Do You Know the Optical Principle in the Handheld Welding Head?

Handheld laser welding equipment is an epoch-making star product in the laser application market in recent years.

It has rapidly emerged as one of the growth points of the green laser industry.

Since 2018, the annual compound growth of laser handheld welding has exceeded 100%.

It is expected that there will be 100 manufacturers of laser handheld welding machines in 2020 and 500 manufacturers of various types of handheld laser equipment integration in 2021, showing explosive growth.

For hand-held laser welding machine, the welding head connecting the use scene and outputting laser energy is an extremely important component.

In the welded head, the optical part is a very important part.

The basic optical principle of handheld welding head includes three parts: beam collimation, beam swing and beam focusing, as shown in the figure below.

basic optical principle of handheld welding head

After the laser beam is emitted from QBH, it becomes parallel light through the collimating mirror, then reflects to the focusing lens through the galvanometer, and finally focuses on the workpiece surface.

Beam collimation

The light from the optical fiber of QBH is a point light source with a certain divergence angle.

It will spread forward in a conical shape in the process of propagation, such as turning on a flashlight and lighting a match in the dark.

The function of the collimator is to turn the divergent light into parallel light and make it propagate along a straight line without deviation;

At the same time, the waist radius of the beam is controlled to limit it to the narrow optical path of the welding head.

Beam collimation

Beam swing

In hand-held welding, the purpose of beam swing is to improve the adaptability of weld gap.

Because the focused spot is a small light spot, it is difficult to walk along the weld track when holding it. On the other hand, it is also difficult to cover the weld with large gap.

By arranging the beam into a straight line as wide as 3.0mm, it is convenient for the operator to align and cover the laser to the weld.

Its realization is that the vibrating lens deflects back and forth at high speed driven by the motor, so as to change the laser beam path.

The basic principle is shown in the figure below:

Beam swing basic principle

According to the basic reflection law, the reflection angle is equal to the incident angle.

When the galvanometer is at angle 1, the light is reflected along path 1 and focused to point 1;

When the galvanometer is at angle 2, the light is reflected along path 2 and focused to point 2.

If the galvanometer deflects back and forth between 1 and 2 angles, the focused light spot will move between 1 and 2 points.

When the moving speed is fast enough, it can be regarded as a straight line.

The length of this straight line is called “swing width”, and the speed of deflection speed is called “swing frequency”.

swing frequency

The intelligent air-cooled handheld welder has an adjustable swing width of 0 ~ 5mm and an adjustable swing frequency of 0 ~ 300Hz.

Beam focusing

Reflected from the galvanometer is a beam of parallel light, which converges into a small spot after passing through the focusing lens, and finally incident on the workpiece surface.

The function of the focusing lens is to concentrate parallel beams together to form a small light spot, so as to produce super energy density.

Beam focusing

Role of protective lenses

In the process of hand-held welding, a certain amount of smoke and dust will be generated, which may damage the focusing lens.

Therefore, it is necessary to protect the lens to play the role of isolation and protection.


Protective lenses are consumables. Check whether they are in good condition every certain time. The service cycle is determined according to the service intensity and scene of the equipment.

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