subject: Night Sight Devices: How Do They Work? [print this page] Getting yourself an instrument with which you can see at night is exciting, but you have to dig into the technicalities first.
You will get a grasp of technical stuff like how these instruments succeed in amplifying the available light at night, get help from the infrared illuminator and displaying the images on a phosphor screen.
When you think about a product line using night vision, monoculars (and scopes) will have to be considered. Binoculars in this category are few and far between. Goggles do use night vision, but thats for kids. Well, that does not mean we will ignore this, since you might be looking at a pair for a young kid! Anyway, We will definitely only consider the basic (but good enough) level of night vision. The higher levels (another 3) are very expensive unless of course, youre willing to dig your hand deep into your pocket!
Primary object of night vision devices: Unlike binoculars, night vision devices are primarily intended to make it possible for you to see in the dark, not to magnify distant objects or see objects far away. So, how can you see in the dark? How does night vision work?
Enhancing light: Without some light at night, night vision will not work. For humans the light coming from the moon or stars (or anything else) is not enough, but for these devices this is not a problem. They all have complicated electronics by means of which this light can be magnified to such an extent that seeing in the dark is possible.
Provision of extra (infrared) (IR) light: If the light available (from moon etc.) is not enough for the amplifier to provide a bright enough image to the viewer, extra light can be provided by means of a special feature, known as the illuminator. This feature is the IR illuminator. It throws an infrared beam at the object youre trying to look at, but since its infrared, you can hardly see it (and animals cannot in any case). Then the objective lens of the scope/monocular or two objective lenses of the binocular collect this extra (infrared) light along with the available visible light and present(s) a jaw-dropping image. Sometimes the amplifier cannot deliver a good image on its own, since the available natural light is not enough to be amplified. Then you need the IR illuminator (or at least an external, supplementary one), or else you will never know what was making all that noise out there in the bush! The two feature together can give an incredible performance: You can have from 15,000 to 40,000 (in the case of the high quality devices) more light as would be without these features!
Where do you see the image? Obviously through your eyepiece, but thats not the issue. Are you seeing the object directly? No, youre not. Youre actually seeing a projected electronic image. This image, which is not chromatic, is projected onto a little screen inside the device. This screen is green since its a phosphor screen (like the monochromatic TV screens in the old days) and youre seeing the images in shades of green. An interesting fact is the fact that people can distinguish more shades of green than any other colour, so although the image is not in colour, its excellent considering its night vision.
All night sight instruments need light sensitive components and using the instrument properly will give you the maximum of 2500 hours of a lot of pleasure. You will have a very long time discovering what goes on at night when no other human can see. The wrong use, however, will harm these parts. By wrong use we mean exposing it to too much light. It might make sense to use a spotlight to see whats going on in the dark and then use your night vision device in combination with this spotlight, but this is exactly what you should not do. It is not made to deal with such a lot of light. Finall, think twice before letting someone else use your night sight device! You might end up with a severely damaged instrument!
Black spots on image area: Night vision image tubes are never flawless, and every night vision intensifier tube will have blemishes to some degree. These blemishes translate into scattered black spots on the image area. This is where price comes into the frame. Cheap devices will have more and bigger black spots than the more expensive ones. The fewer and smaller the blemishes, the better the quality and therefore the higher the price.
