What is laser?
Laser (Light Amplification by Stimulated Emission of Radiation), stands for "light amplification by stimulated emission of radiation". It's a bit of a mouthful and hard to understand, so let's start by looking at the following diagram:
Spontaneous radiation refers to the process where an atom at a higher energy level spontaneously transitions to a lower energy level, emitting a photon in the process. In layman's terms, it can be understood as follows: imagine a ball at its most stable position on the ground. When this ball is pushed into the air by an external force (known as pumping), and the moment the external force disappears, the ball falls from the air and releases a certain amount of energy. If this ball represents a specific atom, then during its transition, the atom will emit a photon of a specific wavelength.
The Birth of the Laser Device
In 1960, Theodore Maiman of Hughes Research Laboratories in the United States developed the first ruby laser, emitting red laser light at 694.3nm, which is widely recognized as the world's first laser device.
The laser wavelength emitted by Maiman's laser device was 694.3nm, which falls within the visible light spectrum, hence the visible red color of the laser beam. In subsequent research and development, scientists invented lasers with different wavelengths. Currently, the most common laser wavelength is 1064nm, which falls outside the visible light spectrum and is therefore not visible to the human eye.
Classification of Lasers
After grasping the principle of laser generation, people began to develop different forms of lasers. If classified according to the laser working medium, they can be divided into gas lasers, solid-state lasers, semiconductor lasers, etc.
- Classification of gas lasers includes atomic, molecular, and ionic lasers. The working medium of gas lasers is gas or metal vapor, characterized by a wide range of laser output wavelengths. The most common type is the CO2 laser, where CO2 serves as the working medium and generates 10.6um infrared laser through electrical discharge excitation.
Due to the bulky size of gas lasers resulting from their gaseous working medium, and the long wavelengths they emit, which are not ideal for material processing, gas lasers were quickly phased out of the market. They are now only used in specific areas, such as laser marking on certain plastic parts.
- Classification of solid-state lasers: ruby, Nd:YAG, etc.
Solid-state lasers use materials like ruby, neodymium-doped glass, and yttrium aluminum garnet (YAG) as their active medium. These lasers are created by uniformly doping a small amount of ions, known as activator ions, into the crystal or glass matrix of the host material. Solid-state lasers consist of an active medium, a pumping system, a resonant cavity, and cooling and filtering systems.
In the image below, the black square in the middle represents the laser crystal, which appears to be a light-colored transparent piece of glass. It is composed of a transparent crystal doped with rare-earth metals. It is the unique atomic structure of these rare-earth metals that allows for population inversion (imagine many balls on the ground being pushed into the air) when exposed to light. When the particles undergo transition and emit photons, and when there are enough photons, laser light is formed. To ensure that the emitted laser light is directed in one direction, a total reflection mirror (left lens) and a semi-reflective output mirror (right lens) are used. After the laser light is emitted, it undergoes certain optical designs to form laser energy.
The following image depicts a typical YAG fiber-optic laser transmission device. In the picture, the gray part is the laser crystal rod doped with Nd ions. It is irradiated by a red xenon lamp to generate laser light. After the laser is coupled into the fiber for transmission, it reaches the surface of the workpiece.
Due to the certain amount of wear and tear on the xenon lamp that emits laser light, similar to how fluorescent lights at home can break down after a period of use, improvements have been made to the laser illuminated by fluorescent lights. If the fluorescent lamp is replaced with a semiconductor that emits photons through internal electron transitions, the lifespan of the laser will be significantly extended. Improvements to the YAG solid-state laser have been made in two aspects: on the one hand, the xenon lamp (consumable) that excites the laser has been replaced with a semiconductor (photodiode); on the other hand, the laser crystal rod has been modified to directly dope rare earth ions into the fiber. As a result, a bulky solid-state laser has been integrated into a small laser generator. After integration, this type of laser is called a fiber laser.
When it comes to semiconductor lasers, they can be simply understood as a photodiode. Inside the diode, there is a PN junction. When a certain current is applied, electron transitions occur within the semiconductor, releasing photons and thus generating laser light.
When the laser energy released by the semiconductor is relatively small, low-power semiconductor devices can be used as the pump source (excitation source) for fiber lasers, thus forming a fiber laser.
If the power of the semiconductor laser is further increased to a level where it can be directly output to process materials, it becomes a direct semiconductor laser. Currently, direct semiconductor lasers on the market have reached the 10,000-watt level.
In addition to the aforementioned lasers, people have also invented liquid lasers, also known as fuel lasers. Compared to solid lasers, liquid lasers are more complex in terms of volume and working materials, and are rarely used.
The Principle of Laser Rangefinders
In addition to using lasers for material processing in industry, other fields such as aerospace and military are constantly developing laser applications. The use of lasers in aviation and military applications is constantly increasing, and the main laser application in this field is laser ranging. The principle of laser ranging is that distance equals speed multiplied by time. Since the speed of light is fixed, and the propagation time of light can be detected by a detection device, the distance to the object being measured can be calculated.
Schematic diagram is as follows:
What are the applications of laser rangefinders?
Laser rangefinders are widely used in aerospace. Apollo 15 took a special piece of equipment to the moon during its lunar landing mission - a large corner reflector, which was used to reflect the laser beam emitted from the Earth. By recording the round-trip time, the distance between the Earth and the Moon can be calculated. Meanwhile, laser rangefinders are also used in other aerospace fields:
- Military applications of laser rangefinders:
Many photoelectric search and tracking systems on fighter jets and land combat equipment are equipped with laser rangefinders, which can accurately determine the distance to the enemy and make corresponding defensive preparations. Among them, some land combat weapons, such as land combat rifles, are equipped with laser rangefinders to know the distance between the enemy and ourselves. With the application of laser rangefinders in the military, people are constantly studying laser weapon reconnaissance systems.
Among them, an infrared camera can be used to observe the laser beam, track the light source based on the laser beam, and locate the laser beam, as shown in the situation of the laser source observed by the infrared camera:
-
Application of Laser Rangefinding in Terrain Surveying and Mapping
Laser rangefinders used in terrain surveying and mapping are commonly known as laser altimeters, which are primarily mounted on aircraft or satellites to measure elevation data. For example, the "Chang'e-1" and "Chang'e-2" laser altimeters were key payloads of the lunar exploration satellites, tasked with obtaining three-dimensional elevation data of the lunar surface. The "Chang'e-1" satellite was launched in 2007, while the "Chang'e-2" satellite was launched in 2010. By combining elevation data with images from a CCD stereo camera, the basic landforms of the lunar surface were obtained, structural units were delineated, and a preliminary geological and structural outline map of the Moon was compiled. In addition to elevation data, the "Chang'e-2" laser altimeter also acquired lunar surface reflectance information, providing reference data for subsequent soft landings. -
Application of Laser Rangefinding in Autonomous Landing of Spacecraft
Using unmanned probes to land on the surfaces of target celestial bodies such as the Moon, Mars, or asteroids for field exploration and even sample return is an important avenue for human exploration of the universe and a hotspot in the development of future deep space exploration activities. Launching satellites or probes for soft landings on other planetary surfaces is a crucial direction in space exploration. -
Application of Laser Rangefinding in Autonomous Space Rendezvous and Docking
Autonomous space rendezvous and docking is an extremely complex and precise process. The rendezvous process refers to two or more spacecraft meeting at a predetermined position and time in space orbit, with a working distance of 100km to 10m. This process requires GPS guidance, microwave radar, lidar, and optical imaging sensors for measurement. Space docking refers to the mechanical connection of two spacecraft after they meet in space orbit, with a working distance of 10m to 0m. This process primarily relies on advanced video guidance sensors (AVGS).
- Application of Laser Rangefinding in Space Debris Detection
Space debris detection is currently one of the important application areas of deep space laser detection technology. The United States and Russia, which have been conducting space activities for a long time, account for more than 90% of the total space debris generated. No one can count the exact number of space debris. Currently, humans can only track and monitor debris with a diameter of 10 centimeters or more. There are currently more than 17,000 such debris, and only the United States and Russia in the world have the ability to monitor them all. The National Aeronautics and Space Administration (NASA) has assigned a number to each debris. It is estimated that there are tens of millions to hundreds of millions of debris smaller than 1 centimeter, and spacecraft can no longer avoid colliding with them. They can only respond by strengthening their own protective capabilities. In order to safely and sustainably develop and utilize space resources, it is necessary to continuously improve the tracking and monitoring technology for space debris, enhance the ability to analyze and predict the space debris environment, and seek effective measures to control space debris.
Development Direction of Laser Rangefinders
Currently, laser rangefinders are developing towards smaller size, higher precision, and longer measurement distances. Among them, the mainstream laser rangefinder manufacturers on the market include Keyence and Leica.
ERDI has been at the forefront of the world in the field of 1535nm laser rangefinders. Adhering to the values of military defense and human peace, the company has adopted self-developed 1535nm erbium glass laser technology to manufacture 1535nm erbium glass lasers and produce a 1535nm series of laser rangefinder modules. These modules are safe for human eyes, with a ranging capability of 1 to 35 kilometers, high precision, stable performance, low power consumption, small size, and compact structure. They allow for 107 light emissions and have a long service life, providing excellent laser ranging solutions for drones, airborne, and other optoelectronic platforms. They are equipped with UART (TTL_3.3V), RS232, and RS422 communication electrical interfaces (choose one of the three). With built-in host computer software, instruction set, and communication protocol, it is convenient for users to carry out secondary development. Below are some basic parameters of several models,For more 1535nm laser rangefinder products, please visit https://erdicn.com/collections/1535nm-laser-rangefinder-module.
|
LRF Specs |
LRF00308C |
LRF0612C |
LRF0815C |
LRF1017C |
LRF1221C |
LRF1830C |
|
|
Extended Range (km) |
4.2 |
7.1 |
20 |
20 |
25 |
30 |
|
|
Range to NATO Vehicle (2.3 × 2.3m) |
Single Measurement (km) |
3.5 |
6 |
8 |
10 |
12 |
18 |
|
Continuous (10Hz) (km) |
3.5 |
6 |
8 |
10 |
12 |
18 |
|
|
Human (.5 x 1.8m) single Measurement (nm) |
2 |
3.8 |
4 |
5 |
6 |
9 |
|
|
Human (.5 x 1.8m) continous (10Hz) (nm) |
2 |
3.8 |
4 |
5 |
6 |
9 |
|
|
Wavelength (nm) |
1535±1 |
1535±1 |
1535±5 |
1535±5 |
1535±5 |
1535±5 |
|
|
Single Measurement Time（s) |
≤0.03 |
≤0.03 |
≤0.5 |
≤0.5 |
≤0.5 |
≤0.5 |
|
|
Continuous Measurement(1, 4, 10, 20, 100, 200, 500 Hz) |
1~10(Adjustable) |
1~10(Adjustable) |
1~10(Adjustable) |
1~10(Adjustable) |
1~10(Adjustable) |
1~10(Adjustable) |
|
|
Precision (cm) |
±100 |
±100 |
200 |
200 |
200 |
200 |
|
|
False Detection Rate (%) |
≤1% |
≤1% |
≤1% |
≤1% |
≤1% |
≤1% |
|
|
Beam Divergence (Hrz × Vrt) (mrad) |
~0.6 |
~0.3 |
≤0.35 |
≤0.35 |
≤0.3 |
≤0.3 |
|
|
Target Distinction (m) |
20 |
50 |
30 |
30 |
30 |
30 |
|
|
Range Gating Resolution (m) |
1 |
1 |
0.1 |
0.1 |
0.1 |
0.1 |
|
|
Alignment Laser (yes/no) |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
|
|
Laser Class |
Class1 |
Class1 |
Class1 |
Class1 |
Class1 |
Class1 |
|
|
Power Consumption (W） |
≤2w |
≤4w |
2W |
2W |
2.5W |
3W |
|
|
Lifetime MTBF with assumtions |
≥1500h |
≥1500h |
1×106Number of launches |
1×106Number of launches |
1×106Number of launches |
1×106Number of launches |
|
|
Serial Interface |
Uart（TTL_3.3V） |
Uart（TTL_3.3V） |
422/TTL |
422/TTL |
422/TTL |
422/TTL |
|
|
Operating Temperature |
-40~70℃ |
-40~70℃ |
-40℃-＋65℃ |
-40℃-＋65℃ |
-40℃-＋65℃ |
-40℃-＋65℃ |
|
|
Dimensions （mm) |
≤48×31×25 |
≤65×48×32 |
≤80×64×42 |
≤107×62×72 |
≤115×60×62 |
≤125×100×70 |
|
|
Weight (g) |
≤32±1 |
≤58±1 |
≤180 |
≤280 |
≤350 |
≤410 |
|
Notes:
- Target size 2.3 x 2.3 m, visibility 25 km, maximum measuring time,target reflectivity 30%, detection probability 90%.
- At 6 km range setting. At 12 km range setting measuring time is 0.5- 2.4 seconds
- Range performance depends on applied rate.
- Depending on distance and target reflectivity.
- Depending on received signal level. Up to three (3) targets: First, Second and Las *6) Power consumption < 1.8 W selectable with 85 % range performance.
- Power consumption <2 W selectable with 85 % range performance.
- Class 1 / Class 1M.
- In CMM 10 Hz range performance to NATO target 7300 / 13500 m
SMM= Single Measurement Mode
CMM = Continuous Measurement Mode
Summary:
Known as the "fastest blade" and the "most precise ruler," lasers will be applied in various aspects of people's lives and will find extensive applications in aviation and military fields. Lasers are both a tool and a weapon. It is important that we all use them peacefully, striving for world peace.
![Exploring the World's Longest Distance Rangefinders [120KM]](http://erdicn.com/cdn/shop/articles/erdi-1570-120.webp?v=1711097200&width=1)
