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Self-Defense Weapons: Traditional and Modern

Chapter Twenty-Five
Night Vision

 Copyright © February 20, 2024 by Robert Wayne Atkins, P.E.
All Rights Reserved.

The following information is Chapter Twenty-Five in my book: Self-Defense Weapons: Traditional and Modern.

Introduction

Night vision refers to the ability to see in low-light situations. For night vision to exist there must be a minimum amount of light and the light must be within a spectral range that can be seen.

People and animals have natural night vision. But people have inferior night vision compared to animals for two reasons.
  1. The human eye has a smaller pupil compared to an animal and our pupil allows less light into the eye. Even though a human pupil will gradually become wider in low light, it does not become wide enough to significantly enhance our night vision.

  2. The human eye does not reflect light from the rear of the eye back through the retina to provide more light for visual perception. God intentionally made humans so we would work during the day when it is light and sleep during the night when it is dark. On the other hand, God made animals so they could rest or sleep during the day and become active at night.

Night Vision Technology

Fortunately humans are smarter than animals and we have developed night vision devices (NVD) that can enhance our ability to see in the dark. Night vision devices are based on one of the following three technologies.
  1. Image Intensification: It captures and intensifies the natural light that is received from some source, such as moonlight or starlight, and the image is transmitted to a special screen where it can be seen by the human eye. Usually the light of a half-moon is the minimum amount of light required.

  2. Active illumination: Hot objects such as people, animals, cars, and equipment generate some heat in the form of infrared (IR) radiation. This type of NVD uses image intensification plus illumination from the infrared band and it displays the composite image on a monochrome screen that can be seen by the human eye. Because infrared light is included, the resulting image has a better resolution than an image without infrared support.

  3. Thermal Imaging: It does not require a source of illumination and it can generate an image in total darkness. It can also create an image through light rain, light fog, and thin smoke. However, it cannot see through walls, glass, or acrylic. It detects the temperature differences between different objects, similar to the vision of a snake, and it displays the resulting image on a special screen.

Night Vision Abbreviations

The most common abbreviations are as follows: night vision devices (NVDs), night vision goggles (NVGs), and night observation devices (NODs).

Types of Night Vision Devices

Night vision devices include monoculars, binoculars, goggles, and scopes. The device will have a large diameter objective lens to allow more light to enter the device. Then the image is transmitted to a screen that can be seen by the human eye.

A NVD can be a useful tool for some hunters and for self-defense depending on each person's actual situation.

Night Vision Generations

The primary difference between the different generations of night vision devices is the technology used to intensify light. Each of the following technologies turns light into electricity and then it turns the electricity into a visual image.

When light is converted into electrons it is not possible to retain the colors of light and therefore the final image will appear in green or in white. The human eye can see green better than other colors so most NVG displays are green.
  1. Generation 1 (Gen 1): An intensifier amplifies and accelerates light electrons and focuses them onto a phosphor surface for viewing. It does create a “halo” effect around any nearby light sources. This technology is affordable and it is a very reasonable choice for most hunting and self-defense applications. Most Gen 1 devices can display a reasonable image of an object up to a maximum distance of about 100 yards (91 meters) depending on the ambient light available. However it provides the best images at 50 yards (46 meters) or less. Most new Gen 1 devices will work for about 8 hours, continuous use, before you will need to replace the batteries. Gen 1 NVD are not currently being manufactured but they may be available as military surplus. But don't buy a used one.

  2. Generation 2 (Gen 2): Enhances the Gen 1 technology by adding a microchannel plate which intensifies, amplifies, accelerates, and multiples the number of electrons, and then focuses the electrons onto a phosphor surface to provide a better image. It has a maximum rage of about 200 yards (183 meters). It has an average live expectancy of between 2,500 to 5,000 hours of continuous use. It cost almost as much as a Gen 3 NVD.

  3. Generation 3 (Gen 3): Enhances the Gen 2 technology by adding a gallium arsenide photocathode to significantly multiply the number of electrons and then focuses them onto a phosphor surface to provide an improved image. It has a maximum range of about 300 yards (274 meters) or more. It has an average life expectancy of 10,000 or more hours of continuous use. It can be used during the day without damaging the NVD but it does not enhance the clarity of an image during the day.

  4. Generation 4 (Gen 4): Omits the ion barrier film and the gating system and this increases its range and the resolution of the final image. As of February 2024 Gen 4 technology is still in the testing phase.

  5. Digital Night Vision: Enhances the Gen 1 technology but it displays the image on silicon chips. The clarity of the image is somewhere between a Gen 1 and a Gen 2 NVD. However, as of February of 2024 there is a 1 to 2 second delay before the image is displayed on the silicon chips which means that these digital devices may not be an effective targeting tool if the target is moving. It can be used during the day without damaging the NVD but it does not enhance the clarity of an image during the day.

Analog versus Digital

Gen 1 to Gen 4 NVDs are all analog devices. An analog device does not have a delay between when the image is received and when the image is displayed. Therefore Gen 1 to Gen 4 NVDs could be effective targeting tools. Only option 5 is a digital device and it has a 1 to 2 second delay between image receipt and image display.

Green Phosphor or White Phosphor

Modern NVDs are available that display the image on a green phosphor surface or on a white phosphor surface. The technology is the same and the quality of the final image is the same and the only difference is the color of the final image.

If used for an extended period of time a white image is less fatiguing on the eyes. But a white image will usually require a little time for your eyes to adjust to the normal light that is available.

On the other hand, a green image will preserve your normal night vision if you need to stop using your NVD.

Auto-Gating

Auto-gating prevents a sudden burst of light from harming the sensors in a NVD. Auto-gating is an enhancement that is worth the extra expense.

Handheld, Head Mounted, and Weapon Mounted

  1. Handheld: A handheld NVD is primarily used for surveillance or reconnaissance. If you temporarily need a handheld NVD then you could detach a NVD from your headgear or weapon and carry it in your hand until you reattach it to your headgear or weapon.

  2. Head Mounted: A NVD that is mounted on a helmet or other headgear allows you to use both hands for other tasks. It also allows you to see in whatever direction that you turn your head. However, head mounts have 3 disadvantages:
      a. When the NVD is placed in front of your eyes then its weight will put a strain on your neck muscles the longer you wear it.
      b. The NVD will reduce your peripheral vision. Your normal field of vision is about 114 degrees but a NVD will reduce it to about 40 degrees.
      c. It will be more challenging to aim your weapon unless you can easily flip your NVD up and out of the way.

  3. Weapon Mounted: A NVD that is mounted on your weapon allows you to use both hands for other tasks. It also allows you to see in whatever direction you point your weapon. This may be a clip-on device that is attached to the front of your scope, or it may be a special night vision scope. However, this reduces what you can see to the image visible through your scope. In other words, you will need to remain stationary and you can't walk around. When you fire your weapon the muzzle flash may temporarily blind you if you do not close your eyes. And the muzzle flash may damage the sensors in your NVD if it does not have auto-gating. If possible, attach a flash hider to your weapon. If it is legal in your area, attach a suppressor to your weapon.

Life Expectancy and a Used NVD

The average life expectancy of a Gen 1 NVD is usually between 1,500 to 2,000 hours of continuous use. The average life expectancy of a Gen 2 NVD is between 2,500 to 5,000 hours of continuous use. The average life expectancy of a Gen 3 NVD is about 10,000 or more hours.

The average person will use a NVD for less than 100 hours per year and therefore the average NVD will last for 15 or more years before the phosphor screen begins to wears out.

However, since it is not possible to determine how long a “used” NVD has actually been used, you should not purchase a used NVD because it may be very near the end of its useful life.

Limitations of Night Vision Devices

The amount of ambient light available and the distance to the object have a significant impact on the quality of the image that is displayed. If the minimum amount of light is not present, or if the distance to the object is too great, then the image that is displayed may not be recognizable.

However, a NVD that uses infrared will enhance the ambient light that is available but it cannot compensate for the distance to the object. A NVD that uses infrared should never be aimed directly at the eyes of a person or an animal.

A Gen 1 and a Gen 2 NVD should never be used during the day because the excessive amount of light can overpower and damage its sensors. If a bright light is suddenly turned on at night then the light could damage the sensors in a Gen 1 or Gen 2 NVD. And if the light is bright enough then it could affect your vision temporarily or permanently.

A NVD should not be used in the rain or in an environment with extremely high humidity. If your NVD gets wet or damp then dry it off as soon as possible with a soft dry towel.

Most NVDs will have a few tiny permanent black spots on the phosphor screen. This is normal and the size of the spots will not increase with use. However if several spots are in the center of the display image then they will be more difficult to ignore.

Hunting and Self-Defense Applications

The most productive hunting times are early morning and late evening when there is very little light.

Most criminals prefer to attack at night because darkness gives them the advantage of a surprise attack and it helps to conceal their position.

Therefore a NVD would be a reasonable option for hunting and for self-defense and the same NVD could be used for both applications.

Legal Issues

In February of 2024 I am not aware of any laws in the USA that limit the ownership or use of a NVD. However, laws are constantly changing and you should verify the laws in your area before you purchase and use a NVD.


Click here to read more information about the book: "Self-Defense Weapons: Traditional and Modern."

Grandpappy's e-mail address is: RobertWayneAtkins@hotmail.com

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