The rangefinder is a track estimation instrument used to measure target distance and perform track estimation. There are many forms of rangefinders, usually a long cylinder, consisting of an objective lens, an eyepiece, and a distance measuring knob, and are used to measure the distance to a target. A distance meter is an instrument designed based on the principles of optics, acoustics and electromagnetic waves for distance measurement. \x0d\ There are three types of infrared rangefinders: laser infrared, infrared and ultrasonic. Currently, rangefinders mainly refer to laser infrared rangefinders, infrared rangefinders and ultrasonic rangefinders. Due to the limited measurement distance, the measurement accuracy is very low. Low has now been eliminated. Laser infrared rangefinder is an instrument that uses laser to accurately measure the distance of a target. When the laser infrared rangefinder is working, it emits a very thin laser beam towards the target. The photoelectric element receives the laser beam reflected by the target. The timer measures the time from emission to reception of the laser beam and calculates the distance from the observer to the target. \x0d\A rangefinder has the ability to measure distance and measurement accuracy, and it is an electronic device at the same time, so the choice of brand is very important. Rangefinders from internationally renowned brands will be far better in performance than brand-name laser infrared rangefinders. \x0d\1. Classification of rangefinders\x0d\Rangefinders can be divided into the following three categories based on the basic principles of distance measurement:\x0d\1. Laser rangefinder\x0d\Laser rangefinders use lasers to accurately measure the distance to a target. instrument. When the laser rangefinder is working, it emits a very thin laser beam towards the target. The photoelectric element receives the laser beam reflected by the target. The timer measures the time from emission to reception of the laser beam and calculates the distance from the observer to the target. \x0d\\x0d\Laser rangefinder is currently the most widely used rangefinder. Laser rangefinder can be classified into handheld laser rangefinder (measuring distance 0-300 meters), telescope laser rangefinder (measuring distance Distance 500-20000 meters). \x0d\Currently, the mainstream ones on the market are laser rangefinders. The top two brands of handheld laser rangefinders in the world are Leica and Bosch. The picture on the right shows a mainstream handheld laser rangefinder. \x0d\\x0d\Telescope laser rangefinder is a long-distance laser rangefinder. It is currently widely used outdoors. The top four brands of telescope laser rangefinders in the world are Tuyad, Bushnell, Olfa and Nikon. . Each of the four brands has its own characteristics in terms of products. In 2011, according to data released by the American Laser Technology Magazine, the global single product sales champion in 2011 was Tuyad YP900. This rangefinder has accurate measurement and fast response speed. \x0d\2. Ultrasonic range finder \x0d\ Ultrasonic range finder measures based on the characteristics of ultrasonic waves reflected back when encountering obstacles. The ultrasonic transmitter emits ultrasonic waves in a certain direction and starts timing at the same time. The ultrasonic waves propagate in the air and return immediately when they encounter obstacles on the way. When the ultrasonic receiver receives the reflected wave, it immediately interrupts and stops the timing. By continuously detecting the echo reflected by the obstacle after the generated wave is emitted, the time difference T between transmitting the ultrasonic wave and receiving the echo is measured, and then the distance L is calculated. \x0d\\x0d\Ultrasonic range finder, because ultrasonic waves are greatly affected by the surrounding environment, the general measurement distance is relatively short and the measurement accuracy is relatively low. At present, the scope of use is not very wide, but the price is relatively low, generally around a few hundred. \x0d\3. Infrared range finder\x0d\ An instrument that uses modulated infrared light for precise distance measurement. The measurement range is generally 1-5 kilometers. The non-diffusion principle of infrared ray propagation is used: because the refractive index of infrared rays is very small when passing through other substances, long-distance rangefinders will consider infrared rays, and the propagation of infrared rays takes time. When infrared rays are emitted from the rangefinder When it encounters a reflective object, it is reflected back and is received by the rangefinder. Then the distance can be calculated based on the time from when the infrared ray is emitted to when it is received and the propagation speed of the infrared ray\x0d\The advantages of infrared ranging are cheap, easy to make, safe, and disadvantages It has low accuracy, short distance and poor directionality. \x0d\Infrared rangefinder and ultrasonic rangefinder technology are relatively backward. Now the general concept is infrared rangefinder, which also refers to laser rangefinder. \x0d\2. Principle of laser infrared range finder \x0d\ Laser infrared range finders generally use two methods to measure distance: pulse method and phase method. The process of pulse distance measurement is as follows: the laser emitted by the rangefinder is reflected by the object being measured and then received by the rangefinder. The rangefinder records the round-trip time of the laser at the same time. Half the product of the speed of light and the round-trip time is the distance between the rangefinder and the object being measured. The accuracy of distance measurement by pulse method is generally around +/-1 meter. In addition, the measurement blind zone of this type of rangefinder is generally about 15 meters. \x0d\Laser ranging is a distance measurement method in light wave ranging. If light propagates in the air at a speed c and the time required for a round trip between two points A and B is t, then the distance between two points A and B D can be expressed as follows. \x0d\D=ct/2\x0d\In the formula:\x0d\D——The distance between measuring points A and B;\x0d\c——The speed of light propagating in the atmosphere;\x0d\t—— The time it takes for light to travel back and forth between A and B. \x0d\ It can be seen from the above formula that to measure the distance between A and B is actually to measure the time t of light propagation. According to the different measurement time methods, laser rangefinders can usually be divided into two measurement forms: pulse type and phase type.

\x0d\\x0d\Phase laser rangefinder\x0d\The phase laser rangefinder uses the frequency of the radio band to amplitude modulate the laser beam and measure the phase delay generated by the modulated light traveling back and forth to the measurement line once, and then based on The wavelength of the modulated light is converted into the distance represented by this phase delay. That is, the indirect method is used to measure the time required for light to travel back and forth from the measurement line, as shown in the figure. \x0d\ Phase laser rangefinders are generally used in precision ranging. Due to its high accuracy, generally at the millimeter level, in order to effectively reflect the signal and limit the measured target to a specific point commensurate with the accuracy of the instrument, this rangefinder is equipped with a reflector called a cooperative target. mirror. \x0d\If the angular frequency of the modulated light is ω, and the phase delay generated by one round trip on the distance D to be measured is φ, then the corresponding time t can be expressed as: \x0d\t=φ/ω\x0d\ Substituting this relationship into ( 3-6) The distance D can be expressed as\x0d\D=1/2ct=1/2c·φ/ω=c/(4πf)(Nπ+Δφ)\x0d\=c/4f(N+ΔN)= U(N+)\x0d\Where:\x0d\φ——The total phase delay caused by the signal going back and forth to the measuring line once. \x0d\ω——The angular frequency of the modulation signal, ω=2πf. \x0d\U——Unit length, the value is equal to 1/4 modulation wavelength\x0d\N——The number of modulated half-wavelengths contained in the measuring line. \x0d\Δφ——The phase delay of the signal traveling back and forth to the measuring line is less than π. \x0d\ΔN——The fractional part of the modulated wave contained in the measuring line that is less than half the wavelength. \x0d\ΔN=φ/ω\x0d\Under given modulation and standard atmospheric conditions, the frequency c/(4πf) is a constant. At this time, the measurement of distance becomes the measurement sum of the number of half-wavelengths contained in the measuring line. The measurement of the fractional part less than half the wavelength is to measure N or φ. Due to the development of modern precision machining technology and radio phase measurement technology, the measurement of φ has reached a very high accuracy. \x0d\In order to measure the phase angle φ that is less than π, different methods can be used to measure it. The most commonly used ones are delayed phase measurement and digital phase measurement. At present, short-range laser rangefinders use the principle of digital phase measurement to obtain it. φ. \x0d\As mentioned above, under normal circumstances, phase laser rangefinders use continuous emission of laser beams with modulated signals. In order to obtain high accuracy in ranging, it is necessary to configure a cooperative target. The handheld laser rangefinder currently launched is a pulse Another new type of laser rangefinder. It is not only small in size and light in weight, but also uses digital phase measurement pulse broadening and subdivision technology. It can achieve millimeter-level accuracy without a cooperative target. The measurement range has exceeded 100m, and can Quickly and accurately display distance directly. It is the latest length measurement standard instrument for short-range precision precision engineering measurement and building area measurement. The most commonly used ones are the DISTO series handheld laser rangefinders produced by Leica, the Trueyard laser rangefinder telescope and the Orfa laser rangefinder. \x0d\When purchasing a rangefinder, what are the main brands of rangefinders? In October 2012, the American Optical Times selected the top 10 rangefinder brands in the world through a survey of nearly 10,000 users in the United States, a survey of rangefinder brand market share and customer reputation:\x0d\\x0d\ one. LECIA Leica laser infrared rangefinder short-range handheld rangefinder \x0d\\x0d\ Leica has a very high reputation in the field of measurement and mapping. It mainly produces high-precision short-range handheld rangefinders. It occupies a very large market share in the field of handheld rangefinders and has always been the global sales champion of handheld rangefinders. In the past two years, its leadership position in the field of handheld rangefinders has been strongly impacted by Bosch of Germany. Bosch has surpassed LECIA in many regional markets. Leica. \x0d\ 2. TRUEYARD is a world-renowned outdoor optical brand and plays a very important role in the field of long-distance telescope laser infrared rangefinders. It has long been the number one selling brand of telescope rangefinders in the world. A 2012 US Times survey of the United States showed that among customers of telescope rangefinders, more than 52% used Tuyad laser infrared rangefinders. The Tuyad telescope rangefinder has the characteristics of accurate measurement, easy operation, powerful functions and high cost performance. \x0d\As a long-established professional manufacturer of telescope rangefinders, Tuyade has a number of patented production technologies for telescope rangefinders. Among the major brands currently, Tuyad is one of the few brands that can produce an all-in-one model that can measure distance + height measurement + angle measurement + height difference measurement. The other three major competitors do not have such technology, and Nikon can only produce it. It is an all-in-one machine for measuring distance + height measurement, while Bushnell can only produce an all-in-one machine for measuring height + angle measurement, and Orfa can only produce an all-in-one machine for measuring height + angle measurement + distance measurement. Officially, Tuyad is technically inferior to The reason for its leading position is that it has always occupied the number one sales position in the world. \x0d\ Another reason why Tuyad is technologically advanced is that Tuyad has the fastest measurement speed among all laser infrared rangefinders, and all models have the function of continuous ranging. \x0d\\x0d\Tuyade's most well-known model is the SP1500, a model with an ultra-long range of 1500 meters and a very cost-effective model.

In 2011, Tuyade launched the YP series of high-quality models. Its YP900H, priced at less than 3,500 yuan, became the most dazzling model of the year in 2011. It is Tuyade's range measurement + height measurement + angle measurement integrated range measurement. The quality of the instrument far exceeds other brands in terms of functionality. \x0d\In June 2012, Tuya's new generation SP1500H was launched, and the standard multifunctional laser infrared rangefinder entered a new world. SP1500H, 1500-meter ranging, in addition to measuring height, distance and angle, adds the leading function of measuring height difference (absolute height). At the same time, the function of continuous angle measurement without turning on the infrared transmitter is added. Two months after its launch, this product was favored by customers and became the sales champion of the new generation of multifunctional laser infrared rangefinders. \x0d\Three. BOSCH Bosch laser infrared rangefinder is a new short-distance handheld rangefinder, almost as close to Leica\x0d\Bosch also has a very high reputation in the field of measuring instruments, surpassing Leica in many products. In terms of short-distance handheld rangefinders, Bosch started later than Leica, but has grown rapidly in the past two years, directly threatening Leica's monopoly on global handheld rangefinders. The price of a handheld rangefinder with the same accuracy and distance will be about 10% lower than that of Leica, making it extremely cost-effective. \x0d\ Four. ORPHA Orfa Laser Infrared Rangefinder Telescope Laser Infrared Rangefinder Newcomer, growing very rapidly \x0d\\x0d\ ORPHA is a world-renowned brand of night vision equipment. As the world's number one sales brand of night vision equipment, ORPHA Alpha entered the field of telescope laser infrared rangefinders a little later, but since entering this field in 2002, Alpha has become the focus of the industry, relying on its customer base and influence in the field of night vision devices. With an annual growth rate of 30%, it became the second largest telescope rangefinder brand in the United States in 2011. \x0d\The Orfa rangefinder has a very high cost performance and is the perfect combination of performance and price. The Orfa rangefinder is characterized by simple operation, ultra-fast ranging speed, and ultra-high cost performance. The very famous models are the 600A and the 1800A with a range of 1800 meters. BUSHNELL Laser Infrared Rangefinder \x0d\ Bushnell can be said to have a very high position in the field of outdoor optics, because it is currently the brand with the most complete outdoor optical product line, including telescope rangefinders, binoculars, and birdwatching scopes and night vision goggles. Bushnell binoculars have always maintained the number one position in the world. In terms of telescopic rangefinders, it has maintained the third position in the United States for many years. \x0d\ Bushnell telescope rangefinder has many products and is currently the brand with the most product models. Its telescopic rangefinder products are ideal for golf, as well as hunting. Functional aspects are designed to favor these two aspects. However, when used in general fields, the operation is relatively cumbersome. Another point is that the product lacks the function of measuring height. But the observation effect of its rangefinder is very good. \x0d\The most famous model of Bushnell's rangefinder is ELITE1500 (205100), which is a very legendary rangefinder with a cumulative global sales of more than 1 million units. This is a 1500-yard rangefinder. Compared to Bushnell's other models, which are all made in China, the ELITE1500 is the only rangefinder produced in Japan with exquisite workmanship. This rangefinder is very cost-effective, priced at less than 3,000 yuan, which is very attractive. In addition, its main features are very long battery life, simple and convenient operation, and accurate measurement accounting. \x0d\ Bushnell's updated product is 201965, which is Bushnell's latest product in 2012. Compared with Bushnell's other rangefinder products, its accuracy is improved to 0.5 yards, and a faster chip is used to make the 201965 range faster. . If you need a high-precision rangefinder, this is a better choice. 201965 is a multifunctional rangefinder that can measure angles and horizontal distances. Another model with the same appearance is Bushnell 201960 (Z6), which is a golf-specific rangefinder. Very famous in the golf field. However, for ordinary use, since it only provides one measurement mode, flagpole measurement, its adaptability to the environment will be relatively poor, and in some environments, the measurement will be inaccurate. Relatively speaking, 201965 has a higher cost performance. \x0d\ Another very famous model of Bushnell is the short-range 202205, which is an 850-yard short-range rangefinder. It is characterized by its compact and exquisite appearance, fast measurement, and extremely high cost performance.