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Frequently asked questions What are night-vision devices used for? In general, night vision devices are widely used for among others: law enforcement and security; self-defense; hunting; camping and hiking; wildlife viewing; boating and maritime. How night-vision works? In Generation II and III systems, the objective lens collects light that you cannot see with your naked eye and focuses it on the image intensifier. Inside the image intensifier a photocathode absorbs this light energy and converts it into electrons. These electrons are then drawn toward a phosphor screen but first pass through a microchannel plate that multiplies those thousands of times. When this highly intensified electron image strikes the phosphor screen, it causes the screen to emit light that you can see. Since the phosphor screen emits this light in exactly the same pattern and degrees of intensity as the light that is collected by the objective lens, the bright nighttime image you see in the eyepiece corresponds precisely to the outside scene you are viewing. What is Generation I? Typically uses an S-20 photocathode, electrostatic inversion, and electron acceleration to achieve gain. Because of higher photosensitivity, Gen I was the first truly passive image intensifier. Gen I is characterized by geometric distortion, poor performance at low light levels, and blooming. What is Generation II? Usually an S-25 photocathode (with photosensitivity of 240+ uA/lm and a microchannel plate to achieve gain. Can be found with either electrostatic or fiber-optic inversion. Gen II tubes provide satisfactory performance at low light levels and exhibit low distortion. What is Generation III? Uses gallium-arsenide for the photocathode and a microchannel plate for gain. The microchannel plate is also coated with an ion barrier film to increase tube life. Produces more than 800 uA/lm in the 450 to 950 nanometer (near-infrared) region of the spectrum. Gen III provides very good to excellent low-light-level performance, long tube life. How far can I see? It varies anywhere from 10 to 400 ft. The maximum viewing distance depends on the conditions of use. Overcast conditions, fog, rain etc. may reduce the effective distance of a night vision viewer. An infrared illuminator will increase your viewing range, especially in enclosed spaces like a warehouse, garage or other enclosed parameters. Can I use a night vision device in extremely low light, or absolutely no light conditions? While it is true that your night vision device needs some available light to work, it is still possible to see a bright image in low light or no light conditions with the use of an infrared illuminator, which can be either built-in or attached to the device. Most models in our product line come with a built-in infrared illuminator. On a few models, the infrared illuminator is available as an option. What is the maximum effective distance of the infrared illuminator? It varies from model to model, typically anywhere between 75 and 250 ft. What type of light source can be harmful to a night vision device? Your night vision device is designed to assist your viewing in the dark. It may be harmful and will damage the device if you use it during the daytime or whenever there is sufficient light to see the object. Also, keep in mind that strong direct light, such as projectors, car headlamps and strong flashlights and so on, may be harmful to your night vision unit if you direct your device at the source of these intense lights. TERMINOLOGY Automatic Brightness Control - is an electric feature that automatically reduces voltages to the microchannel plate (2nd & 3rd Gen) of the intensifier tube to keep the image intensifier 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 constant level. Biocular - is a device (generally optical) designed for use with both eyes viewing through a single exit pupil. The term may be distinguished from binocular in that biocular instruments contain elements that are common to both eyes. Black Spots - are cosmetic blemishes in the image intensifier or can be dirt or debris between the lenses. Black spots that are in the image intensifier do not affect the performance or reliability of a night vision device and some number of varying size are inherent in the manufacturing processes. Spots due to dirt or debris between the lenses should be removed by careful cleaning if the system is designed for interchanging optics. Blooming - is a momentary loss of the night vision image due to intensifier tube overloading by a bright light source. When such a bright light source comes into the night vision devices view, the entire night vision scene becomes much brighter, "whiting out" objects within the field of view. Blooming is common in Generation 0 and 1 devices. Bright-Source Protection (BSP) - is an electronic function that reduces the voltage to the photocathode (usually 1st Gen) 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. Cosmetic Quality (spots) - during the manufacturing process, microscopic spots may develop in the tube. This is caused by minute defects in the fiber optics or mixture on the photocathode. These cosmetic defects in no way hinder the reliability or function of the system. All tubes have some of these spots to one degree or another. The best tube will have the fewest spots, and therefore the best image quality. Daylight Lens Cover - is usually made of soft plastic or rubber with a pinhole that allows a small amount of light to enter the objective lens of a night vision device. This should be used for training purposes only, and is not recommended for an extended period of time. Diopter - is the unit of measure used to define eye correction or the refractive power of a lens. Usually, adjustments to an optical eyepiece accommodate for differences in individual eyesight. Equivalent Background Illumination (EBI) - is the amount you see in an image tube that is turned on but there is no light at all on the photocathode; it is affected by temperature where the warmer night-vision device, the brighter the background illumination. EBI is measured in lumens per square centimeter (lm/cm2) wherein the lower the value the better. The EBI level determines the lowest light level at which you can detect something. Below this light level, objects will be masked by the EBI. Eye Relief- is the distance your eyes must be from the last element of the eyepiece in order to achieve the optimal image area. Exit Pupil - in an optical system, the rays of light passing through the system will be limited by either the edges of one of the components such as the eyepiece lens, or by an internal aperture. The image passing through the entrance side of the optical system is the entrance pupil. The image passing out the exit side is the exit pupil. This image forms a small disk containing all of the light collected by the optics from the entire field-of-view. Field-of-View (FOV) - sometimes called the angle of coverage or angle of view, is the diameter of the imaged area when viewed through an optic. It is the area in the eyepiece of an optical instrument in which the image is visible. Figure of Merit (FOM) - is an image intensification tube specification designation, calculated on line pair per mm x signal to noise. Focal length - is the distance from the optical center of a lens (or, the secondary principal point for a complex lens like a camera lens) to the focal point (sensor) when the lens is focused on an object at infinity. Its a primary physical characteristic of a lens which can be measured in an optical lab. It remains the same no matter what camera the lens is mounted on. A 7mm focal length lens is always a 7mm focal length lens and a 300mm focal length lens is always a 300mm focal length lens. Gain - is also called brightness gain or luminance gain. This is the number of times a night vision device amplifies light input. It is usually measured as tube gain or system gain. Tube gain is measured as the light output divided by the light input. This figure is usually seen in values of tens of thousands. If tube gain is pushed too high, the tube will be "noisier" and the signal-to-noise ratio may go down. On the other hand system gain is measured as light output divided by the light input and is what the user actually sees. System gain is usually seen in the thousands. In any night vision device, the tube gain is reduced by the system lenses and is affected by the quality of the optics or any filters, therefore, system gain is a more important measurement to the user. Gallium Arsenide (GaAs) - is the semiconductor material used in manufacturing of the Gen III photocathode. Highlight Shutoff - an image intensifier protection feature incorporating a sensor, microprocessor and circuit breaker. This feature will turn the system off during periods of extreme bright light conditions. Infra-Red Illuminators - All Starlight scopes need some light to amplify. This means that if you were in complete darkness you could not see. Interpupillary Adjustment - is the distance between the user eyes (pupils) and the adjustment of binocular optics to adjust for differences in individuals. Improperly adjusted binoculars will display a scene that appears egg-shaped or as a reclining figure-8. IR Laser - are high-power devices providing long-range illumination capability. Ranges of several thousand meters are common. Most are not eye-safe and are restricted in use. Each IR laser should be marked with a warning label. Luminance Gain - is the ability of a tube or a system to amplify the light it detects. The higher number will be the better the luminance gain. Magnification - is the magnifying power of the lens. Four power (4X) indicates that the image will appear four times larger than if viewed with a 1X lens. Microchannel Plate (MCP) - is a metal-coated glass disk that multiplies the electrons produced by the photocathode. An MCP is found only in Gen II and Gen III systems. These devices normally have anywhere from 2 to 6 million holes (or channels) in them. Electrons entering a channel strike the wall and knock off additional electrons which in turn knock off more electrons producing a cascading effect. MCP eliminate the distortion characteristic of Gen 0 and Gen I systems. The number of holes in an MCP is a major factor in determining resolution. Objective Lens - the objective lens assembly collects the available light energy and focuses it on the photocathode (front end of the image intensifier tube). It is housed in an assembly that is used for distance focusing. A coating is placed on the inside portion of the lens that filters out specific wavelengths, thus allowing the use of properly modified interior lighting. Optical coatings - reduce reflection both internally and externally and thereby increase the amount of light that reaches the eye which improves brightness and contrast. Below are the types of coatings: • Coated: Lens surfaces are coated to improve light transmission capability. • Fully Coated: All air-to-glass surfaces are coated. • Multi-Coated: One or more surfaces or lenses have been coated with multiple films and all surfaces are coated at least once. • Fully Multi-Coated: All air-to glass surfaces have multiple films. • Magenta Coating: Reduced reflection, fully coated optics throughout. • Rubicon® Coated: This coating consists of 14 layers of multi-coating on the objective lenses and is characterized by ruby-red coloring on the objectives. It provides excellent bright daylight and glare conditions viewing because it filters out red light. Signal-to-Noise Ratio - is the computed ratio of measured data from photosensitivity, gain, and resolution. The higher the ratio, the better the ability of the tube to produce a clear image under very dark conditions.

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