Image intensifiers are integrated with low light cameras in order to increase the camera's ability to operate in the presence of ambient light sources. The tools consist of a vacuum tube and intensify the image by adding electrons in a proportionate manner during the conversion of photons to electrons. The electrons are added with the help of a microchannel plate.

Conventional instrument models provide support in the imaging of X-rays, gamma rays, and infrared light. They are found in many devices such as night vision goggles.

Types of Image Intensifiers

Image intensifiers are divided into three primary product categories:

Gen I: The optoelectronic mechanism was designed in the early 1960s and achieved maximum signal gains of 150 dB by relying on of electrostatic focusing and electron acceleration. They pick up light sources as low as 0.01 lux. However, the systems had problems, including distortion, short-lived components, and massive dimensions and are no longer in use.

Gen II and Super-Gen II: This classification represents the most prominent products for integration with ICCD cameras. They were one of the first components featuring microchannel plates. The efficiency of the elements is lower compared to Gen I due to the loss of some electrons coming into contact with the plate. However, the equipment produces enhanced resolution images and is easy to handle given their compact dimensions. Furthermore, they do not give rise to image distortion. The systems pick up light sources as dim as 0.001 lux. Super-Gen II employs photocathodes with extended spectral ranges.

Gen III and Gen III filmless: They deploy the same technology as the Gen II versions, with the addition of gallium arsenide as a coating for the photocathode. The plates incorporated in such tools possess superior resolution. Moreover, they feature ion-barrier films. The instruments identify light as dim as 0.00001 lux. In recent days, higher resolution tubes have been added to the product line.

Operation

The optoelectronic devices operate by changing photons from a dim light source into electrons. These elements are then enhanced and converted back into photons. The particles emitted from the light output pass through an objective lens. Here, they are concentrated onto a photocathode and displayed as an image. As the photons come into contact with the cathode, the unit emits electrons using the photoelectric effect.

The electrons are sped up via a high voltage potential forcing them to enter a tilted microchannel plate. One of the electrons hitting the plate results in the emission of several analogous particles. The tilt facilitates the release of more particles. This process is known as secondary cascaded emission.

Due to the high voltage difference across the plates, the electrons are transmitted in a straight line. A lower charge differential accelerates the speed of the particles. They collide with a phosphor screen. Each electron converts into a photon and creates an image. An eyepiece lens is employed to focus the image.

Applications

Image intensifiers detect and amplify images of limited brightness to form sharp images of high contrast. The technology is deployed in several fields, including:

• Astronomy
• Rapid imaging
• Photon counting
• Fluorescence lifetime measurement
• Plasma display panel (PDP) emission

Features

The apparatus supports numerous features. Some of the common attributes include:

• Photocathode: This acts as the medium at the point where photons are transformed into electrons. The coating on the component stimulates the conversion. Some light particles do not interact with this section and are then lost. Most recent cathodes engage gallium arsenide as the coating substance.
• Microchannel plate: This part comprises of glass that possess nominal conductivity. The elements incorporate numerous parallel channels that intersect. A microchannel plate comprises a secondary electron emitter present on the inner side. Electrons hitting the walls of the plate lead to the formation of more such particles.
• Phosphor screen: Negatively charged particles striking the screen are transformed back into light photons. Emission from these components produces a green light. The units are manufactured using materials such as gadolinium, lanthanum, and yttrium.

Image credit:

PHOTONIS Technologies SAS