Skip to main content

Ronald White

Photographic & Optical Specialists

Home
About Us
Contact Us
Site Map
Sale & Special Offers!!!!
Cameras
Second Hand Cameras
Wearable/Adventure Camera
Video Cameras
Nature Cameras
Lenses
Second Hand Lenses
Flash Guns
Second Hand Flash Guns
Camera Accessories
Film & Slide Scanners
Binoculars / Monoculars
Telescopes
S/H Binoculars/Telescopes
Night Vision
Night Vision FAQ
Projectors & Viewers
S/H Slide Proj. / Viewers
Second Hand Cine Equip.
Lamps
Film
Darkroom & Chemistry
Second Hand Darkroom
Manuals, Books & DVD's
Printers & Digital Frames
Microscopes & Accessories
Magnifiers
Roberts Radios
Studio Lighting
Photographic Services
Cine & Video Servives
WEEE (Waste Electrical)
Maidstone Zoo
Maidstone Trolleybus
Falklands DVD Special
Useful Links
 

 

 

Night Vision FAQ

 

1. How Does Night Vision Work

Every Night Vision device has four major parts:

Objective Lens
Image Intensifier Tube
Power Supply
Eye Piece


Night Vision technology works by the principal of gathering and amplifying available light of all wavelengths (visible and invisible to human eye). Light/Image is gathered by the objective lens (1) and focused on a photocathode part of the image intensifier tube (2). Photocathode, under the influence of gathered light emits electrons. The electrons are given a high-energy charge by the power supply and accelerate through the vacuum inside the image intensifier tube and strike a TV like green phosphor screen reproducing the image. The image is focused and magnified by the eyepiece. The phosphor screen is green because the human eye is more sensitive to different shades of green. Green is also the color that alleviates stress and eye fatigue.


 

2. What do terms Gen 1, Gen 2, and Gen 3 mean?

Gen. is an abbreviation for "Generation". Night Vision devices of all generations are evaluated by two commonly used measures:

Light gain: measures how many times a night vision unit can amplify the available light.
Resolution: measures how sharp and clear the amplified image will appear.
(Resolution is defined in line pairs per millimeter or lp/mm).


Gen 1 equipment was originally developed in the 1960s primarily for military applications. Gen 1 night vision equipment is build around image intensifier tubes with very simple configurations. Gen 1 image tube is vacuum-sealed and consists of a photocathode and a phosphor screen. Gen 1 equipment has lower light amplification (gain) and image quality (resolution) when compared with Gen 2 and 3, especially on the edges of the screen. Nevertheless, Gen 1 night vision is the most popular and demanded product line of night vision units on the consumer market. Gen 1 equipment is great to have fun with and satisfies the needs of most recreational demands.


Gen 2 equipment was developed through the 1980s, and differ from Gen 1 with a different tube engineering. Gen 2 equipment is enhanced by utilizing a micro-channel plate (MCP). MCP looks like a honeycomb where each cell has a large number of channels for electrons to enter. It is located between the photocathode and the phosphor screen. For each accelerated electron emitted by the photocathode it strikes the channels of the MCP, about 1000 electrons come out on the other end and hit the phosphor TV-like screen. MCP boosts light gain of an image tube by about 1000 times. As a result the output image is brighter and clearer. Gen 2 equipment is costly and fits the needs of more advanced users. It is widely used for tactical and professional surveillance purposes.

Gen 3 equipment is very similar to Gen 2 by its use of MCP, but in addition, it uses a Gallium Arsenide (GaAs) photocathode, which further enhances light sensitivity. As a result, more electrons are emitted that hit the MCP and the image screen to produce a brighter image. Gen 3 equipment is the latest in night vision technology. It is very expensive. Gen 3 equipment yields best results when used in poorly lit environments such as in canyons, forests or jungles. If most of your surveillance takes place in urban or nearby areas, Gen 2/2+ equipment will do an excellent job for you.


3. What is Infrared (IR) Illuminator and do I really need one?

Infrared Illuminator (simply IR) is a source of infrared light, which is invisible to the human eye. It can be compared to a powerful flashlight that emits infrared light instead of a visible white/yellow light. As an accessory to your night vision device, it is used to increase available light for a brighter image. Most of the IR illuminators on the consumers' market are based on LED (Light Emitting Diode) that is similar to your TV's remote control. Effective range of those units, on average, is about 60-80 feet. Since minimal focusing distance of a standard Gen 1 night vision scope or a binocular is around 30-50 feet, you will reap the benefits of an IR Illuminator only in the 50-80 feet range. The only exception to this rule is goggles. Goggles have a very small minimal focusing distance, usually 6"-9" inches, and in this case IR illuminator is a must. Since most goggles come with IR, you won't have to make any decisions there. However, beware of claims that stretch the range of conventional LED IR illuminators to hundreds of yards, not true! IR illuminators with a range of a 100 yards or more are based on powerful lasers.


4. What is the effective viewing range of a Night Vision Device?

It varies anywhere from 300 to 1500 feet. The viewing distance depends on the area, conditions and a size of your target. Overcast conditions, fog, rain and snow will significantly reduce the effective viewing range. On the other hand your viewing range will increase dramatically under clear skies and/or full moon. Light reflective surfaces such as snow or sand will also increase the effective viewing range of your night vision device. Infrared illuminator (IR) may help, especially in enclosed environments.


5. Can I use night vision in complete darkness?

Though it is true that night vision devices require little light, it is possible to use them in complete darkness with help of an IR Illuminator. Since most of the time you encounter complete darkness in enclosed environments, high magnification power is not a necessity, you'd rather be able to see at a very close range. In this case the most effective viewing device are goggles. Most goggles have magnification power of 1, built-in IR Illuminator, close focus and a viewing range of a few hundred feet. 


6. Can a Night Vision device and/or Infrared Illuminator be harmful?

Night Vision technology is absolutely harmless. It does not emit any type of radiation nor will it blind you if a bright light hits it while in use. Most likely it will damage the device. Night vision is no more dangerous or harmful than watching TV. Diode (LED) based IR Illuminators are also harmless. Laser based illuminators on the other hand, CAN be harmful to your eyes. If you have a laser based IR use it with caution. Laser based IRs seldom appear on the consumer market.


7. Night Vision DON'Ts (precautions)

- Not turn your unit on in day light
- Do Not aim your unit at bright light (even in the dark)
- Do Not attempt to disassemble the unit
- Do Not drop or shake the unit
- Do Not touch the objective lens (touch it only with soft non-abrasive cloth)
- Do Not store the unit without a case
- Do Not use the unit for other uses than recreation


8. How Do I Focus My Night Vision Unit?

If you have a regular scope:
The unit must have an objective lens and eyepiece adjustment. First, adjust the objective lens to perfect the image. Then adjust the eyepiece to your eyesight.


If you have binoculars or goggles:
You must adjust each eyepiece separately. To do this close your left eye and make necessary adjustments to the right eyepiece. Then open you left eye and make adjustment to the left eyepiece to get a full contrast image. Some night vision goggles require objective focusing first, and then adjusting the eyepieces. Don't forget that all night vision devices have a minimal focusing distance, a minimal distance at which objects can appear in full focus.