The objective lens focuses the image in front of the intensifier tube, which converts the image into a stream of electrons and then re-images the bottom of the tube. To see a clear image, you need to focus your eye on the image at the bottom of the intensifier tube. Everyone's eye vision is different, so eye focus is also very important. First focus the line of sight, and then transfer to the objective lens to ensure a clear image. objective lens. The infrared night vision device can be equipped with objective lenses of different magnifications. The more the image is enlarged, the more light is lost, so the general objective lens is mainly doubled. Generally common lenses are doubled, tripled, or five times.