Laser Range finders

Night Vision Monoculars

Automatic Brightness Control An electronic feature that automatically reduces voltages to the microchannel plate to keep the image intensifier's brightness within optimal limits and protect the tube. The effect of this can be seen when rapidly changing from low-light to high-light conditions; the image gets brighter and then, after a momentary delay, suddenly dims to a constant level.

Black Spots Usually cosmetic blemishes in the image which are inherent in the production process. In other cases, as dirt builds on the lens, black spots are also visible. Black spots resulting from the production process neither influence the image quality nor interfere with night observation. Spots which form due to dirt should be removed carefully with a soft cloth.

Bright-Source Protection An electronic function that reduces the voltage to the photocathode when the night vision device is exposed to bright light sources such as room lights or car lights. BSP protects the image tube from damage and enhances its life; however, it also has the effect of lowering resolution when functioning.

Cycles per Milliradian (cy/mr) Units used to measure system resolution. A milliradian is the angle created by 1 yard at a distance of 1,000 yards. This means that a device that can detect two 1/2-yard objects separated by 1/2 yard at 1,000 yards has a resolution of 1.0 cy/mr. Do not confuse cy/mr with line pair per millimeter. For example, a system can have a 3X lens attached and increase the system resolution by a factor of 3, yet the image intensifier's resolution (measured in lp/mm) has not increased.

Diopter The unit of measure used to define eye correction or the refractive power of a lens. In most cases, an optical eyepiece will accommodate for differences in individual eyesight among users.

Distortion

Three types of distortion are most significant to night vision devices: geometric, "S", and sheer.

 

Geometric distortion is inherent in all Gen 0 and Gen I image intensifiers and in some Gen II image intensifiers that use electrostatic rather than fiber-optic inversion of the image. Geometric distortion is eliminated in image tubes that use a microchannel plate and fiber optics for image inversion; however, some S-distortion can occur in these tubes.

S-distortion results from the twisting operation in manufacturing fiber-optic inverters. Usually S-distortion is very small and is difficult to detect with the unaided eye, Gen III image tubes manufactured to U.S. military standards since 1988 have nearly no perceptible S-distortion.

Sheer distortion can occur in any image tube that uses fiber-optic bundles for the phosphor screen. It appears as a cleavage or dislocation in a straight line viewed in the image area; as though the line were "sheered."

Non-inverting image intensifiers that use microchannel plates and clear glass for the optics are free of distortion. The image intensifier ITT manufactures  is distortion free.

 

Electro-optical transducer Primary system which directs and accelerates the photoelectronic flux taking into account the potential difference between the photocathode and the screen, and forms the electronic image.

Emission Point A pinpoint of bright light in the image area that does not vanish when all light is blocked from the objective lens.

Eye Relief The distance your eyes must be from the farthest element of an eyepiece in order to achieve the optimal image area.

Gain Sometimes referred to as brightness gain. Gain is the number of times a night vision device amplifies light input. For a detailed description of gain and how it can affect performance, please refer to our �First Time Buyer Section�.

Infrared Light radiated with wavelengths longer than those of red light.

Line Pairs per Millimeter (lp/mm) Units used to measure image intensifier resolution.

Lumen The unit denoting the photons perceivable by the human eye per one second.

Photosensitivity The ability of the photocathode material to produce an electrical response when subjected to photons.

Recticle The �neon colored� round aiming device found in many night vision rifle scopes which serves as cross-hairs.

Resolution The ability of an image intensifier or night vision system to distinguish between objects close together. Image intensifier resolution is measured in line pairs per millimeter (lp/mm). For a detailed description of resolution and how it can affect performance