What is a Night Vision Device?
Night vision devices are electro-optical devices containing an Infra Red (IR) image intensifier tube. Many night vision devices also include IR illuminators and telescopic lenses and therefore take the form of night vision monoculars, binoculars, goggles or scopes.
So how do they work?
Most night vision monoculars or binoculars are electro-optical devices that amplify whatever existing light there is and send it onto your eyes. You actually don't look directly through the optics of a night vision binocular or other night vision device as you would on normal optical binoculars, you actually look at an amplified electronic image on a phosphor screen. The little light that there is available enters the night vision glasses through an objective lens and strikes a photo cathode. This cathode has high energy charge from the power supply which accelerates across a vacuum inside the intensifier and strikes a phosphor screen (similar to a TV screen) and is then focused. The eyepiece then magnifies the image for you to see.
Night Vision devices can 'see in the dark' when you can't because they are sensitive to a broad spectrum of light, ranging from from the visible right through to infrared, whereas human vision is confined to a small portion of the electromagnetic spectrum called visible light. Often night vision monoculars and binoculars have an illuminator that can increase the amount of light available by shining a beam of light (invisible to the human eye) at the infrared end of the spectrum, that the device can then use to 'see' in almost complete darkness.
How Digital Night Vision Works
As with a normal night vision devices, available light is collected through the objective lens. But instead of focusing this light on an intensifier and converting the energy into electrons, most digital night vision devices process and convert this optical image into an electric signal through a highly sensitive CCD (Charge-Coupled Device) image sensor, similar to what is found in most digital cameras and other imaging devices. This electrical signal is then transferred onto a micro-display, which is a type of LCD flat-panel display screen that usually takes the form of an eyepiece. Because you are converting the optical image into a digital signal, it is then relatively easy these days to take that signal and store it onto a memory card etc. So you can record what you a seeing as either an image or as a video.
Which device is best for me?
The digital devices are more robust and tend to include recording features, but traditional night vision devices can be more sensitive. The technology has improved over generations so broadly speaking 'Gen 2' will outperform 'Gen 1' and so on, but likewise that will add to cost. Whilst intensifier tubes can be more sensitive, they can also be more delicate and cannot be exposed to bright light so a little care has to be taken with these units. The brightness of the IR illuminator has the same effect as the brightness of a torch on what you are able to see, but you can buy IR torches as addition items to 'assist' your devices too. Just like coventional binoculars and monoculars the size of the objective and the magnification has an effect on the brightness, clarity and field of view. If you plan to use the device to help you walk around though less magnification is more or you'll soon be bumping into things! There are more obvious features too like waterproofing and mounting options, but if you would like further advice or to see some products in the flesh please do not hesitate to contact us.
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