What is the principle of infrared rangefinder?

Rangefinder is a kind of track calculation instrument, which is used to measure the target distance and calculate the track. There are many forms of rangefinder, usually a long cylinder, which consists of objective lens, eyepiece and ranging knob, and is used to measure the target distance. Rangefinder is a kind of ranging instrument designed according to the principles of optics, acoustics and electromagnetism. \x0d\ There are three kinds of infrared rangefinders: laser infrared rangefinder, infrared rangefinder and ultrasonic rangefinder. At present, laser infrared rangefinder, infrared rangefinder and ultrasonic rangefinder mainly refer to them, but they have been eliminated because of their limited measuring distance and low measuring accuracy. Laser infrared rangefinder is an instrument that uses laser to accurately measure the target distance. When the laser infrared rangefinder works, it emits a very fine laser beam to the target, and the photoelectric element receives the laser beam reflected by the target. The timer measures the time from transmitting to receiving the laser beam and calculates the distance from the observer to the target. \x0d\ rangefinder has measuring distance and accuracy, and it is also an electronic device, so the choice of brand is very important. The range finder of international famous brands will be far superior to the laser infrared range finder of miscellaneous brands in performance. \x0d\ I. Classification of rangefinders \x0d\ Rangefinders can be divided into the following three categories according to the basic principle of ranging: \x0d\ 1. Laser rangefinder \x0d\ Laser rangefinder is an instrument that uses laser to accurately measure the distance of a target. When the laser rangefinder works, it emits a very fine laser beam to the target, and the photoelectric element receives the laser beam reflected by the target. The timer measures the time from transmitting to receiving the laser beam and calculates the distance from the observer to the target. \ x0d \ x0d \ laser rangefinder is the most widely used rangefinder at present, which can be divided into hand-held laser rangefinder (measuring distance 0-300m) and telescopic laser rangefinder (measuring distance 500-20000m). \x0d\ At present, laser rangefinder is the mainstream in the market. The top two brands of handheld laser rangefinder in the world are Leica and Bosch, and the mainstream handheld laser rangefinder is shown on the right. \ x0d \ x0d \ telescope laser rangefinder, long-distance laser rangefinder, which is widely used outdoors at present. The top four brands of telescope laser rangefinder in the world are tuya Dede, Doctor, Aofa and Nikon. The four brands have their own characteristics in products. According to the data published in the American Journal of Laser Technology 20 1 1, the global sales champion of single product in 201/was tuya YP900. This rangefinder measures accurately and responds quickly. \x0d\2。 Ultrasonic rangefinder \x0d\ Ultrasonic rangefinder measures according to the characteristics of obstacles reflecting ultrasonic waves. The ultrasonic transmitter emits ultrasonic waves in a certain direction and starts timing at the same time. Ultrasonic waves travel in the air and will return immediately when they encounter obstacles on the way. The ultrasonic receiver will stop timing immediately when it receives the reflected wave. 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 rangefinder, because the ultrasonic wave is greatly influenced by the surrounding environment, the measuring distance is generally short and the measuring accuracy is relatively low. At present, the scope of use is not very wide, but the price is relatively low, generally around several hundred. \x0d\3。 Infrared rangefinder \x0d\ An instrument that uses modulated infrared light to accurately measure the distance, and the measuring range is generally 1-5km. It uses the principle of non-diffusion when infrared rays propagate: because the refractive index of infrared rays passing through other substances is very small, the long-distance rangefinder will consider infrared rays, and the propagation of infrared rays takes time. When the infrared ray is emitted from the range finder and reflected by the reflector, it can be received by the range finder, and then the distance \x0d\ can be calculated according to the time from emission to reception and the propagation speed of the infrared ray. The advantages of infrared ranging are cheap, easy to manufacture and safe, but the disadvantages are low precision, short distance and poor directivity. \x0d\ Infrared rangefinder and ultrasonic rangefinder technology are relatively backward. Now generally speaking, infrared rangefinder is laser rangefinder. \x0d\ II。 Principle of laser infrared rangefinder \x0d\ Laser infrared rangefinder generally adopts two methods for ranging: pulse method and phase method. The process of pulse ranging is as follows: the laser emitted by the rangefinder is reflected by the measured object and then received by the rangefinder, and the rangefinder also records the round-trip time of the laser. Half of the product of the speed of light and the round trip time is the distance from the rangefinder to the measured object. The ranging accuracy of pulse method is generally about+/-65438 0 meters. In addition, the blind area of this range finder is generally around 15 meters. Laser ranging is a ranging method in light wave ranging. If it takes t for light to travel back and forth between point A and point B at speed C in air, then the distance d between point A and point B can be expressed as follows. \x0d\D=ct/2\x0d\ where: \x0d\D—— Measure the distance between Station A and bilibili; \ x0d \ c- the propagation speed of light in the atmosphere; \ x0d \ t-the time required for light to go back and forth to A and B once. \x0d\ As can be seen from the above formula, measuring the distance between a and b is actually measuring the time t of light propagation. According to the different methods of measuring time, laser rangefinder can usually be divided into pulse and phase measurement forms. \x0d\x0d\ phase laser rangefinder \ x0d \ phase laser rangefinder modulates the amplitude of laser beam with the frequency of radio band, measures the phase delay caused by the modulation light going back and forth to the measuring line, and then converts the distance represented by this phase delay according to the wavelength of the modulation light. That is, the indirect method is used to measure the time required for light to pass through the round-trip measuring line, as shown in the figure. \x0d\ phase laser rangefinder is generally used for precision ranging. Because of its high accuracy, which is generally millimeter level, in order to effectively reflect the signal, the measuring target is limited to a specific point commensurate with the accuracy of the instrument. This range finder is equipped with a mirror, which is called the cooperative target. \x0d\ If the angular frequency of the modulated light is Ω, and the phase delay generated by a round trip on the distance d to be measured is Ω, then the corresponding time t can be expressed as: \ x0d \ t =φ/ω\ x0d \ Substitute this relationship into formula (3-6), and the distance d can be expressed as \ x0d \ d =1/. X0d \ u- unit length, the value is equal to 1/4 modulation wavelength \ x0d \ n- the number of modulation half wavelengths included in the line. \ x0d \ Δφ—— the part where the phase delay is less than π when the signal goes back and forth from the measuring line. \ x0d \ δ n —— The fractional part of the modulated wave contained in the measuring line is less than half a wavelength. \ x0d \ δ n = φ/ω \ x0d \ Under the given modulation and standard atmospheric conditions, the frequency c/(4πf) is a constant, at this time, the measurement of distance becomes the measurement of the number of half wavelengths contained in the survey line and the measurement of the fractional part less than half wavelength, that is, the measurement of n or φ. Due to the development of modern precision machining technology and radio phase measurement technology, the measurement of φ has reached a high precision. \x0d\ In order to measure the phase angle φ less than π, different methods can be used for measurement. Generally, delayed phase measurement and digital phase measurement are the most widely used. At present, short-range laser rangefinders all use the principle of digital phase measurement to obtain φ. \x0d\ As mentioned above, in general, the phase laser rangefinder uses a continuous laser beam with a modulated signal. In order to achieve high ranging accuracy, it is necessary to equip a cooperative target. At present, the hand-held laser rangefinder is another new type of pulse laser rangefinder, which is not only small in size and light in weight, but also adopts the pulse broadening subdivision technology of digital phase measurement, which can achieve millimeter-level accuracy without cooperating with the target, and the measurement range has exceeded 100m, which can directly, quickly and accurately display the distance. It is the latest length measurement standard instrument in short-range precision engineering survey and building area survey. At present, the most widely used are DISTO series hand-held laser rangefinder, Tuyard Trueyard laser rangefinder and Orfa laser rangefinder produced by Leica Company. \x0d\ What are the main brands of rangefinders? 20 12 10 selected by American optical times magazine 10 global rangefinder brand: \x0d\\x0d\ 1. . LECIA Laser Infrared Range Finder Short-distance Handheld Range Finder \ x0d \ Through the survey of nearly 1000 users in the United States and the survey of market share and customer reputation of the range finder. Leica has a high reputation in the field of surveying and mapping, mainly producing high-precision, short-distance hand-held rangefinders, occupying a very large market share in the field of hand-held rangefinders, and has always been the global sales champion of hand-held rangefinders. In recent two years, its leading position in the field of hand-held rangefinder has been strongly impacted by Bosch of Germany, and Bosch has surpassed Lecia Leica in several regional markets. \x0d\ II。 . TRUEYARD laser infrared rangefinder Long-distance telescope rangefinder \ x0d \ x0d \ tuya is a world-renowned outdoor optical brand, which plays a very important role in the field of long-distance telescope laser infrared rangefinder. Long-term occupation of the world's first brand of telescope rangefinder sales. According to the survey data of Time magazine in 20 12 years, more than 52% of telescope rangefinder customers use tuya laser infrared rangefinder. Tuya telescope rangefinder has the characteristics of accurate measurement, simple operation, powerful function and high cost performance. \x0d\ tuya De, as an old professional manufacturer of telescope rangefinder, has a number of patented production technologies for telescope rangefinder. At present, among the major brands, tuya Germany is one of the few brands that can produce integrated models of ranging+height measurement+angle measurement+height difference measurement. None of the other three competitors have such technology. Nikon can only produce all-in-one ranging and height measurement, Doctor can only produce all-in-one ranging and angle measurement, and Orfa can only produce all-in-one ranging and height measurement. Officially, tuya has been occupying the world because of its leading technology. \x0d\ tuya Germany is ahead in technology because tuya Germany is the fastest measuring model among all laser infrared rangefinders, and all models have the function of continuous ranging. \x0d\\x0d\ The most famous models in tuya are SP 1500, 1500m, which is very cost-effective. In 20 1 1 year, tuya Germany introduced the YP series of high-quality models, and the YP900H with a price of less than 3,500 yuan became the most dazzling model in 20 1 1 year. It is a high-quality product of tuya Dede rangefinder, which is far superior to other brands in function. \ x0d \ 2065438+In June 2002, tuya's new generation SP 1500H went on the market, marking a new world of multifunctional laser infrared rangefinder. SP 1500H, 1500 m ranging can not only measure height, range and angle, but also increase the pilot function of 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 the product went on the market, it was favored by customers and became the sales champion of a new generation of multifunctional laser infrared rangefinder. \x0d\ III。 Bosch laser infrared rangefinder is a rookie of short-distance handheld rangefinder, which matches Leica. \x0d\ Bosch also has a high reputation in the field of measuring instruments, surpassing Leica in many products. In the short-distance handheld rangefinder, Bosch started later than Leica, but it has grown rapidly in recent two years, which directly threatens Leica's monopoly position in the global handheld rangefinder. The hand-held rangefinder with the same accuracy and distance will be cheaper than Leica 10%, so the cost performance is very high. \x0d\ IV。 Austrian laser infrared rangefinder telescope laser infrared rangefinder rookie, growing very rapidly \ x0d \ x0d \ Austrian is a world-famous brand of night vision equipment. As the world's first brand of night vision equipment, Aofa entered the field of telescope laser infrared rangefinder a little late, but since 2002, Aofa has become the focus of attention in the industry. With its customer base and annual growth rate of 30%, it has become the second largest telescope rangefinder brand in 20 1 1 America. \x0d\ ORF rangefinder is cost-effective, which is the perfect unity of performance and price. Orr rangefinder is characterized by simple operation, ultra-fast ranging speed and high cost performance. Very famous models include 600A, and 1800A\x0d\ band 1800m ranging. Dr. v. Bushnell laser infrared rangefinder \x0d\ has a very high position in the field of outdoor optics, because it is the most complete brand of outdoor optical product line at present, including telescope rangefinder, binoculars, bird-watching glasses and night vision device. Doctor's binoculars have always been the number one in the world. In terms of telescope rangefinder, it has maintained the third position in the United States for many years. \x0d\ doctor telescope rangefinder, with many products, is the brand with the most product models at present. Its telescope rangefinder products are very suitable for golf and hunting. The functional aspect is biased towards these two aspects of design. But as a common field application, the operation is relatively complicated. Another point is that the product lacks the function of height measurement. But its rangefinder has a good observation effect. \x0d\ The most famous model of Bosch's rangefinder is ELITE 1500(205 100), which is a very legendary rangefinder and has sold more than 1 10,000 units worldwide. This is a 1500 yard rangefinder, which is made in China compared with other styles of doctors. ELITE 1500 is the only rangefinder in Japan with exquisite workmanship. This rangefinder is cost-effective, with a price of 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 metering and charging. \x0d\ The updated product of Dr. Bosch is 20 1965, which is the latest product of Dr. Bosch in 20 12 years. Compared with other rangefinder products of Dr. Bosch, its accuracy is improved to 0.5 yards, and a faster chip is adopted, which makes the ranging speed of 20 1965 faster. Need a high-precision rangefinder, which is a better choice. 20 1965 is a multifunctional rangefinder, which can measure angles and horizontal distances. Another model with the same appearance is Doctor Energy 20 1960(Z6), which is a golf rangefinder. Very famous in the field of golf. But for ordinary use, because it only provides a measurement mode of flagpole measurement, its adaptability to the environment will be poor, and in some environments, the measurement is inaccurate. Relatively speaking, 20 1965 is more cost-effective. \x0d\ Another very famous model of Dr Bosch is the short-range 202205, which is an 850-yard short-range rangefinder. It is characterized by small and exquisite appearance, fast measurement speed and high cost performance.