen, and microchannel plate, which is made of fiberglass.
After assembly, the image intensifier tube is placed in a special impact-resistant plastic cover. All elements are securely fixed and soldered. In case of impact, the plastic cover will protect the image intensifier tube from damage.

Design
The principle of work and the construction of the night vision devices are quite complex. It all starts with the objective lens. Every object reflects light, visible and invisible to our eyes. Lenses capture this light, gather it into a light beam and direct it to the photo-cathode. At this stage happens the transformation of photons into electrons. The electrons are sent to a special chamber with the microchannel plate. This plate is made of fiberglass, and it has hundreds of microtubes on its surface. The task of this element is to increase the number of electrons. The more micro-holes are on the plate, the more electrons can be obtained. The diameter of the microchannel plate in night vision devices Gen 3 is no more than 1 inch. Also, this part of IIT is very thin – about 0,4 inches.
In the last stage, electrons are bounced from the plate and hit the phosphor screen. When hitting, electrons create small flashes of light. In this way, they convey the piece of information about the surrounding objects and the screen gathers it in one picture. The result – the user sees a clear bright image.
The entire process of converting particles of light into a clear image, described above, would be impossible without a source of power. All night vision devices need good rechargeable batteries. The source of power is located roughly under the microchannel plate chamber. The powerful the optics, the more energy it requires.

The Manufacturing Process
The core element in the night vision scope is an image intensifier tube. Manufacturers use more than 400 different processes to make the main parts and assemble them in the tube. Let's take a look at the most important points of production.

Photocathode
This element is made of special glass. Usually, manufacturers buy round glass blanks from subcontractors rather than making them themselves. The round piece is covered with a layer of gallium arsenide and then heated until it starts to melt. To securely connect the two layers, the part is compressed under the press. The last step is polishing and checking for defects. Now the photo-cathode is ready.

Microchannel plate
The plate is the most difficult element, on which it depends on how well the image intensifier tube would work. For its production is used the so-called “a two-draw process”. To do this, workers take a specially prepared ingot made of glass. The ingot is placed in the furnace, or rather in its upper part. The furnace has several temperature control zones. Therefore, the temperature in each zone can be different. The ingot is gradually heated at a temperature of 500 degrees, while a large glass globule is formed in its bottom part. Globule reaches a certain size and falls, creating a thin glass thread. This thread has to be cooled quickly. The special traction machine picks the glass threads, cutters clip them to the same length and form bundles. These bundles are then twisted into hexagons. The obtained hexagons are placed back in the furnace and heated. Further, all processes are repeated from the beginning. But on the second time, the fiber hexagons are much narrower. The result of this hard and long process is a glass boule. The boule is cut into thin slices or plates, each of which is cleaned of cladding glass. After removing the cladding glass there opens hundreds of micro-holes on the surface of the plate. The final touch – the plate coats with nickel-chrome and then aluminum oxide for it can carry an electrical charge.

Phosphor screen
This is a tiny fiber disc, it is usually purchased from subcontractors. First, the disc is well bonded in a tube body and then coated with phosphor. Such material as frit is used to connect all elements. The frit melts quickly when heated and reliably holds all the parts together. After heating the disc is cooled and sprayed with the solution of water and phosphor. Then the water is evaporated, and phosphor remains on the screen, creating a thin smooth coating.

Tube body
The body is composed of several rings made of metal and ceramic. Each ring holds a specific section of the image intensifier tube. To firmly bond all the rings, manufacturers apply indium between each of them. When heated, indium melts and reliably “glues” all elements.

Assembly
After the elements of IIT are ready, they need to be accurately placed in the body. The assembly starts in a special sterile room with no dust and moisture. The workers first place the microchannel plate and battery pack. Then the body is placed in the exhaust station for removing all air. Only after that the photo-cathode and phosphor screen is put in the tube and fixed there. Assembled image intensifier tube must pass through several testing to check how it works and whether it meets the required parameters. If the testing shows good results, the tube is placed in a plastic “boot”. The boot is closed and the air is removed again. A few more tests and the image intensifier tube is ready, Now it can be placed in goggles, binoculars, and other night vision devices.

Quality Control
A good manufacturer controls the production process at every stage. Each detail is not allowed to the next stage until it meets the requirements. For better quality control special calibration equipment is used. It allows the workers to check the temperature in the furnace, the diameter, and thickness of the plate, as well as other parameters. Calibration equipment is also checked regularly for its correct work.
The final product is also thoroughly tested depending on the conditions in which it will use. If the device is designed for hunters or nature observers, it can be tested by shocking or vibrations. If for military purposes, it will be placed in conditions of high temperature or humidity for several days. Visual testing of the product work is also very important. Now you know how difficult it is for a manufacturer to produce a quality night vision device and why the cost for some models is so high. If you need a good night vision scope, buy it only from a trusted vendor.