Electrophysics offers a complete line of high-performance infrared cameras, thermal imaging and night vision cameras. Our products include: image intensifier, IR thermal imaging, low light products and more.
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Image Intensifier Tutorial

Image intensifiers are sophisticated electro-optical devices that amplify low-light images. They have been popularized primarily by their use in night vision applications (both military and commercial). If you have seen the familiar green tint images in movies and television news coverage, you are seeing the output of an image intensifier being photographed or video-taped.
 
How Does an Image Intensifier Work?

The task of amplifying low light signals is not a simple one. As such, to make an image intensifier requires a complex manufacturing process involving over 400 separate steps. However, their function is quite straight-forward. In order to amplify low-light images, image intensifiers first convert light particles (photons) to electrons, perform amplification of these electrons, then convert back to photons, as shown below.
 
 
The very dim light reflected by scenes at night (lower than 0.1 lux) is focused by an objective lens onto a highly sensitive photocathode. This dim light consists of energy in both the visible and near-infrared portions of the electromagnetic spectrum. When the light impinges on the photocathode, the light sensitive portion of the image intensifier, electrons are emitted with amplitude determined by the photocathode's spectral responsivity and the amount of light energy. Because of the image intensifier's internal electrical field, these electrons are accelerated toward the microchannel plate assembly, the image intensifier's amplification mechanism. The microchannel plate is a glass plate with millions of tiny closely-spaced channels bored through it. The plate is coated with a special substance that produces secondary electron emission when impinged by an electron. Due to the potential difference across the plate, an incident electron enters a channel and frees other electrons from the channel wall. These electrons are accelerated along the channel in turn striking the channel surface again and again, giving rise to more and more electrons. Eventually this cascade process yields a cloud of several thousand electrons which emerge from the rear of the plate. Electrons exiting the microchannel plate strike a phosphor that emits light proportional to the amount of electrons hitting it. The image is green because the selected phosphor glows green when charged. The green color is selected because the human eye can differentiate more shades of green than any other color. Because the image is inverted, a fiber optic "twister" is used to rotate the image 180°. A special relay optic focuses the image properly to match the image plane requirements of video and 35mm SLR cameras.
 
Simplified View

Gen 1 –These are the first so-called night-vision devices and were introduced in the early 1960s and first fielded in Vietnam. These devices utilized a multi-alkali S-25 photocathode having a spectral response extending from visible to about 850nm. In order to have sufficient sensitivity for use in night vision applications, three Gen 1 image intensifier tubes needed to be cascaded, each producing some gain. The result, though highly sensitive, suffered from significant edge distortion as well as poor life expectancy (less than 1000 hours).

Gen 2 –By the 1970s, the microchannel plate was introduced that delivered high sensitivity imaging without the need to cascade three stages.As a result, night vision pocketscopes and night vision goggles emerged as viable products with improved operation life (2000-4000 hours).

Gen 2+ – More recently, improved Gen 2 devices have been developed (known as "SuperGen") that deliver improved sensitivity and improved lifetime (10,000 hours).

Gen 3 – By the late 1980s, image intensifiers became available with photocathodes made from gallium arsenide. This produced significantly more sensitivity and an extended near-infrared spectral responsivity range to 950nm. An internal ion barrier coating was developed to increase the lifetime to 10,000 hours.

Gen 3 FilmLess – Introduced in 2001, thin film image intensifiers incorporate a new manufacturing technique, which have made it possible to reduce the thickness of the ion barrier film and increase further the unit's sensitivity, improve signal-to-noise and contrast performance and reduce blooming due to viewing bright sources.
Advantages of Image Intensifiers

  • High resolution
  • Ability to identify people
  • Low power
  • Low cost
  • Adaptable to standard video and photography cameras and lenses
Advantages of Thermal Imaging

  • Very high contrast (typically)
  • Very good at detecting of persons and vehicles
  • Not effected by bright light sources – no blooming
  • Works in total darkness
 
 
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