What is a Rangefinder?

A rangefinder refers to a radio navigation device that measures the slope distance between an airplane and a ground response station. It consists of an airborne interrogator and a ground answering station. A method of determining the distance between radio waves by measuring the time required for a radio wave to travel from an airplane to a radio station. In aviation, pulse wave inquiries and answers around 1000MHz are used, and its working distance is about 500km, which is used for air routes. In addition, in order to cooperate with the microwave landing system during approach and landing, a precision rangefinder has been developed, which uses the waveform of the pulse front with a faster ascent rate to improve accuracy, and its working distance is about 40km. Both rangefinders work at the same frequency and are compatible. ^[1]

rangefinder

A rangefinder refers to a radio navigation device that measures the slope distance between an airplane and a ground response station. It consists of an airborne interrogator and a ground answering station. A method of determining the distance between radio waves by measuring the time required for a radio wave to travel from an airplane to a radio station. In aviation, pulse wave inquiries and answers around 1000MHz are used, and its working distance is about 500km, which is used for air routes. In addition, in order to cooperate with the microwave landing system during approach and landing, a precision rangefinder has been developed, which uses the waveform of the pulse front with a faster ascent rate to improve accuracy, and its working distance is about 40km. Both rangefinders work at the same frequency and are compatible. ^[1]

A rangefinder is a tool for measuring length or distance. At the same time, it can be combined with an angle measuring device or module to measure parameters such as angle and area. There are many forms of rangefinders, usually a long cylinder, composed of an objective lens,

Common range finder can be divided into short range from the range ^[2]

1. The laser distance meter brands are:

More than 90% of the rangefinders currently on the market are laser rangefinders:

Switzerland

Laser rangefinders generally use two methods to measure distance: pulse method and phase method. The pulse method ranging process is as follows: the laser emitted by the rangefinder is reflected by the measured object and then received by the rangefinder, and the rangefinder simultaneously records the laser round trip 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 such a rangefinder is generally about 15 meters.

Laser ranging is a kind of ranging method in light wave ranging. If the light travels in the air at a speed c and travels between points A and B once, the distance D between the points A and B can be as follows: Means.

D = ct / 2

In the formula:

Ddistance between two points of measurement stations A and B;

cthe speed of light in the atmosphere;

tthe time needed for light to go back and forth between A and B once.

It can be known from the above formula that to measure the distance A and B is actually to measure the time t of the light propagation. According to the different methods of measuring time, the laser rangefinder can be divided into two types: pulse type and phase type.

Phase laser rangefinder

The phase type laser range finder uses radio frequency to modulate the laser beam amplitude and measure the phase delay generated when the modulated light travels back and forth to the measuring line. Then, the distance represented by this phase delay is converted according to the wavelength of the modulated light. The indirect method is used to measure the time required for the light to pass through the line, as shown in the figure.

Phase laser range finder is generally used in precision ranging. Due to its high accuracy, generally millimeter level, in order to effectively reflect the signal and limit the measurement target to a specific point commensurate with the accuracy of the instrument, this rangefinder is equipped with a reflection called a cooperative target mirror.

If the angular frequency of the modulated light is , and the phase delay caused by one round trip over the distance D to be measured is , the corresponding time t can be expressed as:

t = /

Substituting this relationship into the formula (3-6) distance D can be expressed as

D = 1/2 ct = 1/2 c · / = c / (4f) (N + )

= c / 4f (N + N) = U (N +)

In the formula:

The total phase delay caused by the signal to and from the line once.

the angular frequency of the modulation signal, = 2f.

Uunit length, the value is equal to 1/4 modulation wavelength

Nthe number of modulation half-wavelengths included in the measurement line.

Signal delay caused by the round trip of the signal is less than .

NThe fraction of the modulation wave containing less than half of the wavelength.

N = /

Under the given modulation and standard atmospheric conditions, the frequency c / (4f) is a constant. At this time, the distance measurement becomes the measurement of the number of half-wavelengths included in the line and the measurement of the fractional part less than half-wavelength. Or , due to modern times

Long distance measurement, can measure long distance without reflective plate and low reflectivity;

With synchronous input, multiple sensors can measure simultaneously;

Wide measurement range and short response time;

Compact appearance design, easy to install and operate;

It can measure the distance of various objects (no need for mirror); Add filter to measure the high temperature test object;

Visible light is easy to aim at the test object;

LDM42 response speed up to 50Hz;

The highest measurement accuracy is 3mm, the resolution is 0.1mm;

Output: serial port RS232 / RS422, analog output 4 20mA, analog port and switch value can be set by software;

LDM43 with Profibus DP and SSI bus interface, easy to integrate into industrial field bus;

With external synchronization input;

Laser rangefinders have been widely used in the following areas: electricity, water conservancy, communications, environment, construction, geology, police, firefighting, blasting, marine, aviation, railway, counter-terrorism / military, agriculture, forestry, real estate, leisure / outdoor Sports etc.

Why is there a difference between the so-called "safe" and "unsafe" laser rangefinder ?

As the name suggests, a laser rangefinder is a measurement tool that uses lasers as a carrier to achieve ranging functions. At present, the lasers used in handheld laser rangefinders on the market are mainly the following: working wavelengths of 905 nm and 1540 nm

Points to consider when purchasing a rangefinder:

Measurement range

2. Measurement accuracy

3. occasions of use

Basically divided into the following situations:

a) It only needs to be performed within a few meters or ten meters.

The ranging accuracy of the rangefinder is also divided into nominal accuracy and actual accuracy. For nominal accuracy, and

Rangers are installed on warships to determine the target distance to determine the range of artillery and torpedoes.

DME Ranging Applications for Aircraft Aircraft

Binocular laser rangefinder

Technical Parameters

Magnification: 9 times

Field of view: 93m @ 1000m

Weight: 652 grams

Brightness: 13.0

Perspective: 5.3

Farthest range: 1371.6 meters

Nearest range: 9 meters

Power: CR2

Compass: Yes

Rainproof function: Yes

Aiming system: 13 adjustable

Outer packing: carrying case and strap

Temperature display: Yes

Tripod: Support

Ballistic calculation: support

Angle calculation: support

Unique technology: smart menu rotation