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Laser rangefinder

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A long range laser rangefinder is capable of measuring distance up to 20 km; mounted on a tripod with an angular mount. The resulting system also provides azimuth and elevation measurements.
A long range laser rangefinder is capable of measuring distance up to 20 km; mounted on a tripod with an angular mount. The resulting system also provides azimuth and elevation measurements.

A laser rangefinder, also known as a laser telemeter, is a rangefinder that uses a laser beam to determine the distance to an object. The most common form of laser rangefinder operates on the time of flight principle by sending a laser pulse in a narrow beam towards the object and measuring the time taken by the pulse to be reflected off the target and returned to the sender. Due to the high speed of light, this technique is not appropriate for high precision sub-millimeter measurements, where triangulation and other techniques are often used.

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Laser

Laser

A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word "laser" is an acronym for "light amplification by stimulated emission of radiation". The first laser was built in 1960 by Theodore H. Maiman at Hughes Research Laboratories, based on theoretical work by Charles Hard Townes and Arthur Leonard Schawlow.

Distance

Distance

Distance is a numerical or occasionally qualitative measurement of how far apart objects or points are. In physics or everyday usage, distance may refer to a physical length or an estimation based on other criteria. Since spatial cognition is a rich source of conceptual metaphors in human thought, the term is also frequently used metaphorically to mean a measurement of the amount of difference between two similar objects or a degree of separation. Most such notions of distance, both physical and metaphorical, are formalized in mathematics using the notion of a metric space.

Time of flight

Time of flight

Time of flight (ToF) is the measurement of the time taken by an object, particle or wave to travel a distance through a medium. This information can then be used to measure velocity or path length, or as a way to learn about the particle or medium's properties. The traveling object may be detected directly or indirectly.

Time

Time

Time is the continued sequence of existence and events that occurs in an apparently irreversible succession from the past, through the present, into the future. It is a component quantity of various measurements used to sequence events, to compare the duration of events or the intervals between them, and to quantify rates of change of quantities in material reality or in the conscious experience. Time is often referred to as a fourth dimension, along with three spatial dimensions.

Speed of light

Speed of light

The speed of light in vacuum, commonly denoted c, is a universal physical constant that is exactly equal to 299,792,458 metres per second. According to the special theory of relativity, c is the upper limit for the speed at which conventional matter or energy can travel through space.

Triangulation

Triangulation

In trigonometry and geometry, triangulation is the process of determining the location of a point by forming triangles to the point from known points.

Pulse

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.

Precision

The precision of the instrument is determined by the rise or fall time of the laser pulse and the speed of the receiver. One that uses very sharp laser pulses and has a very fast detector can range an object to within a few millimeters.

Range and range error

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 air bubbles in the air acting as lenses ranging in size from microscopic to roughly half the height of the laser beam's path above 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 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 1200 ft (365 m), the target, if in proximity to the earth, 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 have to be taken into account.

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Calculation

Time-of-flight principles applied to laser range-finding.
Time-of-flight principles applied to laser range-finding.

The distance between point A and B 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 is the integer number of wave half-cycles of the round-trip and ΔN the remaining fractional part.

Technologies

An OLS-27 IRST with laser rangefinder on the Sukhoi Su-27
An OLS-27 IRST with laser rangefinder on the Sukhoi Su-27

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 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 (H2O, CO2, CH4, O2 etc.) to calculate 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.[1]

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Sukhoi Su-27

Sukhoi Su-27

The Sukhoi Su-27 is a Soviet-origin twin-engine supermaneuverable fighter aircraft designed by Sukhoi. It was intended as a direct competitor for the large US fourth-generation jet fighters such as the Grumman F-14 Tomcat and McDonnell Douglas F-15 Eagle, with 3,530-kilometre (1,910 nmi) range, heavy aircraft ordnance, sophisticated avionics and high maneuverability. The Su-27 was designed for air superiority missions, and subsequent variants are able to perform almost all aerial warfare operations. It was designed with the Mikoyan MiG-29 as its complement.

Time of flight

Time of flight

Time of flight (ToF) is the measurement of the time taken by an object, particle or wave to travel a distance through a medium. This information can then be used to measure velocity or path length, or as a way to learn about the particle or medium's properties. The traveling object may be detected directly or indirectly.

Nanosecond

Nanosecond

A nanosecond (ns) is a unit of time in the International System of Units (SI) equal to one billionth of a second, that is, 1⁄1 000 000 000 of a second, or 10−9 seconds.

Interferometry

Interferometry

Interferometry is a technique which uses the interference of superimposed waves to extract information. Interferometry typically uses electromagnetic waves and is an important investigative technique in the fields of astronomy, fiber optics, engineering metrology, optical metrology, oceanography, seismology, spectroscopy, quantum mechanics, nuclear and particle physics, plasma physics, remote sensing, biomolecular interactions, surface profiling, microfluidics, mechanical stress/strain measurement, velocimetry, optometry, and making holograms.

Atmospheric chemistry

Atmospheric chemistry

Atmospheric chemistry is a branch of atmospheric science in which the chemistry of the Earth's atmosphere and that of other planets is studied. It is a multidisciplinary approach of research and draws on environmental chemistry, physics, meteorology, computer modeling, oceanography, geology and volcanology and other disciplines. Research is increasingly connected with other areas of study such as climatology.

Water vapor

Water vapor

Water vapor, water vapour or aqueous vapor is the gaseous phase of water. It is one state of water within the hydrosphere. Water vapor can be produced from the evaporation or boiling of liquid water or from the sublimation of ice. Water vapor is transparent, like most constituents of the atmosphere.[4] Under typical atmospheric conditions, water vapor is continuously generated by evaporation and removed by condensation. It is less dense than most of the other constituents of air and triggers convection currents that can lead to clouds.

Carbon dioxide

Carbon dioxide

Carbon dioxide (chemical formula CO2) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is transparent to visible light but absorbs infrared radiation, acting as a greenhouse gas. It is a trace gas in Earth's atmosphere at 421 parts per million (ppm), or about 0.04% by volume (as of May 2022), having risen from pre-industrial levels of 280 ppm. Burning fossil fuels is the primary cause of these increased CO2 concentrations and also the primary cause of climate change. Carbon dioxide is soluble in water and is found in groundwater, lakes, ice caps, and seawater. When carbon dioxide dissolves in water, it forms carbonate and mainly bicarbonate (HCO−3), which causes ocean acidification as atmospheric CO2 levels increase.

Methane

Methane

Methane ( MEH-thayn, MEE-thayn) is a chemical compound with the chemical formula CH4 (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The relative abundance of methane on Earth makes it an economically attractive fuel, although capturing and storing it poses technical challenges due to its gaseous state under normal conditions for temperature and pressure.

Allotropes of oxygen

Allotropes of oxygen

There are several known allotropes of oxygen. The most familiar is molecular oxygen, present at significant levels in Earth's atmosphere and also known as dioxygen or triplet oxygen. Another is the highly reactive ozone. Others are:Atomic oxygen, a free radical. Singlet oxygen, one of two metastable states of molecular oxygen. Tetraoxygen, another metastable form. Solid oxygen, existing in six variously colored phases, of which one is O8 and another one metallic.

Applications

Military

An American soldier with a GVS-5 laser rangefinder
An American soldier with a GVS-5 laser rangefinder

Rangefinders provide an exact distance to targets located beyond the distance of point-blank shooting to snipers and artillery. They can also be used for military reconnaissance and engineering.

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 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.

A Dutch ISAF sniper team displaying their Accuracy International AWSM .338 Lapua Magnum rifle and VECTOR IV[2] Leica/Vectronix laser rangefinder binoculars
A Dutch ISAF sniper team displaying their Accuracy International AWSM .338 Lapua Magnum rifle and VECTOR IV[2] Leica/Vectronix laser rangefinder binoculars

The more powerful models of rangefinders measure distance up to 25 km and are normally installed either on a tripod or directly on a vehicle 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 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.[3]

3-D modeling

This LIDAR scanner may be used to scan buildings, rock formations, etc., to produce a 3D model. The LIDAR can aim its laser beam in a wide range: its head rotates horizontally, a mirror flips vertically. The laser beam is used to measure the distance to the first object on its path.
This LIDAR scanner may be used to scan buildings, rock formations, etc., to produce a 3D model. The LIDAR can aim its laser beam in a wide range: its head rotates horizontally, a mirror flips vertically. The laser beam is used to measure the distance to the first object on its path.

Laser rangefinders are used extensively in 3-D object recognition, 3-D object modelling, and 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 3-D models with as little error as possible. One of the advantages that laser rangefinders offer over other methods of computer vision is that the computer does not need to correlate features from two images to determine depth information as in stereoscopic methods.

Laser rangefinders used in computer vision applications often have depth resolutions of tenths of millimeters or less. This can be achieved by using triangulation or refraction measurement techniques as opposed to the time of flight techniques used in LIDAR.

Forestry

Laser rangefinder TruPulse used for forest inventories (in combination with Field-Map technology)
Laser rangefinder TruPulse used for forest inventories (in combination with Field-Map technology)

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.

Sports

Laser rangefinders may be effectively used in various sports that require precision distance measurement, such as golf, hunting, and archery. Some of 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 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.[4] 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.

Industrial production processes

An important application is the use of laser rangefinder technology during the automation of stock management systems and production processes in steel industry.

Laser measuring tools

Laser rangefinder: Bosch GLM 50 C
Laser rangefinder: Bosch GLM 50 C

Laser rangefinders are also used in several industries like construction, renovation and real estate as an alternative to a tape measure, 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 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 the tape measure is typically more accurate, laser measuring tools can be calibrated to be generally reliable when taking several measurements. Laser measuring tools typically include the ability to produce some simple calculations, such as the area or volume of a room, as well as switch between imperial and metric units. These devices can be found in hardware stores and online marketplaces.

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Point-blank range

Point-blank range

Point-blank range is any distance over which a certain firearm can hit a target without the need to compensate for bullet drop, and can be adjusted over a wide range of distances by sighting in the firearm. If the bullet leaves the barrel parallel to the sight, the bullet, like any object in flight, is pulled downwards by gravity, so for distant targets, the shooter must point the firearm above the target to compensate. But if the target is close enough, bullet drop will be negligible so the shooter can aim the gun straight at the target. If the sights are set so that the barrel has a small upward tilt, the bullet starts by rising and later drops. This results in a weapon that hits too low for very close targets, too high for intermediate targets, too low for very far targets, and point blank at two distances in between. For a .270 Winchester, as an example, the bullet first crosses the line of sight at about 23 metres as it is rising and has a maximum impact above the line of sight of approximately 75 mm and crosses the line of sight again at about 250 metres. This is for a 130 grain hunting bullet. Therefore point blank range for a deer size target is about 275 metres . Point-blank range will vary by a weapon's external ballistics characteristics and the allowable error at the target; the flatter the bullet's trajectory or the larger the target, the longer the point-blank range will be.

Binoculars

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 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.

Monocular

Monocular

A monocular is a compact refracting telescope used to magnify images of distant objects, typically using an optical prism to ensure an erect image, instead of using relay lenses like most telescopic sights. The volume and weight of a monocular are typically less than half of a pair of binoculars with similar optical properties, making it more portable and also less expensive. This is because binoculars are essentially a pair of monoculars packed together — one for each eye. As a result, monoculars only produce two-dimensional images, while binoculars can use two parallaxed images to produce binocular vision, which allows stereopsis and depth perception.

Night vision

Night vision

Night vision is the ability to see in low-light conditions, either naturally with scotopic vision or through a night-vision device. Night vision requires both sufficient spectral range and sufficient intensity range. Humans have poor night vision compared to many animals such as cats, foxes and rabbits, in part because the human eye lacks a tapetum lucidum, tissue behind the retina that reflects light back through the retina thus increasing the light available to the photoreceptors.

International Security Assistance Force

International Security Assistance Force

The International Security Assistance Force (ISAF) was a multinational military mission in Afghanistan from 2001 to 2014. It was established by United Nations Security Council Resolution 1386 pursuant to the Bonn Agreement, which outlined the establishment of a permanent Afghan government following the U.S. invasion in October 2001. ISAF's primary goal was to train the Afghan National Security Forces (ANSF) and assist Afghanistan in rebuilding key government institutions; it gradually took part in the broader war in Afghanistan against the Taliban insurgency.

Accuracy International AWM

Accuracy International AWM

The Accuracy International AWM is a bolt-action sniper rifle manufactured by Accuracy International designed for magnum rifle cartridges. The Accuracy International AWM is also unofficially known as the AWSM, which typically denotes AWM rifles chambered in .338 Lapua Magnum.

Barr and Stroud

Barr and Stroud

Barr & Stroud Limited was a pioneering Glasgow optical engineering firm. They played a leading role in the development of modern optics, including rangefinders, for the Royal Navy and for other branches of British Armed Forces during the 20th century. There was a non-military arm of the company which made medical equipment, like photocoagulators and electronic filters, some of which were used by the BBC. The company and its intellectual property passed through Pilkington group to Thales Optronics. The Barr and Stroud name was sold on to an importer of optical equipment, who use the trademarked name for a line of binoculars and similar instruments.

Hughes Aircraft Company

Hughes Aircraft Company

The Hughes Aircraft Company was a major American aerospace and defense contractor founded on February 14, 1934 by Howard Hughes in Glendale, California, as a division of Hughes Tool Company. The company was known for producing, among other products, the Hughes H-4 Hercules aircraft, the atmospheric entry probe carried by the Galileo spacecraft, and the AIM-4 Falcon guided missile.

Ruby

Ruby

A ruby is a pinkish red to blood-red colored gemstone, a variety of the mineral corundum. Ruby is one of the most popular traditional jewelry gems and is very durable. Other varieties of gem-quality corundum are called sapphires. Ruby is one of the traditional cardinal gems, alongside amethyst, sapphire, emerald, and diamond. The word ruby comes from ruber, Latin for red. The color of a ruby is due to the element chromium.

3D object recognition

3D object recognition

In computer vision, 3D object recognition involves recognizing and determining 3D information, such as the pose, volume, or shape, of user-chosen 3D objects in a photograph or range scan. Typically, an example of the object to be recognized is presented to a vision system in a controlled environment, and then for an arbitrary input such as a video stream, the system locates the previously presented object. This can be done either off-line, or in real-time. The algorithms for solving this problem are specialized for locating a single pre-identified object, and can be contrasted with algorithms which operate on general classes of objects, such as face recognition systems or 3D generic object recognition. Due to the low cost and ease of acquiring photographs, a significant amount of research has been devoted to 3D object recognition in photographs.

Computer vision

Computer vision

Computer vision tasks include methods for acquiring, processing, analyzing and understanding digital images, and extraction of high-dimensional data from the real world in order to produce numerical or symbolic information, e.g. in the forms of decisions. Understanding in this context means the transformation of visual images into descriptions of the world that make sense to thought processes and can elicit appropriate action. This image understanding can be seen as the disentangling of symbolic information from image data using models constructed with the aid of geometry, physics, statistics, and learning theory.

Field-Map

Field-Map

Field-Map is a proprietary integrated tool designed for programmatic field data collection from IFER – Monitoring and Mapping Solutions, Ltd.

Price

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.[5][6]

Safety

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.[7] Regardless of the safety rating, direct eye contact should always be avoided. Most laser rangefinders for military use exceed the laser class 2 energy levels.

Source: "Laser rangefinder", Wikipedia, Wikimedia Foundation, (2023, January 25th), https://en.wikipedia.org/wiki/Laser_rangefinder.

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References
  1. ^ Siozos, Panagiotis; Psyllakis, Giannis; Velegrakis, Michalis (2022-11-02). "A continuous‐wave, lidar sensor based on water vapour absorption lines at 1.52 μm". Remote Sensing Letters. 13 (11): 1164–1172. doi:10.1080/2150704X.2022.2127130. ISSN 2150-704X. S2CID 252826003.
  2. ^ "En: Choose Business Unit". www.vectronix.ch. Archived from the original on 3 March 2016. Retrieved 13 January 2022.
  3. ^ Finlayson, D. M.; Sinclair, B. (January 1999). Advances in Lasers and Applications. ISBN 9780750306324.
  4. ^ Are golf rangefinders legal for tournament play?
  5. ^ "Laser Rangefinder Cost". OpticsPlanet. Retrieved 2017-04-11.
  6. ^ "LRF Price Compare".
  7. ^ "Laser Standards and Classifications". www.rli.com. Retrieved 2017-04-11.
External links

Media related to Laser range finders at Wikimedia Commons

  • [1] A brief write-up on Hunting Rangefinder and its types.

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