Night vision scopes are sophisticated devices used for viewing in near or complete darkness. These optico-electronic devices work by amplifying all the available light, but unlike binoculars or telescopes, night vision scopes are not intended for magnification of remote objects. A night vision scope could either be passive or active. A passive scope only amplifies the surrounding light while active scopes enhance the image electronically. However, note that active systems need to be powered, so you may require spare batteries.
How It Works
When using such a night vision scope, you will be looking at an image projected by the unit’s intensifier tube. Light enters the device through an objective lens and hits the photocathode found in front of the intensifier tube. The photocathode is responsible for producing high-energy electrons, thus creating an image on a phosphor screen on the back of the tube. The image is then projected through the eyepiece to your eye. The brightness and clarity of the image is dependent on how much light gain is produced by the tube, which could go up to 40,000 times.
Night vision scopes can be used for various reasons, which is why there are various different models. For instance, some can be upgraded with camera adapters that make it possible to capture night vision photographs or videos while other come with high power lenses to increase the scope’s observation range. Others are converted to hands-free goggles or adapted to weapon mounts, serving as nigh vision rifle scopes. Still others come with a waterproof construction that makes them suitable for marine applications.
If you are buying a night vision rifle scope, you need to consider the speed of your prey. The fast movement of animals such as deer will often smear the image in most lower-quality scopes, which would make it impossible to aim accurately. Larger objects are also easier to see, but the amount of detail (recognition range) you require should also be considered. You can also see better and further when you have sufficient ambient light. For instance, hunting on a night when the moon and start are out will be easier than on a cloudy and overcast night.
As earlier mentioned, night vision scopes are not designed for viewing remote objects, which is why they offer little magnification. However, if you need to spot targets that are far away, you would need a powerful lens. The tradeoff between magnification and field of vision should be given careful consideration since increase in magnification decreases the field of vision. When using a night vision scope to hunt at night, you will depend on it for your target acquisition plus the final targeting as opposed to the daytime, when you can use your eyes to scan and acquire targets before zeroing in on them. As such, keep in mind that target acquisition using a night scope with a small field of view can be difficult; high magnification will not make for easy acquisition of targets. It is therefore advisable to choose a night vision scope with sufficient magnification and the widest field of view available.
Night vision scopes are categorized into three generations that differ in function. First generation scopes give a clear image, but work best with a full moon. They come with an intensifier tube which accelerates electrons that strike a phosphor surface (similar to the way a television works) to amplify ambient light. Second generation scopes have an additional micro-channel plate to multiply the electrons before they hit the phosphor screen, which increases its gain. Third generation scopes, the most expensive of the three, come with a Gallium Arsenide photocathode that creates even more photoelectrons than second generation devices. Although second and third generation devices provide greater light amplification than first generation units, they are usually too expensive for most buyers.
Certain night vision scopes have a built-in infra-red illuminator that plays the role of a flashlight. This is meant to provide additional light so you can see objects even in complete darkness.
Ultimately, night vision scopes should be chosen based on the unit size, optical lens package and price that best suits you. In fact, the slight differences in technical specifications may not translate to significant differences in performance for most recreational applications.