I should preface this with a disclaimer that I am a pacifist, and a civilian at that. My interest in night vision comes from camping in the wilderness. That said, the one-eyed man in the land of the blind is king.
Image Intensifier Tubes
An image intensifier amplifies the amount of light to its user, it does not project photons nor does it work in complete darkness. There is a long history of its development throughout the early 20th century. In the early days, the image intensification wasn't powerful enough to see without active infrared illumination. Active IR is still used today for extreme low-light conditions such as indoors, underground, and new moon. Photos taken by me through a PVS-14 with a Gen 3 filmless white-phosphor tube.
These devices were first used for night combat in WWII, and became more widespread in the Vietnam war. The earlier devices were barely man-portable, while later on they became miniaturized. These are most commonly head-mounted, as some devices are not rugged enough to withstand recoil from being mounted on a firearm. Mounting options range from being handheld, to helmets and lightweight "skull caps".
Being able to see in the dark is supremely useful, and especially without bringing undue attention to oneself by using a flashlight. Another advantage is that the field of view and range is superior to most visible light options. A limiting factor to their widespread use may be cost, as these analog devices start at roughly $2,000 for older generation tubes. However, there are cheaper options which are digital, and more accessible to consumers (although they don't work quite as well yet).
I find that head-mounting is the best mounting option, as it enables greater awareness without constantly having to hold something up to one's eye. It is noticeably heavy and can be uncomfortable for longer periods of time, so using a counter-weight is optimal for comfort. If you have one of these devices, DO NOT STORE WITH ALKALINE BATTERY INSIDE. Alkaline batteries will leak and corrode the battery terminals. If you're going to store them with the battery, use Lithium batteries, or anything but alkaline.
The superior aiming option is infrared laser, followed by holographic sights. Red dots are sub-optimal due to focal length issues. With an infrared laser, point shooting is possible (without shouldering the weapon). Iron sights are unusable due to focal length. Focal length is a constant issue because the objective lens is usually focused on infinite distance, it's like having farsightedness most of the time.
Thermal Imaging Cameras
A thermal imaging camera works roughly the same in principle, but it detects electromagnetic radiation in the infrared range. These work under no light conditions, as they do not rely on lighting sources at all. Photo taken by me through an N-Vision HALO device with a BAE Systems core.
Thermography is quite useful for detecting heat sources, they will stand out especially at night. Modern thermal imagers are digital devices, usually limited by the resolution of their cores and screens. They are also quite expensive, modern man-portable thermal imaging cameras can be much more costly than image intensifier tubes.
There is no diopter lens, only a LCD screen, thus the user is peering into a screen. The only aiming option is built-in and passive, since a thermal imager won't be able to detect infrared laser light.
See Without Seeing
Create ways to see without seeing
I think there's something about cameras that inherently make them esoteric. Native Americans thought that getting their picture taken, takes a part of their soul from them. I think they're right, but it's more of a "copy and paste" rather than a "cut and paste" operation. A camera that captures what Eyeball Mk. I can not see is real life magic in a way. In SCP Overlord, a cursed video camera that can see otherwise invisible threats is a major plot device. This technology which grants the ability to see the unseen, is a bit like having demonic power.
There have been a lot of unexplained phenomena captured by cameras and other imaging devices. The Shroud of Turin is a famous one where UV photography is used to capture what is purported to be the image of Christ Himself, although this is debatable. With vastly improved camera technology, it's far more likely that most supposed spirit photographs are fake, especially since a lot of older photographs relied on low image quality to be plausible.