The main specifications of any traditional Night Vision equipment are determined by the Intensifier Tube of the device. International terminology classify the Intensifier Tubes as Generation-I, II, III, with intermediate levels of Generation indicated for example as as CF-Super and Super Gen1+ etc.
This intermediary nomenclature refers to improvements over the standard tubes by such means as fibre optic plates (not an MCP) on the front or rear of the tube which improves resolution and reduces the geometric distortion that hinder standard Gen 1 tubes and thus give a better edge-to-edge definition.
Gen 1 night vision is the most popular among the general consumer due to its relative low cost and affordability. These devices typically employ a S10 or S20 photocathode giving a sensitivity of 120-200 microamperes per lumen, use electrostatic inversion and electron acceleration to achieve a gain of about 100-500x. Resolution at the center is rated at between 25-30lp/mm.
Gen 1 devices are susceptible to geometric distortion causing a blurry peripheral image. A high pitched whine may be heard during operation due a generally high power requirement. When switched off the tube may hold a charge and still provide an image without power which gradually fades.
It is commonplace for cosmetic spots or patches to be found in intensifier tubes these are customary to the manufacturing process and are to be considered normal.
MTTF (mean time to failure) 1000hrs typical
The majority of budget Gen 1 intensifier tubes are manufactured in Russia/Belarus - they account for approx 95% of the world market.
A Gen2 tube differs from generation-I and I+ by employing a S-25 (extended red) photocathode �having an increased sensitivity of 240-350 microamperes per lumen and use a special electron amplifier � the Micro Channel Plate (MCP) and will achieve around double the gain of Gen1 tubes. Resolution at the center is rated at between 28-32lp/mm.
Gen 2 tubes provide good performance in low light and are much less susceptible to distortion making them a better choice (over Gen1) for night vision photography or video capture.
They will have automatic gain control and flash protection and as such more tolerant of urban lighting than Gen3 systems
MTTF 2000hrs typical.
Gen 2+ offers an enhanced photocathode sensitivity of upto 450uA/lm. SuperGen sees further enhancements in sensitivity reaching 600uA/lm and an MTTF of 10,000hrs, whereas the furthest development of the Gen2 tube, HyperGen can achieve a sensitivity of 800+uA/lm MTTF 15,000hrs and offers greater versatility with the option of auto-gating technology which improves the capabilities of the device in rapidly changing lighting conditions.
With the use of Gallium arsenide (GaAs) for the photocathode and an MCP for gain these devices produce brighter and sharper image over 2nd generation.
Gen 3 tubes offer a virtually distortion free image with a center resolution of 45-64 lp/mm and provide the user with good to excellent low light performance. MTTF rated at 10-15,000hrs.
Such tubes are utilized by the military/government and any country producing Gen 3 intensifier tubes strictly control the availability of these systems.
Digital Night Vision
Rather than image intensifier tubes used in traditional NV devices, Digital Night Vision utilises a CCD (charge-coupled device) sensor such as are used in digital cameras.
The CCD is optimised for sensitivity within the IR spectrum and displays its image on and LCD screen again much like a digital camera. These systems can obtain a resolution around 40lp/mm.
The major advantage of Digital devices is that the CCD is unaffected by normal bright light exposure.