The relationship between the laser output light, beam expander, galvanometer and field lens in laser marking machine

 On the relationship between the four, many people can not, including a part of the equipment company engineers, many are waiting until the equipment problems to ask me, and customers to explain the relationship between the four a few hundred times, I think I need to spend a little time writing these out, and later when you ask, I will send this article directly to everyone.

1. Laser outgoing light (Output beam diameter), this should be good to understand, it is from the laser output spot how big. This beam is generally collimated light, note that I said collimated light, not that parallel light, many people think that the light from the laser is parallel light. We often say that the laser's outgoing beam is a few millimeters, let's say the coherent CO2 C30A laser's outgoing light is generally 1.8 ± 0.2mm, and pulsed fiber laser outgoing light is generally 7mm, these are said to be the size of the laser's outgoing light. The continuous fiber laser out of the light is a point light source, is not out of the spot size of the statement, as we usually see incandescent light bulbs, is a point light source, there is no way to say out of the spot size. Only out of the collimated light laser, we say the laser's emitted light. If we look at the parameters of the laser table, there is a parameter called output beam diameter (mm), or called: 1/e², is said to be this parameter.

 

2. Beam expander (beam expander), as the name suggests, the beam expander is to expands the laser beam of an optical device. The laser beam waist radius and the product of the divergence angle is a fixed value. A laser beam after X times the beam expander, the beam waist radius increases by X times, but the beam divergence angle is reduced to the original 1 / X. Some people ask: what are the benefits of reducing the divergence angle? Tell you, the divergence angle of the laser beam, through the same specifications of the focusing mirror, the focus point will be smaller. But for the role of beam expanding mirror, many customers do not understand deeply, and not many can say clearly. I will briefly say here: 

 

First: make the focusing effect better, and get a smaller focus spot. Remember, the larger the magnification of the beam expander out of the light by the focusing mirror effect is better. Second: so that the energy is evenly dispersed, so that the energy density to reach the galvanometer lens or reflector is reduced, so that the galvanometer lens or 45-degree reflector lens is more durable. Third: amplify the beam, this is mainly embodied in the laser show system, although we are in the industrial processing system, each time to amplify the beam, our purpose is not only to amplify the beam but the first two purposes and laser show system with beam expanding mirrors is to amplify the purpose of the beam.

 

In our marking machine, the role of the beam expander is mainly a few: 1, compression of the divergence angle, 2, expansion of the beam, so that the incident beam into the field mirror becomes larger (which can make the focusing spot finer), 3, so that the laser can be more uniformly dispersed into the vibration lens so that the vibration lens is more durable.

 

3. Galvanometer (galvanometer), in the final analysis, is two ammeters + pointer tied X\Y lens, and we say the number of galvanometer spots (10 spots 12 spots 20 spots, etc.) is the area of the vibration lens to reflect how much of the beam. The smaller the galvanometer lens, the smaller the beam that can be reflected; the larger the galvanometer lens, the larger the beam that can be reflected. However, we should note that the larger the lens of the galvanometer, the greater the weight of the lens of the galvanometer, the greater the weight of the movement of things, the greater the inertia, the greater the inertia will inevitably lead to the speed of the galvanometer can not be fast up. Why choose a large vibrating lens? It is because in order to get a smaller divergence angle of the beam, will use a large multiplier beam expander, and the use of a large multiplier beam expander, then it will inevitably come out of the large beam, the large beam must be the corresponding vibration lens to reflect. That is to say, the smaller the spot of the vibrating lens, the better the speed up, the larger the spot of the vibrating lens, and the speed is bound to be slower, but it can make the incident light bigger, can play a better-focusing spot purpose. In short, remember one thing: line fineness and marking speed are a contradiction in terms, we can only go according to the need for trade-offs, and can not both seek the best.

 

4. Field mirror (scan lens), to put it simply is a focusing mirror, to put it more complexly is in its focal position in a prescribed plane of each point is a focusing point of the lens, of course, this statement is not rigorous, but basically this is the meaning. Field lens has a parameter, called the incident pupil (Full Beam Diameter), also known as the pupil. For the pupil, we require the pupil of the field lens ≥ the spot of the galvanometer, if the pupil of the field lens is smaller than the spot of the galvanometer, then there may be, a marking to the edge of the field lens, the edge will be marked significantly shallower than the middle of the position, and even appear to be able to hit the range will be smaller than the nominal range of the field lens.

 

Above has talked about some basic things, now begin to talk about the relationship between the four.

 

Laser outgoing light x times the beam expander mirror ≤ spot number of the galvanometer ≤ field mirror pupil, in the pursuit of speed, we try to make the spot number of the galvanometer a little smaller. In the pursuit of precision, we require that the spot number of the galvanometer and the pupil of the field mirror should be larger.

 

Example description:  

 

1. If a customer requests a CO2 laser marking machine to do assembly line marking, just ask to play on the production date and batch number, the line thicker does not matter much, the choice of laser for the new sharp Vi30, then we generally recommend: choose 3 times the CO2 beam expanding mirror, 10 spot vibration mirror, the ordinary 14 pupil of the CO2 field lens can be.

 

2. If the customer is still using the new Vi30 laser, the requirements of marking are a little fine, then I recommend using 4 times the CO2 beam expander, 12 spot galvanometer, and regular 14 pupils of the CO2 field lens.

 

3. If the customer with a hot spiked V2 type glass tube to do flight marking machine, the requirements of fast, we choose 2 times the beam expanding mirror, 10 spot galvanometer, and ordinary 14 pupil of the CO2 field lens.

 

4. If the customer with a thermal spiked V2 type glass tube requirements for fine marking, we can give the customer with 4 times the beam expander, 20 spot galvanometer, and special 20 pupils of the CO2 field mirror (this field mirror is generally imported, field lens is generally in the 60mm or so), if this precision is not enough, then we recommend that customers use: 6 times the CO2 beam expander + 30 spots CO2 galvanometer + 30 pupil of the CO2 field mirror (Note: the CO2 field lens can be used to mark the glass tube.). If this precision is not enough, then we suggest customers use: 6 times CO2 beam expander + 30 spot CO2 galvanometer + 30-pupil CO2 field mirror (Note: This kind of field mirror is imported, and the lenses are generally 75mm).

 

5. If the customer with 200 watts of pulsed fiber laser to do deep engraving, taking into account the vibrating lens can not withstand too high energy density, and deep engraving on the speed will not be too high, we can recommend that customers use 2 times the quartz beam expander, the laser's outgoing light beam expansion, and then use the 14 spot or 15 spot fiber optic vibrating lens. Of course, the field mirror should also use quartz, the pupil in 14mm or more. Or if you use the 10-pupil quartz field lens, we must artificially avoid the full-width marking, let's say 150 * 150 of the 10-pupil quartz field lens, but the vibrating mirror over the light is 14 spots, then the marking should be selected within the width of 110 * 110, or there will be a weak edge of the phenomenon of light.

 

6. If the customer is ready to do 500 watts pulsed fiber laser marking machine, to do some deep engraving, the laser 500 watts pulsed, is equivalent to 5000 watts of continuous laser, so we must consider the vibration mirror and the field mirror's ability to withstand, so you generally need to choose 3.5-4 times the water-cooled quartz beam expander + 30mm spot water-cooled vibration mirror (vibration mirror lens need to choose the quartz) + 30 into the water-cooled quartz field mirror. quartz field lens.