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111-569: The pulse may be coded to reduce the chance that the rangefinder can be jammed . It is possible to use Doppler effect techniques to judge whether the object is moving towards or away from the rangefinder, and if so, how fast. The precision of an instrument is correlated with the rise time , divergence, and power of its laser pulse, as well as the quality of its optics and onboard digital signal processing . Environmental factors can significantly reduce range and accuracy: In good conditions, skilled operators using precision laser rangefinders can range

222-612: A convex objective and a concave eyepiece lens . The Galilean design has the advantage of presenting an erect image but has a narrow field of view and is not capable of very high magnification. This type of construction is still used in very cheap models and in opera glasses or theater glasses. The Galilean design is also used in low magnification binocular surgical and jewelers' loupes because they can be very short and produce an upright image without extra or unusual erecting optics, reducing expense and overall weight. They also have large exit pupils, making centering less critical, and

333-415: A "brighter" and sharper image than an 8×25, even though both enlarge the image an identical eight times. The larger front lenses in the 8×40 also produce wider beams of light (exit pupil) that leave the eyepieces. This makes it more comfortable to view with an 8×40 than an 8×25. A pair of 10×50 binoculars is better than a pair of 8×40 binoculars for magnification, sharpness and luminous flux. Objective diameter

444-475: A ( monocular ) telescope, binoculars give users a three-dimensional image : each eyepiece presents a slightly different image to each of the viewer's eyes and the parallax allows the visual cortex to generate an impression of depth . Almost from the invention of the telescope in the 17th century the advantages of mounting two of them side by side for binocular vision seems to have been explored. Most early binoculars used Galilean optics ; that is, they used

555-458: A 2-axis pseudo-collimation and will only be serviceable within a small range of interpupillary distance settings, as conditional aligned binoculars are not collimated for the full interpupillary distance setting range. Some binoculars use image-stabilization technology to reduce shake at higher magnifications. This is done by having a gyroscope move part of the instrument, or by powered mechanisms driven by gyroscopic or inertial detectors, or via

666-515: A better sensation of depth. Porro prism designs have the added benefit of folding the optical path so that the physical length of the binoculars is less than the focal length of the objective. Porro prism binoculars were made in such a way to erect an image in a relatively small space, thus binoculars using prisms started in this way. Porro prisms require typically within 10 arcminutes ( ⁠ 1 / 6 ⁠ of 1 degree ) tolerances for alignment of their optical elements ( collimation ) at

777-470: A better type of Crown glass in 1888, and instrument maker Carl Zeiss resulted in 1894 in the commercial introduction of improved 'modern' Porro prism binoculars by the Carl Zeiss company . Binoculars of this type use a pair of Porro prisms in a Z-shaped configuration to erect the image. This results in wide binoculars, with objective lenses that are well separated and offset from the eyepieces , giving

888-404: A complex mix of factors like the quality of optical glass used and various applied optical coatings and not just the magnification and the size of objective lenses. The twilight factor for binoculars can be calculated by first multiplying the magnification by the objective lens diameter and then finding the square root of the result. For instance, the twilight factor of 7×50 binoculars is therefore

999-429: A complex production process. In binoculars with roof prisms the light path is split into two paths that reflect on either side of the roof prism ridge. One half of the light reflects from roof surface 1 to roof surface 2. The other half of the light reflects from roof surface 2 to roof surface 1. If the roof faces are uncoated, the mechanism of reflection is Total Internal Reflection (TIR). In TIR, light polarized in

1110-407: A delay to indicate incorrect range. Transponders may alternatively increase return echo strength to make a small decoy appear to be a larger target. Target modifications include radar absorbing coatings and modifications of the surface shape to either "stealth" a high-value target or enhance reflections from a decoy. Dispersal of small aluminium strips called chaff is a common method of changing

1221-492: A double convex singlet between them or may all be achromatic doublets. These eyepieces tend not to perform as well as Kellner eyepieces at high power because they suffer from astigmatism and ghost images. However they have large eye lenses, excellent eye relief, and are comfortable to use at lower powers. High-end binoculars often incorporate a field flattener lens in the eyepiece behind their prism configuration, designed to improve image sharpness and reduce image distortion at

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1332-468: A double image. Even slight misalignment will cause vague discomfort and visual fatigue as the brain tries to combine the skewed images. Alignment is performed by small movements to the prisms, by adjusting an internal support cell or by turning external set screws , or by adjusting the position of the objective via eccentric rings built into the objective cell. Unconditional aligning (3-axis collimation, meaning both optical axes are aligned parallel with

1443-479: A full size submarine. Most navies additionally equip ships with decoy launchers. Binoculars Binoculars or field glasses are two refracting telescopes mounted side-by-side and aligned to point in the same direction, allowing the viewer to use both eyes ( binocular vision ) when viewing distant objects. Most binoculars are sized to be held using both hands, although sizes vary widely from opera glasses to large pedestal -mounted military models. Unlike

1554-528: A given viewer). Binoculars can be generally used without eyeglasses by myopic (near-sighted) or hyperopic (far-sighted) users simply by adjusting the focus a little farther. Most manufacturers leave a little extra available focal-range beyond the infinity-stop/setting to account for this when focusing for infinity. People with severe astigmatism, however, will still need to use their glasses while using binoculars. Some binoculars have adjustable magnification, zoom binoculars , such as 7-21×50 intended to give

1665-737: A group of Japanese battleships. The spark-gap transmitters in the Russian stations generated senseless noise while the Japanese were making attempts to coordinate their efforts in the bombing of a Russian naval base. Germany and United Kingdom interfered with enemy communications along the western front during World War I while the Royal Navy tried to intercept German naval radio transmissions. There were also efforts at sending false radio signals, having shore stations send transmissions using ships' call signs, and jamming enemy radio signals. On

1776-421: A large drop in brightness at high zoom. Models also have to match the magnification for both eyes throughout the zoom range and hold collimation to avoid eye strain and fatigue. These almost always perform much better at the low power setting than they do at the higher settings. This is natural, since the front objective cannot enlarge to let in more light as the power is increased, so the view gets dimmer. At 7×,

1887-687: A laser rangefinder on them is difficult. The first commercial laser rangefinder was the Barr & Stroud LF1, developed in association with Hughes Aircraft , which became available in 1965. This was then followed by the Barr & Stroud LF2, which integrated the rangefinder into a tank sight, and this was used on the Chieftain tank in 1969, the first vehicle so-equipped with such a system. Both systems used ruby lasers. Laser rangefinders are used extensively in 3D object recognition , 3D object modelling, and

1998-466: A lower reflectivity than silver. Using vacuum-vaporization technology, modern designs use either aluminum, enhanced aluminum (consisting of aluminum overcoated with a multilayer dielectric film) or silver. Silver is used in modern high-quality designs which are sealed and filled with nitrogen or argon to provide an inert atmosphere so that the silver mirror coating does not tarnish. Porro prism and Perger prism binoculars and roof prism binoculars using

2109-902: A mount designed to oppose and damp the effect of shaking movements. Stabilization may be enabled or disabled by the user as required. These techniques allow binoculars up to 20× to be hand-held, and much improve the image stability of lower-power instruments. There are some disadvantages: the image may not be quite as good as the best unstabilized binoculars when tripod-mounted, stabilized binoculars also tend to be more expensive and heavier than similarly specified non-stabilized binoculars. Binoculars housings can be made of various structural materials. Old binoculars barrels and hinge bridges were often made of brass . Later steel and relatively light metals like aluminum and magnesium alloys were used, as well as polymers like ( fibre-reinforced ) polycarbonate and acrylonitrile butadiene styrene . The housing can be rubber armored externally as outer covering to provide

2220-618: A non-slip gripping surface, absorption of undesired sounds and additional cushioning/protection against dents, scrapes, bumps and minor impacts. Because a typical binocular has 6 to 10 optical elements with special characteristics and up to 20 atmosphere-to-glass surfaces, binocular manufacturers use different types of optical coatings for technical reasons and to improve the image they produce. Lens and prism optical coatings on binoculars can increase light transmission, minimize detrimental reflections and interference effects, optimize beneficial reflections, repel water and grease and even protect

2331-402: A relatively narrow IPDs. Anatomic conditions like hypertelorism and hypotelorism can affect IPD and due to extreme IPDs result in practical impairment of using stereoscopic optical products like binoculars. The two telescopes in binoculars are aligned in parallel (collimated), to produce a single circular, apparently three-dimensional, image. Misalignment will cause the binoculars to produce

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2442-415: A result, effective modern anti-reflective lens coatings consist of complex multi-layers and reflect only 0.25% or less to yield an image with maximum brightness and natural colors. These allow high-quality 21st century binoculars to practically achieve at the eye lens or ocular lens measured over 90% light transmission values in low light conditions. Depending on the coating, the character of the image seen in

2553-414: A roof prism for polychromatic light several phase-correction coating layers are superimposed, since every layer is wavelength and angle of incidence specific. The P-coating was developed in 1988 by Adolf Weyrauch at Carl Zeiss . Other manufacturers followed soon, and since then phase-correction coatings are used across the board in medium and high-quality roof prism binoculars. This coating suppresses

2664-666: A room. These devices can be found in hardware stores and online marketplaces. Laser rangefinders can vary in price, depending on the quality and application of the product. Military grade rangefinders need to be as accurate as possible and must also reach great distances. These devices can cost hundreds of thousands of dollars. For civilian applications, such as hunting or golf, devices are more affordable and much more readily accessible. Laser rangefinders are divided into four classes and several subclasses. Laser rangefinders available to consumers are usually laser class 1 or class 2 devices and are considered relatively eye-safe. Regardless of

2775-515: A ship's hull and wake to reduce sound transmission. Surface ships tow noisemakers like the AN/SLQ-25 Nixie to decoy homing torpedoes. Submarines can deploy similar acoustic device countermeasures (or ADCs) from a 3-inch (75-mm) signal launching tube. United States ballistic missile submarines could deploy the Mark 70 MOSS ( Mobile submarine simulator ) decoy from torpedo tubes to simulate

2886-532: A small scale, like the Perger prism that offers a significantly reduced axial offset compared to traditional Porro prism designs . Roof prism binoculars may have appeared as early as the 1870s in a design by Achille Victor Emile Daubresse. In 1897 Moritz Hensoldt began marketing pentaprism based roof prism binoculars. Most roof prism binoculars use either the Schmidt–Pechan prism (invented in 1899) or

2997-510: A suspected Syrian nuclear weapons site, the Israel Air Force used electronic warfare to take control of Syrian airspace prior to the attack. Israeli electronic warfare (EW) systems took over Syria's air defense systems, feeding them a false sky-picture while Israel Air Force jets crossed much of Syria, bombed their targets and returned. Basic radar ECM strategies are (1) radar interference, (2) target modifications, and (3) changing

3108-414: A target to within a meter at distances on the order of three kilometers. Despite the beam being narrow, it will eventually spread over long distances due to the divergence of the laser beam, as well as due to scintillation and beam wander effects, caused by the presence of water droplets in the air acting as lenses ranging in size from microscopic to roughly half the height of the laser beam's path above

3219-522: A tripod or directly on a vehicle, ship, jet, helicopter or gun platform. In the latter case the rangefinder module is integrated with on-board thermal, night vision and daytime observation equipment. The most advanced military rangefinders can be integrated with computers. To make laser rangefinders and laser-guided weapons less useful against military targets, various military arms may have developed laser-absorbing paint for their vehicles. Regardless, some objects don't reflect laser light very well and using

3330-628: A vacuum chamber with maybe thirty or more different superimposed vapor coating layers deposits, making it a complex production process. Binoculars using either a Schmidt–Pechan roof prism , Abbe–Koenig roof prism or an Uppendahl roof prism benefit from phase coatings that compensate for a loss of resolution and contrast caused by the interference effects that occur in untreated roof prisms. Porro prism and Perger prism binoculars do not split beams and therefore they do not require any phase coatings. In binoculars with Schmidt–Pechan or Uppendahl roof prisms, mirror coatings are added to some surfaces of

3441-483: A wide variety of computer vision -related fields. This technology constitutes the heart of the so-called time-of-flight 3D scanners . In contrast to the military instruments, laser rangefinders offer high-precision scanning abilities, with either single-face or 360-degree scanning modes. A number of algorithms have been developed to merge the range data retrieved from multiple angles of a single object to produce complete 3D models with as little error as possible. One of

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3552-477: A wider range of wavelengths and angles by using several superimposed layers with different refractive indices. The anti-reflective multi-coating Transparentbelag* (T*) used by Zeiss in the late 1970s consisted of six superimposed layers. In general, the outer coating layers have slightly lower index of refraction values and the layer thickness is adapted to the range of wavelengths in the visible spectrum to promote optimal destructive interference via reflection in

3663-480: Is interference between light from the two paths causing a distortion of the Point Spread Function and a deterioration of the image. Resolution and contrast significantly suffer. These unwanted interference effects can be suppressed by vapor depositing a special dielectric coating known as a phase-correction coating or P-coating on the roof surfaces of the roof prism. To approximately correct

3774-403: Is physical vapor deposition which includes evaporative deposition with maybe seventy or more different superimposed vapor coating layers deposits, making it a complex production process. This multilayer coating increases reflectivity from the prism surfaces by acting as a distributed Bragg reflector . A well-designed multilayer dielectric coating can provide a reflectivity of over 99% across

3885-516: Is being developed to replace the current AN/ALQ-99 carried on the E/A-18G electronic warfare plane. Planned for adoption around 2020, it will use a small AESA antenna divided into quadrants for all around coverage and retain the capability of highly directional jamming. DARPA 's Precision Electronic Warfare (PREW) project aims to develop a low-cost system capable of synchronizing several simple airborne jamming pods with enough precision to replicate

3996-578: Is capable of providing magnetic azimuth, inclination, and height (length) of targets. Some rangefinders can also measure a target's speed in relation to the observer. Some rangefinders have cable or wireless interfaces to enable them to transfer their measurement(s) data to other equipment like fire control computers. Some models also offer the possibility to use add-on night vision modules. Most handheld rangefinders use standard or rechargeable batteries. The more powerful models of rangefinders measure distance up to 40 km and are normally installed either on

4107-451: Is given by where c is the speed of light and t is the amount of time for the round-trip between A and B. where φ is the phase delay made by the light traveling and ω is the angular frequency of optical wave. Then substituting the values in the equation, In this equation, λ is the wavelength ⁠ c / f ⁠ ; Δφ is the part of the phase delay that does not fulfill π (that is, φ modulo π ); N

4218-441: Is important when looking at birds or game animals that move rapidly, or for a seafarer on the deck of a pitching vessel or observing from a moving vehicle. Narrow exit pupil binoculars also may be fatiguing because the instrument must be held exactly in place in front of the eyes to provide a useful image. Finally, many people use their binoculars at dawn, at dusk, in overcast conditions, or at night, when their pupils are larger. Thus,

4329-484: Is inversely proportional to the magnifying power. It is usually notated in a linear value, such as how many feet (meters) in width will be seen at 1,000 yards (or 1,000 m), or in an angular value of how many degrees can be viewed. Binoculars concentrate the light gathered by the objective into a beam, of which the diameter, the exit pupil , is the objective diameter divided by the magnifying power. For maximum effective light-gathering and brightest image, and to maximize

4440-435: Is the closest point that the binocular can focus on. This distance varies from about 0.5 to 30 m (2 to 98 ft), depending upon the design of the binoculars. If the close focus distance is short with respect to the magnification, the binocular can be used also to see particulars not visible to the naked eye. Binocular eyepieces usually consist of three or more lens elements in two or more groups. The lens furthest from

4551-401: Is the distance the observer must position his or her eye behind the eyepiece in order to see an unvignetted image. The longer the focal length of the eyepiece, the greater the potential eye relief. Binoculars may have eye relief ranging from a few millimeters to 25 mm or more. Eye relief can be particularly important for eyeglasses wearers. The eye of an eyeglasses wearer is typically farther from

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4662-522: Is the integer number of wave half-cycles of the round-trip and Δ N the remaining fractional part. Time of flight - this measures the time taken for a light pulse to travel to the target and back. With the speed of light known, and an accurate measurement of the time taken, the distance can be calculated. Many pulses are fired sequentially and the average response is most commonly used. This technique requires very accurate sub- nanosecond timing circuitry. Multiple frequency phase-shift - this measures

4773-492: Is the use of laser rangefinder technology during the automation of stock management systems and production processes in steel industry. Laser rangefinders are also used in several industries like construction, renovation and real estate as alternatives to tape measures , and was first introduced by Leica Geosystems in 1993 in France . To measure a large object like a room with a tape measure, one would need another person to hold

4884-446: Is usually expressed in millimeters. It is customary to categorize binoculars by the magnification × the objective diameter ; e.g., 7×50 . Smaller binoculars may have a diameter of as low as 22 mm; 35 mm and 50 mm are common diameters for field binoculars; astronomical binoculars have diameters ranging from 70 mm to 150 mm. The field of view of a pair of binoculars depends on its optical design and in general

4995-491: The Abbe–Koenig prism (named after Ernst Karl Abbe and Albert König and patented by Carl Zeiss in 1905) designs to erect the image and fold the optical path. They have objective lenses that are approximately in a line with the eyepieces. Binoculars with roof prisms have been in use to a large extent since the second half of the 20th century. Roof prism designs result in objective lenses that are almost or totally in line with

5106-612: The Abbe–Koenig roof prism configuration do not use mirror coatings because these prisms reflect with 100% reflectivity using total internal reflection in the prism rather than requiring a (metallic) mirror coating. Dielectric coatings are used in Schmidt–Pechan and Uppendahl roof prisms to cause the prism surfaces to act as a dielectric mirror . This coating was introduced in 2004 in Zeiss Victory FL binoculars featuring Schmidt–Pechan prisms. Other manufacturers followed soon, and since then dielectric coatings are used across

5217-581: The Battle of the Beams . During the RAF's night attacks on Germany the extent of electronic countermeasures was much expanded, and a specialised organisation, No. 100 Group RAF , was formed to counter the increasing German night fighter force and radar defences. Cold War developments included anti-radiation missiles designed to home in on enemy radar transmitters. In the 2007 Operation Orchard Israeli attack on

5328-464: The rifleman's rule , but it's usually much easier if you let a rangefinder do it when you are out hunting. In golfing where time is most important, a laser rangefinder comes useful in locating distance to the flag. However not all features are 100% legal for golf tournament play. Many hunters in the eastern U.S. don't need a rangefinder, although many western hunters need them, due to longer shooting distances and more open spaces. An important application

5439-482: The 1890s to supersede them with better prism-based technology. Optical prisms added to the design enabled the display of the image the right way up without needing as many lenses, and decreasing the overall length of the instrument, typically using Porro prism or roof prism systems. The Italian inventor of optical instruments Ignazio Porro worked during the 1860s with Hofmann in Paris to produce monoculars using

5550-548: The 50mm front objective provides a 7.14 mm exit pupil, but at 21×, the same front objective provides only a 2.38 mm exit pupil. Also, the optical quality of a zoom binocular at any given power is inferior to that of a fixed power binocular of that power. Most modern binoculars are also adjustable via a hinged construction that enables the distance between the two telescope halves to be adjusted to accommodate viewers with different eye separation or " interpupillary distance (IPD)" (the distance measured in millimeters between

5661-615: The RBOC (Rapid Blooming Off-board Chaff) launchers found on most surface ships. The BLR-14 Submarine Acoustic Warfare System (or SAWS) provides an integrated receiver, processor, display, and countermeasures launch system for submarines. Infrared homing systems can be decoyed with flares and other infrared countermeasures . Acoustic homing and detection systems used for ships are also susceptible to countermeasures. United States warships use Masker and PRAIRIE (propeller AIR Ingestion and Emission) systems to create small air bubbles around

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5772-400: The accompanying more decisive exit pupil does not permit a practical determination of the low light capability of binoculars. Ideally, the exit pupil should be at least as large as the pupil diameter of the user's dark-adapted eyes in circumstances with no extraneous light. A primarily historic, more meaningful mathematical approach to indicate the level of clarity and brightness in binoculars

5883-407: The advantages offered by laser rangefinders over other methods of computer vision is in not needing to correlate features from two images in order to determine depth-information like stereoscopic methods do. Laser rangefinders used in computer vision applications often have depth resolutions of 0.1 mm or less. This can be achieved by using triangulation or refraction measurement techniques unlike to

5994-616: The alignment of their optical elements by laser or interference (collimation) at an affordable price point is challenging. To avoid the need for later re-collimation, the prisms are generally aligned at the factory and then permanently fixed to a metal plate. These complicating production requirements make high-quality roof prism binoculars more costly to produce than Porro prism binoculars of equivalent optical quality and until phase correction coatings were invented in 1988 Porro prism binoculars optically offered superior resolution and contrast to non-phase corrected roof prism binoculars. In

6105-400: The amount of "lost" light present inside the binocular which would otherwise make the image appear hazy (low contrast). A pair of binoculars with good optical coatings may yield a brighter image than uncoated binoculars with a larger objective lens, on account of superior light transmission through the assembly. The first transparent interference-based coating Transparentbelag (T) used by Zeiss

6216-402: The axis of the hinge used to select various interpupillary distance settings) binoculars requires specialized equipment. Unconditional alignment is usually done by a professional, although the externally mounted adjustment features can usually be accessed by the end user. Conditional alignment ignores the third axis (the hinge) in the alignment process. Such a conditional alignment comes down to

6327-459: The beams reflected from the interfaces, and constructive interference in the corresponding transmitted beams. There is no simple formula for the optimal layer thickness for a given choice of materials. These parameters are therefore determined with the help of simulation programs. Determined by the optical properties of the lenses used and intended primary use of the binoculars, different coatings are preferred, to optimize light transmission dictated by

6438-488: The binoculars under normal daylight can either look "warmer" or "colder" and appear either with higher or lower contrast. Subject to the application, the coating is also optimized for maximum color fidelity through the visible spectrum , for example in the case of lenses specially designed for bird watching. A common application technique is physical vapor deposition of one or more superimposed anti-reflective coating layer(s) which includes evaporative deposition , making it

6549-401: The board in medium and high-quality Schmidt–Pechan and Uppendahl roof prism binoculars. The non-metallic dielectric reflective coating is formed from several multilayers of alternating high and low refractive index materials deposited on a prism's reflective surfaces. The manufacturing techniques for dielectric mirrors are based on thin-film deposition methods. A common application technique

6660-499: The case of the US, German, and Italian air forces, may rely on electronic warfare aircraft to carry them. ECM pods vary widely in power and capability; while many fighter aircraft are capable of carrying an ECM pod, these pods are generally less powerful, capable and of shorter range than the equipment carried by dedicated ECM aircraft, thus making dedicated ECM aircraft an important part of any airforce’s inventory. The Next Generation Jammer

6771-441: The centers of the pupils of the eyes). Most are optimized for the interpupillary distance (typically about 63 mm) for adults. Interpupillary distance varies with respect to age, gender and race. The binoculars industry has to take IPD variance (most adults have IPDs in the 50–75 mm range) and its extrema into account, because stereoscopic optical products need to be able to cope with many possible users, including those with

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6882-475: The daytime exit pupil is not a universally desirable standard. For comfort, ease of use, and flexibility in applications, larger binoculars with larger exit pupils are satisfactory choices even if their capability is not fully used by day. Before innovations like anti-reflective coatings were commonly used in binoculars, their performance was often mathematically expressed. Nowadays, the practically achievable instrumentally measurable brightness of binoculars rely on

6993-460: The difference in phase shift between s- and p- polarization so both paths have the same polarization and no interference degrades the image. In this way, since the 1990s, roof prism binoculars have also achieved resolution values that were previously only achievable with Porro prisms. The presence of a phase-correction coating can be checked on unopened binoculars using two polarization filters. Dielectric phase-correction prism coatings are applied in

7104-443: The directionality of an electronically scanned antenna, avoiding collateral jamming of non-targeted receivers. An expendable active decoy that uses DRFM technology to jam RF based threats has already been developed by Selex ES (merged into Leonardo new name of Finmeccanica since 2017). The system, named BriteCloud , is self-contained within a small canister that is similar to a standard flare cartridge. The 55 mm format of

7215-416: The distance of point-blank shooting to snipers and artillery. They can also be used for military reconnaissance and engineering. Usually tanks use LRF to correct the direct shoot solution. Handheld military rangefinders operate at ranges of 2 km up to 25 km and are combined with binoculars or monoculars . When the rangefinder is equipped with a digital magnetic compass (DMC) and inclinometer it

7326-437: The distance to an object. The light atmospheric absorption attenuation method requires unmodulated incoherent light sources and low-frequency electronics that reduce the complexity of the devices. Due to this, low-cost light sources can be used for range-finding. However, the application of the method is limited to atmospheric measurements or planetary exploration. Rangefinders provide an exact distance to targets located beyond

7437-403: The early 2020s in high-quality binoculars practically became irrelevant. At high-quality price points, similar optical performance can be achieved with every commonly applied optical system. This was 20–30 years earlier not possible, as occurring optical disadvantages and problems could at that time not be technically mitigated to practical irrelevancy. Relevant differences in optical performance in

7548-785: The early 2020s, the commercial offering of Schmidt-Pechan designs exceeds the Abbe-Koenig design offerings and had become the dominant optical design compared to other prism-type designs. Alternative roof prism-based designs like the Uppendahl prism system composed of three prisms cemented together were and are commercially offered on a small scale. The optical system of modern binoculars consists of three main optical assemblies: Although different prism systems have optical design-induced advantages and disadvantages when compared, due to technological progress in fields like optical coatings, optical glass manufacturing, etcetera, differences in

7659-407: The earth. These atmospheric distortions coupled with the divergence of the laser itself and with transverse winds that serve to push the atmospheric heat bubbles laterally may combine to make it difficult to get an accurate reading of the distance of an object, say, beneath some trees or behind bushes, or even over long distances of more than 1 km in open and unobscured desert terrain. Some of

7770-413: The electrical properties of air. Interference techniques include jamming and deception. Jamming is accomplished by a friendly platform transmitting signals on the radar frequency to produce a noise level sufficient to hide echos. The jammer's continuous transmissions will provide a clear direction to the enemy radar, but no range information. Deception may use a transponder to mimic the radar echo with

7881-414: The electromagnetic properties of air to provide confusing radar echos. Radio jamming or communications jamming is the deliberate transmission of radio signals that disrupt communications by decreasing the signal-to-noise ratio to the point where the target communications link is either degraded or denied service. ECM is practiced by nearly all modern military units—land, sea or air. Aircraft, however, are

7992-492: The enemy, or make the real target appear to disappear or move about randomly. It is used effectively to protect aircraft from guided missiles . Most air forces use ECM to protect their aircraft from attack. It has also been deployed by military ships and recently on some advanced tanks to fool laser/IR guided missiles. It is frequently coupled with stealth advances so that the ECM systems have an easier job. Offensive ECM often takes

8103-601: The exit pupil of a 7×21 binocular. Much larger 7×50 binoculars will produce a (7.14 mm) cone of light bigger than the pupil it is entering, and this light will, in the daytime, be wasted. An exit pupil that is too small also will present an observer with a dimmer view, since only a small portion of the light-gathering surface of the retina is used. For applications where equipment must be carried (birdwatching, hunting), users opt for much smaller (lighter) binoculars with an exit pupil that matches their expected iris diameter so they will have maximum resolution but are not carrying

8214-435: The eye piece which necessitates a longer eye relief in order to avoid vignetting and, in the extreme cases, to conserve the entire field of view. Binoculars with short eye relief can also be hard to use in instances where it is difficult to hold them steady. Eyeglasses wearers who intend to wear their glasses when using binoculars should look for binoculars with an eye relief that is long enough so that their eyes are not behind

8325-757: The eyepieces, creating an instrument that is narrower and more compact than Porro prisms and lighter. There is also a difference in image brightness. Porro prism and Abbe–Koenig roof-prism binoculars will inherently produce a brighter image than Schmidt–Pechan roof prism binoculars of the same magnification, objective size, and optical quality, because the Schmidt-Pechan roof-prism design employs mirror-coated surfaces that reduce light transmission . In roof prism designs, optically relevant prism angles must be correct within 2 arcseconds ( ⁠ 1 / 1,800 ⁠ of 1 degree) to avoid seeing an obstructive double image. Maintaining such tight production tolerances for

8436-563: The factory. Sometimes Porro prisms binoculars need their prisms set to be re-aligned to bring them into collimation. Good-quality Porro prism design binoculars often feature about 1.5 millimetres (0.06 in) deep grooves or notches ground across the width of the hypotenuse face center of the prisms, to eliminate image quality reducing abaxial non-image-forming reflections. Porro prism binoculars can offer good optical performance with relatively little manufacturing effort and as human eyes are ergonomically limited by their interpupillary distance

8547-430: The first number in a binocular description (e.g., 7 ×35, 10 ×50), magnification is the ratio of the focal length of the objective divided by the focal length of the eyepiece. This gives the magnifying power of binoculars (sometimes expressed as "diameters"). A magnification factor of 7, for example, produces an image 7 times larger than the original seen from that distance. The desirable amount of magnification depends upon

8658-571: The form of jamming . Self-protecting (defensive) ECM includes using blip enhancement and jamming of missile terminal homers . The first example of electronic countermeasures being applied in a combat situation took place during the Russo-Japanese war . On July 13, 1904, Russian wireless telegraphy stations installed in the Port Arthur fortress and on board Russian light cruisers successfully interrupted wireless communication between

8769-440: The human eye luminous efficiency function variance. Maximal light transmission around wavelengths of 555 nm ( green ) is important for obtaining optimal photopic vision using the eye cone cells for observation in well-lit conditions. Maximal light transmission around wavelengths of 498 nm ( cyan ) is important for obtaining optimal scotopic vision using the eye rod cells for observation in low light conditions. As

8880-546: The image the right way up. In aprismatic binoculars with Keplerian optics (which were sometimes called "twin telescopes"), each tube has one or two additional lenses ( relay lens ) between the objective and the eyepiece. These lenses are used to erect the image. The binoculars with erecting lenses had a serious disadvantage: they are too long. Such binoculars were popular in the 1800s (for example, G. & S. Merz models). The Keplerian "twin telescopes" binoculars were optically and mechanically hard to manufacture, but it took until

8991-497: The intended application, and in most binoculars is a permanent, non-adjustable feature of the device (zoom binoculars are the exception). Hand-held binoculars typically have magnifications ranging from 7× to 10×, so they will be less susceptible to the effects of shaking hands. A larger magnification leads to a smaller field of view and may require a tripod for image stability. Some specialized binoculars for astronomy or military use have magnifications ranging from 15× to 25×. Given as

9102-452: The laser light might reflect off leaves or branches which are closer than the object, giving an early return and a reading which is too low. Alternatively, over distances longer than 360 m, if the target is in proximity to the earth, it may simply vanish into a mirage , caused by temperature gradients in the air in proximity to the heated surface bending the laser light. All these effects must be considered. The distance between point A and B

9213-840: The lens from scratches. Modern optical coatings are composed of a combination of very thin layers of materials such as oxides, metals, or rare earth materials. The performance of an optical coating is dependent on the number of layers, manipulating their exact thickness and composition, and the refractive index difference between them. These coatings have become a key technology in the field of optics and manufacturers often have their own designations for their optical coatings. The various lens and prism optical coatings used in high-quality 21st century binoculars, when added together, can total about 200 (often superimposed) coating layers. Anti-reflective interference coatings reduce light lost at every optical surface through reflection at each surface. Reducing reflection via anti-reflective coatings also reduces

9324-463: The magnification, so compared to 7× binoculars, 10× binoculars offer about half (7² ÷ 10² = 0.49) the depth of field. However, not related to the binoculars optical system, the user perceived practical depth of field or depth of acceptable view performance is also dependent on the accommodation ability (accommodation ability varies from person to person and decreases significantly with age) and light conditions dependent effective pupil size or diameter of

9435-417: The more popular manufacturers are Caddytalk, Opti-logic Corporation, Bushnell, Leupold, LaserTechnology, Trimble, Leica, Newcon Optik, Op. Electronics, Nikon , Swarovski Optik and Zeiss . Many rangefinders from Bushnell come with advanced features, such as ARC (angle range compensation), multi-distance ability, slope, JOLT (Vibrate when the target is locked), and Pin-Seeking. ARC can be calculated by hand using

9546-493: The narrow field of view works well in those applications. These are typically mounted on an eyeglass frame or custom-fit onto eyeglasses. An improved image and higher magnification are achieved in binoculars employing Keplerian optics , where the image formed by the objective lens is viewed through a positive eyepiece lens (ocular). Since the Keplerian configuration produces an inverted image, different methods are used to turn

9657-418: The offset and separation of big (60 mm wide) diameter objective lenses and the eyepieces becomes a practical advantage in a stereoscopic optical product. In the early 2020s, the commercial market share of Porro prism-type binoculars had become the second most numerous compared to other prism-type optical designs. There are alternative Porro prism-based systems available that find application in binoculars on

9768-575: The other hand, there were also attempts by the Ottoman side to jam Allied wireless communications during the Gallipoli campaign . World War II ECM expanded to include dropping chaff (originally called Window), jamming and spoofing radar and navigation signals. German bomber aircraft navigated using radio signals transmitted from ground stations, which the British disrupted with spoofed signals in

9879-514: The outer regions of the field of view. Binoculars have a focusing arrangement which changes the distance between eyepiece and objective lenses or internally mounted lens elements. Normally there are two different arrangements used to provide focus, "independent focus" and "central focusing": With increasing magnification, the depth of field – the distance between the nearest and the farthest objects that are in acceptably sharp focus in an image – decreases. The depth of field reduces quadratic with

9990-473: The phase shift of multiple frequencies on reflection then solves some simultaneous equations to give a final measure. Interferometry - the most accurate and most useful technique for measuring changes in distance rather than absolute distances. Light attenuation by atmospheric absorption - The method measures the attenuation of a laser beam caused by the absorption from an atmospheric compound ( H 2 O , CO 2 , CH 4 , O 2 etc.) to calculate

10101-402: The plane of incidence (p-polarized) and light polarized orthogonal to the plane of incidence (s-polarized) experience different phase shifts. As a consequence, linearly polarized light emerges from a roof prism elliptically polarized. Furthermore, the state of elliptical polarization of the two paths through the prism is different. When the two paths recombine on the retina (or a detector) there

10212-564: The point of focus (also called the eyepoint). Else, their glasses will occupy the space where their eyes should be. Generally, an eye relief over 16 mm should be adequate for any eyeglass wearer. However, if glasses frames are thicker and so significantly protrude from the face, an eye relief over 17 mm should be considered. Eyeglasses wearers should also look for binoculars with twist-up eye cups that ideally have multiple settings, so they can be partially or fully retracted to adjust eye relief to individual ergonomic preferences. Close focus distance

10323-483: The primary weapons in the ECM battle because they can "see" a larger patch of earth than a sea or land-based unit. When employed effectively, ECM can keep aircraft from being tracked by search radars, or targeted by surface-to-air missiles or air-to-air missiles . An aircraft ECM can take the form of an attachable underwing pod or could be embedded in the airframe. Fighter planes using a conventional electronically scanned antenna mount dedicated jamming pods instead or, in

10434-615: The roof prism because the light is incident at one of the prism's glass-air boundaries at an angle less than the critical angle so total internal reflection does not occur. Without a mirror coating most of that light would be lost. Roof prism aluminum mirror coating ( reflectivity of 87% to 93%) or silver mirror coating (reflectivity of 95% to 98%) is used. In older designs silver mirror coatings were used but these coatings oxidized and lost reflectivity over time in unsealed binoculars. Aluminum mirror coatings were used in later unsealed designs because they did not tarnish even though they have

10545-589: The safety rating, direct eye contact should always be avoided. Most laser rangefinders for military use exceed the laser class 2 energy levels. [REDACTED] Media related to Laser range finders at Wikimedia Commons Electronic countermeasures An electronic countermeasure ( ECM ) is an electrical or electronic device designed to trick or deceive radar , sonar , or other detection systems, like infrared (IR) or lasers. It may be used both offensively and defensively to deny targeting information to an enemy. The system may make many separate targets appear to

10656-594: The same prism configuration used in modern Porro prism binoculars. At the 1873 Vienna Trade Fair German optical designer and scientist Ernst Abbe displayed a prism telescope with two cemented Porro prisms. The optical solutions of Porro and Abbe were theoretically sound, but the employed prism systems failed in practice primarily due to insufficient glass quality. Porro prism binoculars are named after Ignazio Porro, who patented this image erecting system in 1854. The later refinement by Ernst Abbe and his cooperation with glass scientist Otto Schott , who managed to produce

10767-436: The second number in a binocular description (e.g., 7× 35 , 10× 50 ), the diameter of the objective lens determines the resolution (sharpness) and how much light can be gathered to form an image. When two different binoculars have equal magnification, equal quality, and produce a sufficiently matched exit pupil (see below), the larger objective diameter produces a "brighter" and sharper image. An 8×40, then, will produce

10878-404: The sharpness, the exit pupil should at least equal the diameter of the pupil of the human eye: about 7 mm at night and about 3 mm in the daytime, decreasing with age. If the cone of light streaming out of the binoculars is larger than the pupil it is going into, any light larger than the pupil is wasted. In daytime use, the human pupil is typically dilated about 3 mm, which is about

10989-555: The smallest and largest IPDs. Children and adults with narrow IPDs can experience problems with the IPD adjustment range of binocular barrels to match the width between the centers of the pupils in each eye impairing the use of some binoculars. Adults with average or wide IPDs generally experience no eye separation adjustment range problems, but straight barreled roof prism binoculars featuring over 60 mm diameter objectives can dimensionally be problematic to correctly adjust for adults with

11100-445: The square root of 7 × 50: the square root of 350 = 18.71. The higher the twilight factor, mathematically, the better the resolution of the binoculars when observing under dim light conditions. Mathematically, 7×50 binoculars have exactly the same twilight factor as 70×5 ones, but 70×5 binoculars are useless during twilight and also in well-lit conditions as they would offer only a 0.14 mm exit pupil. The twilight factor without knowing

11211-447: The sub-high-quality price categories can still be observed with roof prism-type binoculars today because well-executed technical problem mitigation measures and narrow manufacturing tolerances remain difficult and cost-intensive. Binoculars are usually designed for specific applications. These different designs require certain optical parameters which may be listed on the prism cover plate of the binoculars. Those parameters are: Given as

11322-567: The system has undergone flight trials with the Gripen aircraft and the development of a 218 variant is at an advanced stage. The ULQ-6 deception transmitter was one of the earlier shipboard ECM installations. The Raytheon SLQ-32 shipboard ECM package came in three versions providing warning, identification and bearing information about radar-guided cruise missiles. The SLQ-32 V3 included quick reaction electronic countermeasures for cruisers and large amphibious ships and auxiliaries in addition to

11433-408: The tape at the far wall and a clear line straight across the room to stretch the tape. With a laser measuring tool, the job can be completed by one operator with just a line of sight. Although tape measures are technically perfectly accurate, laser measuring tools are much more precise. Laser measuring tools typically include the ability to produce some simple calculations, such as the area or volume of

11544-556: The time of flight techniques used in LIDAR . Special laser rangefinders are used in forestry . These devices have anti-leaf filters and work with reflectors . Laser beam reflects only from this reflector and so exact distance measurement is guaranteed. Laser rangefinders with anti-leaf filter are used for example for forest inventories . Laser rangefinders may be effectively used in various sports that require precision distance measurement, such as golf , hunting , and archery . Some of

11655-422: The user the flexibility of having a single pair of binoculars with a wide range of magnifications, usually by moving a "zoom" lever. This is accomplished by a complex series of adjusting lenses similar to a zoom camera lens . These designs are noted to be a compromise and even a gimmick since they add bulk, complexity and fragility to the binocular. The complex optical path also leads to a narrow field of view and

11766-484: The user's eyes. There are "focus-free" or "fixed-focus" binoculars that have no focusing mechanism other than the eyepiece adjustments that are meant to be set for the user's eyes and left fixed. These are considered to be compromise designs, suited for convenience, but not well suited for work that falls outside their designed hyperfocal distance range (for hand held binoculars generally from about 35 m (38 yd) to infinity without performing eyepiece adjustments for

11877-419: The viewer's eye is called the field lens or objective lens and that closest to the eye the eye lens or ocular lens . The most common Kellner configuration is that invented in 1849 by Carl Kellner . In this arrangement, the eye lens is a plano-concave/ double convex achromatic doublet (the flat part of the former facing the eye) and the field lens is a double-convex singlet. A reversed Kellner eyepiece

11988-436: The weight of wasted aperture. A larger exit pupil makes it easier to put the eye where it can receive the light; anywhere in the large exit pupil cone of light will do. This ease of placement helps avoid, especially in large field of view binoculars, vignetting , which brings to the viewer an image with its borders darkened because the light from them is partially blocked, and it means that the image can be quickly found, which

12099-473: Was developed in 1975 and in it the field lens is a double concave/ double convex achromatic doublet and the eye lens is a double convex singlet. The reverse Kellner provides 50% more eye relief and works better with small focal ratios as well as having a slightly wider field. Wide field binoculars typically utilize some kind of Erfle configuration , patented in 1921. These have five or six elements in three groups. The groups may be two achromatic doublets with

12210-415: Was invented in 1935 by Olexander Smakula . A classic lens-coating material is magnesium fluoride , which reduces reflected light from about 4% to 1.5%. At 16 atmosphere to optical glass surfaces passes, a 4% reflection loss theoretically means a 52% light transmission ( 0.96 = 0.520) and a 1.5% reflection loss a much better 78.5% light transmission ( 0.985 = 0.785). Reflection can be further reduced over

12321-415: Was relative brightness. It is calculated by squaring the diameter of the exit pupil. In the above 7×50 binoculars example, this means that their relative brightness index is 51 (7.14 × 7.14 = 51). The higher the relative brightness index number, mathematically, the better the binoculars are suited for low light use. Eye relief is the distance from the rear eyepiece lens to the exit pupil or eye point. It

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