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Night vision basis

How to buy a nightvision equipment
(some recommendations to the customer)

The task of choosing a high quality night vision unit that satisfies your requirements
and budget is never easy. Stores and catalogues offer several types of night vision units
 made by different manufacturers. Simple reading of the registration certificates may not
 give sufficient understanding of the available selection because sometimes manufactures
exaggerate real specifications of the equipment (sometimes in 5–100 times) and aggressively
 advertise their product without a clear explanation of all technical data to the customer.

Not claming the completeness of this article, we hope that it will help you to choose a
nightvision device of the most suitable type.

Every nightvision device (NV) works on the principle of multiplying the brightness of
 the image in the wavelength of visible and near-visible infrared light. The unit contains
an objective lens, light amplification tube with the high voltage power supply, and the eye -glass.
Light (starlight for example) reflects from the object to be viewed, passes though the objective
lens and creates an image on the photo cathode of the light amplification tube. Inside of the light
amplification tube, the light is electronically amplified and projected as a yellowish green glow on
a screen that is then seen by the viewer. The two most important characteristics for the NV are the
 characteristics of the NV tube and optics of the unit. Internationally accepted terminology classifies
the NV tubes in I, II, or III generation (with certain intermediate levels of I+ and II+ gen.).

Generation I+ (Super I+)

This is the next modification of the Gen. I NV tube with a fiber optics plate being installed at the front
or at the back of a tube. This modification allows for an improvement of the image resolution and prevents d
istortion from other light sources in a field of view. Tubes of Gen. I+ have light amplification of approx. 1 000 times,
while the photocathode sensitivity increases to min. 280 mA/lm. Resolution in the center is 45–50 lp/mm.

NV units built with the Gen I+ tubes differ from the Gen. I units by increased image quality, lower distortions and
 better viewing distance in passive or active mode (with an IR illuminator). These scopes work well in an urban environment.
In the open space, the units are effective with the ambient light levels down to ¼ of a moon. When light conditions are lower,
 an IR illuminator is needed. The cost of the Gen. I+ tubes is in 4–9 times higher than the cost of the regular Gen. I. Our
 company manufactures units «Dedal- 220» and sight scope «Dedal- 210» using the Gen. I+ tubes.

Note. The Buyer should take into consideration that some producers use the designation Gen. I+ for their devices Gen I. It
 often misleads buyers because in fact tubes Gen. I have a resolution not higher than 38–40 pl/mm. We use the designation Super Gen I+
in our English advertising to make clear for the buyers peculiarities of the tubes Gen I+ with high resolution.