What is an image amplifier tube

Dictionary

ABC - Automatic Brightness Control
Protection against damage to the microchannel plate and to optimize the brightness by means of an electronic voltage control. When a bright light source appears in the picture, it can be observed that the whole picture becomes darker, i.e. turned down, this light source disappears, the picture becomes brighter again. (Usually available from Gen II upwards)

Auto-Gated (automatically regulated / clocked)

the development of clocked power supplies and ever thinner metal oxide layers on the MCP enabled the move to automatically clocked (auto-gated) tubes. With XR-5 tubes from Photonis, this technology is installed as standard and thus enables use in changing light conditions up to daylight.

Resolution (lp / mm)

states how detailed a night vision device can create and display an image. The resolution of a tube remains the same over its service life and is specified in lp / mm (maximum number of line pairs per millimeter), which can be distinguished when a standardized black and white stripe pattern is viewed with the night vision device.

Image converter tube or intensifier tube (night vision devices)

The part of a night vision device that amplifies the remaining light many times over and thus provides a usable image of the surroundings. (See also generation 1, 2 and 3)

Binocular night vision device

Night vision device with one or two lenses and two eyepieces.

Blooming

strong incidence of light is very blinding for a short time and makes observation impossible. This effect typically occurs with tubes of the first generation; from the second generation onwards, this effect is avoided by means of Automatic Brightness Control or Bright Source Protection.

Bright Source Protection (fade protection / light protection)

To protect the image intensifier tube from light sources that are too bright (daylight or spotlights), an electronic voltage control is connected to the photocathode. This significantly extends the life of the tube. Unfortunately, this “security” cannot guarantee 100% protection, so direct incidence of daylight or strong light sources must be avoided.

CCD and CMOS

two types of sensors that are used to capture images in digital night vision devices or digital cameras.

Digital image sensor

Silicone chip with millions of tiny light-sensitive diodes that convert incident light into electronic signals.

Diopter correction / diopter compensation

Possibility to adapt the night vision device to your personal visual acuity.

Distortion

There are three types of distortion. The classic distortion (fish-eye effect) mostly occurs with tubes of the first generation, as a result of which straight lines are "bent" outwards or inwards. The optical fiber distortion, divided into S-distortion and scissor-like distortion, can hardly be determined by the user and therefore cannot be explained in more detail.

EBI (Equivalent Background Illumination)
the amount of light that is emitted by the tube when there is no light from the surroundings and can be amplified (“zero value”). The EBI usually increases with the ambient temperature. The measured amount of light is given in lumens per cm². The lower this value, the smaller the amount of light that can be made visible. Thus, a small EBI speaks for a good tube.

FPN - Fixed Pattern Noise (constant interference radiation)
is a cosmetic defect that can be observed in all GEN II and GEN III tubes. With a high incidence of light, a hexagonal pattern can then be determined in the entire visible area. This is why this defect is also called a honeycomb.

Photocathode

In this component the photons (light) are converted into electrons (electric current). These are then amplified / increased in the image converter.

Gain (light amplification)

is called the factor by which the incident light is amplified. This can be specified as a tube gain or as a system gain. Tube amplification = light output (fQ) through light input (fc). System gain = light input (lc) through light output (fQ). This light amplification is, however, reduced by various filters or lenses.

Gallium arsenite (GaAs)

chemical compound used to manufacture GEN 3 tubes. Tubes with gallium arsenite are characterized by a very high sensitivity in the spectral range from 450nm to 950nm.

Generations (GEN)

Image intensifier tubes are divided into different generations. Unfortunately, the classification cannot be generalized, as there can be very large differences within the generations. For this reason, there are additional fine-tuning. The best-known tubes currently on the market are Generation 1, 2, 2+, 3 as well as Supergen, Hypergen, XD-4 and XR-5 from European production.

Generation 1 tubes / devices
The development took place in the mid-1950s.
Devices with these tubes (GEN I) are currently very widespread and probably the most widely used of all tube types. The remaining light is amplified a few thousand times, so that you get a passable picture in the dark. The devices offer a very good price / performance ratio. The edge of the image may be out of focus.

Generation 2 tubes / devices
These tubes were developed in the mid-1960s.
Tubes of this generation (GEN II) are mainly used by the military, police or authorities. Since these tubes are around 1000-2000 euros more expensive than devices with tubes of the first generation. The main difference lies in one component, the micro-channel plate (MCP). This acts as an electron amplifier and sits directly behind the photocathode. So it is possible for these tubes to amplify the light many times more than tubes of the 1st generation. Thus, the picture is not only brighter but also a lot sharper.

  • Photo-cathode: multi-alkali
  • Resolution of 40-45 lp / mm
  • Signal-to-noise ratio of 14-18
  • Service life approx. 2,000 hours

Generation 2+ / tube devices
These tubes are a further development of Generation 2. The development took place in the 1970s.

  • Photo-cathode: multi-alkali
  • Resolution of 40-48 lp / mm
  • Signal to noise ratio of 14-20
  • Service life approx. 2,000 hours

Generation 3 tubes / devices
This type of tube was developed in the USA in the mid-1980s. This generation uses a new photocathode based on a gallium / arsenite layer. As a result, the brightness and sharpness could be increased again compared to tubes of the second generation. In addition, an ion barrier was integrated to extend the service life of these tubes. With tubes of the third generation you get an optimal picture of dark surroundings. Generation 3 tubes are subject to a strict export license in the USA. As a rule, they are only delivered to the authorities of friendly (NATO) countries.

  • Photo cathode: gallium / arsenite
  • Average resolution 64 lp / mm
  • Signal-to-noise ratio average 26
  • Lifespan approx. 10,000 hours

In Western Europe, own types of tubes have been developed since 1965. Current tubes such as Hypergen, XD-4 and XR-5 are comparable or even superior to the latest American Gen 3 tubes.
The Hypergen has, for example, the following parameters:

  • Average resolution 68 lp / mm
  • Service life approx. 15,000 hours

Infrared brighteners / IR brighteners / IR emitters / IR lamps
Allows you to see in complete darkness with a night vision device. Comparable to a flashlight, but the light it emits can only be made visible with a night vision device. The beam of light from an IR radiator cannot be seen with the naked eye

Laser distance measuring device
is a device that can measure a distance to a distant object with the help of invisible laser beams. Rays are emitted and reflected on the target object. Then a factor is formed from the time required for this route and how far the destination is away is automatically calculated.

Light amplification

see “Gain”

Photosensitivity

see "Photocathode sensitivity"

lp / mm

see "Resolution"

Monocular night vision device

Night vision device with a lens and an eyepiece.

Night sights / night rifle scope

In these devices, a residual light amplifier is integrated into the telescopic sight. When looking through the riflescope you will now see an illuminated reticle with an image of the target area brightened by the built-in residual light amplifier. If the remaining light is not sufficient, an IR brightener can be used. In Germany and Austria, the possession of such devices is already a criminal offense. These are so-called “prohibited items” according to the Weapons Act.

lens

A lens that collects the light from the environment and then images an image on a digital image sensor or on an image converter tube. The lower the F-number (e.g. F1 / 1.2), the more light penetrates through the lens and the image becomes brighter. Lenses are available with different magnifications.

Lens conversion night vision device

Also known as a lens booster or ballast, it is a night aiming aid that can be attached to the lens of a riflescope from the front. The ambient light is thus amplified by the night vision device and the image from the night vision device can be viewed through normal daylight optics. In Germany and Austria, owning such devices is already a criminal offense. These are so-called “prohibited items” according to the Weapons Act. Since 2013, only attachments for binoculars, spotting scopes, cameras etc. have been allowed in Germany.

eyepiece

The side of the optics facing your eye, e.g. of a riflescope.

Eyepiece attachment night vision device

Also known as an eyepiece booster or secondary device, it is a night aiming aid that can be attached to the eyepiece of a rifle scope from behind. Thus, the image including the reticle, which is generated by the daylight optics (telescopic sight), is amplified by the night vision device. In Germany and Austria, owning such devices is already a criminal offense. These are so-called “prohibited items” according to the Weapons Act.

Eyepiece adjustment
Possibility to adapt the night vision device to your personal visual acuity.

onyx
An image intensifier tube with white phosphorus. In contrast to the usual types of green phosphorus, it creates a black and white image. This is perceived by the majority of viewers as more pleasant and realistic than the otherwise widespread greenish image.

Optical coating

a coating of a glass surface enables the loss of light to be minimized. Different layers are applied, some of which shift the wavelength of the penetrating light into the visible wavelength range.

Phosphor screen

The phosphor screen is located on the back of the image converter tube, where it shows an image of the night that is visible to the human eye. Usually the picture is in green color, as this is the most comfortable to the human eye and the most shades of color can be distinguished.

Photocathode Sensitivity
At the photocathode, light is converted into electrons; the measure for this is given in microamps per lumen. With this value, tubes can be compared values, but the other values ​​such as signal / noise ratio must not be disregarded. To determine this value, the image intensifier tube is irradiated with a light source at a light temperature of 2856 Kelvon and the sensitivity is measured.

Photonis
PHOTONIS is one of the world's leading companies in the development and manufacture of state-of-the-art image intensifier tubes for military, government, aerospace and other commercial applications. PHOTONIS products are in all NATO countries and are also used worldwide.

Projection solution for foreign hunting
With this variant of a night target solution, an IR lamp is attached to the rear of the telescopic sight. As soon as this lamp is switched on, it projects the telescopic sight's reticle onto the target. This is comparable to a slide projector: The bar lines on the rifle scope correspond to the slide and the IR lamp to the slide projector lamp. The projected reticle is not visible to the naked eye. A night vision device is required to make it visible. This should, for example, be equipped with a 5x magnifying lens. The night vision device to be used is attached to the telescopic sight by a bracket parallel to the axis of the soul. Now you look into the night vision device, offset only a few centimeters to the side, and see the projected reticle directly on the target.

A good projection solution is characterized by the following properties:
- An exceptionally sharp and bright image up to approx. 300 m.
- The weapon is attacked as normal. You don't need to worry about a “black eye” and you don't need a butt plate.
- The optimal distance from the eyepiece to the eye of 8 to 10 cm is maintained.
- The assembly can be done in a few seconds on almost any rifle scope.
- The point of impact does not change.
- Sighting in is not necessary.

The projection solution is the best and most effective night vision solution for foreign hunting. With a good combination of devices, very large ranges are possible even in poor lighting conditions.
The use of such devices is prohibited in Germany and Austria!

Black spots

These are cosmetic defects or dust particles in the image intensifier or between the lenses. Black dots do not affect the performance or reliability of the device in the slightest and are inevitable in production. Image intensifiers with obvious cosmetic defects are usually cheaper.

Signal-to-Noise Ratio (S / N - SNR)

This is the name given to the ratio of amplified signals to image noise. The signal must be stronger than the noise, otherwise the signal “disappears” in the noise. The ratio changes with the ambient brightness, since the noise is a constant value and the signals become stronger with increasing brightness. The higher the S / N value, the darker the viewed environment and the better the image.