Why focus both at the front (objective) and at the eye piece (eyepiece)?
The short answer is that you're not looking through a night vision device, you're actually seeing the phosphor screen at the bottom of the tube. The objective lens focuses the image in front of the intensifier tube, which converts the image into a stream of electrons, which are then reimaged at the bottom of the tube. To see a clear image, you need to focus your eye on the bottom of the intensifier tube where the image is formed. Everyone's eye vision is different, so eye focus is also very important. Focus the line of sight first, and then transfer to the objective mirror to ensure a clear image. Also, you'll need several shots of each prism to get the sharpest image.
Special design for night vision goggles?
Night vision devices are designed to be automatically shorted when not in use, and only start to work when the start switch is pressed. The binocular device has an "on/off" switch that requires the user to turn off the device after use. It is normal if there is a certain "humming" sound, it is intentionally designed to help the user distinguish between power on and power off. The image in the night vision device is formed by a phosphor screen, which has a little astigmatism, so it cannot be as clear as a daytime telescope. Tiny black spots may be seen in the image, which is a natural phenomenon caused by the process of manufacturing the intensifier tube, not a quality problem.
What are the differences between different generations of night vision products?
The main difference is the advancement of booster technology. The first generation uses an intensifier tube to enhance the brightness of the surrounding environment, which can accelerate the flow of electrons to hit the phosphor surface, just like the principle of a TV screen. Generation II devices, on the other hand, added a micro-frequency disk, which increased the number of electrons striking the phosphorous surface, thereby enhancing brightness. Gen III devices add a gallium arsenide photocathode, which produces a higher number of photoelectrons than Gen II. Both the second generation and the third generation have made great progress in increasing brightness, but their prices are relatively expensive, which discourages most customers. The quality of the first generation is good, and its brightening effect can also meet the needs of most ordinary users and many professional users, so it has a market.
