Field of View (FOV)

Field of View refers to the angle of view as measurable from the objective of a single tube/pod

The specification is written out in degrees of angle.

Many devices (for instance PVS-14, MNV-K, individual pods of DTNVS and PVS-1431 etc) have a FOV specification of around 40 degrees (compare this with human sight which has 90 degrees central view within a total of 120-140 degrees including peripheral vision).

The exact degree of FOV is possible to calculate if one knows the diameter of a tubes input window and various physical measurements and optical properties related to the lens employed by the device.

Overcoming FOV limitations

Naturally any field of view not equal to human baseline FOV is going to limit perception and awareness for the user and call for a number of strategies and techniques to compensate for this. The most obvious weakness is the loss of not only about half of our daysight direct focal field of view but peripheral vision (proven to be especially reactive to sudden movements or environmental changes, making any night vision device arguably similar to a horses blinders. In any tactical or observational situation this is of course an immediate weakness and possible exploit.

This has led to the development of devices, accessories and lens kits that improve an individual devices FOV or by changing the devices setup by either adding tubes or making them adaptable to different conditions and situations.

Some solutions exceed the average 40 degree FOV and therefore lessen the tunnel-vision effect that users of night vision devices have to deal with in the field since observing any area that is not effectively an enclosed corridor requires constant panning around of the device and head.

Increased FOV on a device facilitates the users effort to cover any given area.

Such devices and upgrade lenses are marketed towards users looking for an improved in both awareness and ergonomy.

Panoramic devices

The FOV-limit solutions of this category rely on the physical angles at which multiple tubes are arrayed instead of optically improving the FOV of individual tubes. Compare this to ”regular” or fixed angle bridges and binocular devices: the latter two have no variable angle between pods and instead the pods or dual mounted monoculars are perfectly parallel to each other. It follows that the overlapping areas of each pods FOV creates a combined image with a lot of “wasted” view. The aim of panoramic devices is to lessen this redundancy and make better use of each tubes FOV.

Panoramic Night Vision Goggles (Quads)

An iconic and highly functional solution to the limitations inherent in any devices FOV is the panoramic quadruple tube setup. Originally designed for aviation purposes it has a quadruple array of tubes divided into two pods with two IITs each, one viewing straight ahead and the other offset to the side by a few degrees in order to achieve the smallest yet functional possible overlap of image. At the ocular end the eyebox lenses have been fused together, thus providing the user with a seamless blend of the overlapping circles. At correct interpupillary distance (IPD) setting the two parallel front facing tubes will provide a similar effect as when using a binocular device, with the added bonus of being able to either let the sideways facing tube images be observed for movement by the users peripheral vision or directly observed by glancing sideways.

The Panoramic NVG has also been further developed and ruggedized for use in dynamic environments outside of a cockpit. This latter device is known as Ground Panoramic Night Vision Goggle or GPNVG-18 and features similar solution with two pods containing two tubes each. It has been widely popularized in movies, video games and other media showing these devices in use by a number of highly elite Special Operations, Counter Terrorist and Hostage Rescue teams.

Panobridge

The panobridge is a dual monocular bridge that is engineered to widen the angle between each pod or monocular in a binocular setup, thereby increasing the compound field of view by lessening the overlap of input reaching the user.

Developed outside of government military contracts the various available iterations on this concept are products of mainly civilian enthusiasts turned producers and have garnered much interest and positive response among users of dual mono-device setups.

As of August 2022 there is no dedicated binocular housing which integrates the panobridge function, although a pano-adjustable version of the RNVG housing could hit the market in the forseeable future.

Wide-FOV solutions

This section treats solutions that affect the optical parameters that define FOV angles and lists the two main categories: devices constructed to such specifications and aftermarket components to replace optical assemblies on existing devices.

High FOV Devices

Night vision devices with higher than average FOV, such as the Fenn NG700D.

Wide-FOV optical upgrades

Manufacturers have released objective assemblies as aftermarket upgrades to compatible devices, increasing their original field by up to 10 degrees. These solutions mainly require replacing objective and ocular to function without affecting the viewable image negatively.