What is laser scanning

1、 The definition and principle of laser scanning

Laser scanning is a technology that utilizes the characteristics of laser linear propagation in space, irradiates the surface of an object with a laser beam, and obtains shape information of the object surface by measuring the time or phase difference of reflected light. Its measurement principle is similar to radar measurement or optoelectronic ranging technology.


2、 Application fields of laser scanning

Laser scanning technology can be applied in many fields. Below are a few typical application scenarios:
1. In the field of architectural surveying, such as 3D scanning and reconstruction of building facades, roofs, and overpasses, as well as deformation analysis of buildings.
2. Industrial field: such as quantitative detection and 3D reconstruction of complex structural objects such as automobiles and airplanes.
3. Cultural heritage field: such as three-dimensional digital protection and reproduction of cultural relics, ancient buildings, etc.



3、 The advantages and disadvantages of laser scanning technology

Compared to traditional measurement methods, laser scanning technology has many advantages, such as:

1. Fast measurement speed: able to scan and measure the surface of objects in a very short time.
2. High measurement accuracy: able to obtain the true shape of the object surface and achieve sub millimeter level accuracy.
3. Strong adaptability: able to measure and reconstruct objects of different shapes.
However, there are also shortcomings, such as:
1. Dependence on environment: There are high requirements for light and reflective surfaces, such as strong light exposure and low surface reflectivity, which can affect measurement results.
2. High equipment cost: Laser scanning equipment is generally more expensive.


4、 Conclusion

Laser scanning is a promising measurement technology that can be applied in many fields, and its advantages and disadvantages need to be evaluated based on actual situations.
 
Galvanometer scanning head

The galvanometer scanning head consists of mirrors installed on a freely rotatable axis. The shaft is also equipped with a magnet. Axis suspension within the coil; Electrifying the coil will cause the shaft (and reflector) to rotate.
According to the nature of the work, galvanometer scanners are usually used in pairs. Specifically, in this case, their scanning directions are at right angles to each other. This allows the laser beam to reach any point within the plane. In many applications, specialized scanning optical devices (such as flat field focusing lenses) can focus the beam on the final surface.

The galvanometer scanning heads provide operational flexibility as their movements can be controlled in real-time by computers. They can be used in pairs to generate two-dimensional vector patterns at relatively large scanning angles (usually up to ± 20 °). They can be used together with large mirrors to adapt to large beam sizes. In summary, these characteristics make them ideal choices for applications such as demonstration lamps, material marking and welding, biomedical and ophthalmic imaging, confocal microscopy analysis, and laser assisted medicine.

Multi sided scanning head

The key component of the polygonal scanning head is a polygonal component - its edges are polished and coated, similar to mirrors. This polygonal mirror is installed on the motor shaft and rotates rapidly. This allows the laser beam to quickly scan in one direction.

Like galvanometer scanning heads, polygonal scanning systems typically use specialized scanning optical devices. It is not uncommon to make these optical devices into slender strips, as the laser beam only passes through them along a narrow straight path. This greatly reduces the size and weight of the scanning system.

The multilateral scanning head performs well in applications that require high-speed unidirectional scanning. They can work at very large scanning angles (over 50 °). When two-dimensional coverage is required, they are usually combined with some form of part motion perpendicular to the scanning direction to produce grating patterns. These characteristics make them ideal choices for applications such as laser printers and LiDAR, as well as for high-speed material processing such as large-area surface treatment and thin film pattern drawing.


Acousto-optic deflector

The acousto-optic (AO) deflector is composed of a transparent material with a piezoelectric transducer attached to its side. When driven by radio frequency, piezoelectric transducers generate sound waves (pressure/density) within the crystal. This will result in a variable and periodic spatial variation in the refractive index of the material, similar to a Bragg diffraction grating. This type of grating causes the input laser beam to deflect, and the degree of deflection depends on its period. Therefore, changing the frequency of the input signal will change the deflection angle of the beam.

Due to the absence of any moving mechanical components (hence no inertia), acousto-optic deflectors can achieve much higher scanning speeds than other technologies - up to the MHz range. In addition, they can also perform "random access" scans - a function of quickly jumping from one point in the scanning field to another. However, they can only deflect the beam within a very limited range of angles - up to a few degrees. And they only offer small aperture (<2.5 mm) sizes. This makes them most suitable for specialized purposes such as laser cooling, laser tweezers, microscopy and medical imaging, as well as some plate making process applications.

In addition to these three common types of scanning heads, there are many other service specific technologies. All of these scanning heads support the vast diversity of laser scanning applications.