CN117784436A - Multiband laser beam combining system and beam control method - Google Patents

Abstract

The invention relates to a multiband laser beam combining system and a beam control method, wherein the multiband laser beam combining system comprises a laser beam combining module and a combined beam monitoring module, the laser beam combining module comprises a sub-beam laser, a control reflector, a beam combining mirror and a high-reflection mirror, sub-beams emitted by the sub-beam laser irradiate on the control reflector, are reflected by the control reflector to reach the beam combining mirror to be combined into a combined beam, reach the high-reflection mirror through the beam combining mirror, reflect combined laser from one side of the high-reflection mirror, and output test beams from the other side of the high-reflection mirror to enter the combined beam monitoring module. Compared with the prior art, the invention realizes the synthesis of multiple beams and is suitable for lasers with various energies or broadband; the absolute position control of each light beam is realized, and the synthesis precision is ensured through feedback adjustment; the method has the advantages of ensuring the pointing stability of the laser synthesized beam, reducing the difficulty of a subsequent laser emission system and the like.

Description

Multiband laser beam combining system and beam control method

Technical Field

The invention relates to multi-band laser beam combining, in particular to a multi-band laser beam combining system and a beam control method.

Background

With the rapid development of laser technology, lasers are increasingly used in the fields of military, medical treatment, communication and the like. In recent years, applications of high-brightness, multi-band laser systems are urgently required in many fields such as high-energy laser light sources, laser cladding, advanced manufacturing, and the like. However, the single laser is affected by heat damage, nonlinear effect, thermal lens effect, element structure, heat dissipation condition, etc., and the wavelength and power of the output laser are limited. The laser beam combining technology is one of effective methods for breaking through single-path laser output power, ensuring beam quality and realizing wide wavelength.

The laser beam combining technology is divided into two main types, namely coherent beam combining, which means that a plurality of laser beams with the same wavelength, a certain phase relation and coherence are combined into one emergent laser beam. The technology has strict requirements on the phase, the line width, the frequency and the like of the sub-beams, and the phase difference of each sub-beam is controlled to be constant, so that the technology has great difficulty, is complex in system and cannot be practically used; and the incoherent beam combination is mainly the main spectrum beam combination of the main stream, and a plurality of lasers with different wavelengths are combined into one laser output by utilizing a specific optical device. The technology has no strict requirement on parameters of the sub-beam laser, so the technology is rapidly developed.

Currently, researchers put forward a plurality of laser beam combining system design methods based on the basic principle of spectrum beam combining, one type is that no beam adjustment or monitoring measures exist, and the laser beam combining method cannot cope with beam separation caused by laser self-jitter, assembly errors, vibration, environmental temperature change and the like, so that the system beam quality and efficiency are greatly reduced, and the method is not practical. As disclosed in application publication No. CN102289078A, a first laser beam is incident on a beam combining mirror at the brewster angle, so that two laser beams are combined into one beam, and the laser beam of the laser beam is linearly polarized. The method has the problems that the random polarized laser can not be combined, because the Brewster angle has polarization requirements on the reflected light beam and the transmitted light beam, and the accurate Brewster angle can not be achieved, the reflectivity and the transmissivity of the light beam are greatly reduced, most of the energy is absorbed under the action of high energy, the beam combining lens (a film polarizer) generates high temperature rise, the synthesized light spots are seriously separated, the Brewster angle is generally the ratio of the refractive indexes of two media, the angle is large, the film plating difficulty of the lens is large, and the lens is absorbed greatly, so that the lens is not suitable for being used as the beam combining lens. The beam combining method has the advantages of less combination quantity, complex system structure, huge system and high requirement on the sub-beam laser, and the cost is increased. The method is based on controlling the synthesized light beams, monitoring the precision of the synthesized light beams, ensuring the synthesis precision of the system through adjustment, improving the quality and efficiency of the light beams, and having certain practicability. However, the precision of the direction of the combined beam cannot be controlled, the position precision of the phase combination of each sub-beam can be only realized, high requirements are put forward on a subsequent beam expansion reflection system, the selected lens is required to consider the error of random light spot irradiation to the lens caused by random light spot shaking and environmental vibration, and the emission system is required to accurately control the direction of the combined beam, so that the error of light spot shaking caused by a laser beam combination system is compensated, and the subsequent control system is more complex. For example, the paper of the new method for monitoring and adjusting the beam of the high-energy laser emission system and the research of the method for directly monitoring and correcting the emission direction of the multiband laser are all to utilize the light spot of the direct or indirect monitoring composite beam to cooperate with the active control to adjust the precision of the composite beam. The above method has the problems that when multiple beams which are overlapped enter simultaneously, light spots are overlapped together, the wavelength of each sub-beam is difficult to determine, and the angle or position value of each sub-beam cannot be calculated through an algorithm. In order to distinguish the synthesized light spot sub-beams, an electric switching optical gate or a target wheel optical filter needs to be added, so that all the wavelengths to be monitored are forced to enter the detector successively and are distinguished, but the monitoring precision is reduced, and the complexity and the stability of the system are increased. Application publication number CN114006269a discloses a high power semiconductor laser direct output system and its polarization beam combining structure, but the number of beams that can be combined in this prior art is limited.

In summary, how to combine multiple lasers and determine the angle value of each sub-beam is a technical problem to be solved.

Disclosure of Invention

The invention aims to overcome the defect that a plurality of lasers cannot be combined or the angle value of each laser beam cannot be known in the prior art, and provides a multi-band laser beam combining system and a beam control method.

The aim of the invention can be achieved by the following technical scheme:

according to one aspect of the invention, there is provided a multiband laser beam combining system, comprising a laser beam combining module and a combined beam monitoring module, wherein the laser beam combining module comprises at least two sub-beam lasers, at least two control reflectors, a beam combining mirror and a high-reflection mirror, the sub-beams emitted by the sub-beam lasers irradiate on the control reflectors, are reflected by the control reflectors to reach the beam combining mirror to be combined into a combined beam, reach the high-reflection mirror through the beam combining mirror, reflect combined laser from one side of the high-reflection mirror, and output a test beam from the other side of the high-reflection mirror to enter the combined beam monitoring module; the control reflector adjusts the angle of beam reflection, and the composite beam monitoring module monitors the position of the sub-beams.

As a preferable technical scheme, the number of the control reflectors is at least four, and the position and the angle of each sub-beam emitted by each sub-beam laser are respectively adjusted by two control reflectors; and the surface of the control reflector is plated with a high-reflection film, and the wavelength range corresponding to the high-reflection film comprises the wavelength of the reflected light beam on the surface of the control reflector.

As a preferable technical scheme, the surface of the high-reflection mirror is plated with a broadband reflection film, and the wavelength range corresponding to the broadband reflection film comprises the wavelengths of all sub-beams emitted by the sub-beam lasers.

As a preferred embodiment, the synthetic laser has an energy of at least 99.95% of the synthetic beam.

As an optimal technical scheme, the surface of the beam synthesis mirror is plated with a beam synthesis film, and the tolerance range of the plating angle of the beam synthesis film is +/-0.15 degrees.

As a preferable technical scheme, the system further comprises at least three double-sided high-reflection mirrors, wherein the surfaces of the double-sided high-reflection mirrors are plated with high-reflection films, and the two sides of the double-sided high-reflection mirrors reflect light beams injected by the sub-beam lasers or control the mirrors.

As a preferable technical scheme, the wavelength range corresponding to the high-reflection film comprises the wavelength of the light beam reflected by the surface where the high-reflection film is positioned, and the tolerance range of the film coating angle is +/-3 degrees.

As a preferable technical scheme, the installation angles of the control reflecting mirror, the light beam combining mirror, the high reflecting mirror and the double-sided high reflecting mirror are consistent.

As a preferable technical scheme, the system further comprises a collimating lens arranged at the laser output end of the sub-beam laser.

According to another aspect of the present invention, there is provided a beam control method using a multi-band laser beam combining system, further using a controller, comprising the steps of:

step S1, a sub-beam laser emits sub-beams to irradiate a control reflector;

s2, controlling the reflecting mirror to reflect the light beam to reach the light beam synthesizing mirror;

s3, synthesizing at least two light beams into a synthesized light beam by a light beam synthesizing mirror;

s4, the composite light beam reaches a high-reflection mirror, one surface of the high-reflection mirror reflects the composite laser, and the other surface outputs a test light beam to enter a composite light beam monitoring module;

and S5, the combined beam monitoring module monitors the absolute positions of all sub-beams in real time through the test beams and feeds back the absolute positions to the controller, and the controller adjusts and controls the absolute positions of the reflectors.

Compared with the prior art, the invention has the following beneficial effects:

1) The invention realizes the combination of multiple beams by the position arrangement of the sub-beam laser, the control reflector, the beam combining mirror and the high-reflection mirror, has no special requirements on the sub-beam laser and the beam combining mirror, and is suitable for the combination of lasers with various energies or broadband;

2) The invention realizes the absolute position control of each beam by controlling the pitching and the moving of the reflecting mirror, and then adjusts the feedback of the synthesized beam monitoring module to ensure the synthesis precision;

3) The tolerance range of the beam combining film coating angle on the surface of the beam combining mirror is +/-0.15 degrees, the tolerance range of the high-reflection film coating angle on the surface of the double-sided high-reflection mirror is +/-3 degrees, and the requirement of the coating tolerance is low;

4) On one hand, the beam combining precision is ensured, and the beam quality and the efficiency of a laser beam combining system are improved; on the other hand, the pointing stability of the laser synthesized beam is ensured, and the difficulty of a subsequent laser emission system is reduced.

Drawings

Fig. 1 is a schematic diagram of the overall structure of a multiband laser beam combining system according to the present invention;

FIG. 2 is a schematic diagram of the structure of the other parts of the invention except the synthesized beam monitoring module;

FIG. 3 is a schematic diagram of a beam monitoring module according to the present invention;

FIG. 4 is a schematic diagram showing the beam profile of a first sub-beam laser 1-1 according to the present invention;

FIG. 5 is a schematic diagram showing the beam profile of a second sub-beam laser 1-2 according to the present invention;

FIG. 6 is a schematic diagram showing the beam profile of a third sub-beam laser 1-3 according to the present invention;

FIG. 7 is a schematic view of the angle control of the control mirror of the present invention;

FIG. 8 is a schematic diagram of the beam combiner according to the present invention;

FIG. 9 is a schematic diagram of the present invention for controlling the mirror position and angle simultaneously;

FIG. 10 is a schematic diagram of a mirror position control function of the present invention;

the reference numerals in fig. 1 indicate:

1. the laser beam combining module 7 is used for combining the light beam monitoring module;

the reference numerals in fig. 2 indicate:

11. a first sub-beam laser, 12, a second sub-beam laser, 13, a third sub-beam laser, 21, a first collimating lens, 22, a second collimating lens, 23, a third collimating lens, 3, a double-sided high reflecting mirror, 41, a first control reflecting mirror, 42, a second control reflecting mirror, 43, a third control reflecting mirror, 5, a beam combining mirror, 61, a first high reflecting mirror, 62, a second high reflecting mirror;

the reference numerals in fig. 3 indicate:

71. absorber 72, high reflector 73, attenuation sheet 74, focusing lens 75, detector;

the reference numerals in fig. 9 indicate:

44. a first position control mirror 45, a second position control mirror 46, a third position control mirror 51, a first beam combining mirror 52, a second beam combining mirror.

Detailed Description

The following description of the embodiments of the present invention will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are some, but not all embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the present invention without making any inventive effort, shall fall within the scope of the present invention.

Example 1

As shown in fig. 1, the present invention provides a multi-band laser beam combining system comprising a laser beam combining module 1 (shown in fig. 2) and a combined beam monitoring module 7 (shown in fig. 3). The invention realizes laser beam combination without depending on the inherent design of lenses, adopts the double-sided high reflecting mirror 3, the control reflecting mirror, the beam combining mirror 5 and the high reflecting mirror to carry out configuration and surface coating according to the actual requirement of the laser beam combination, and can realize the combination of laser beams in different wave bands, laser beams in different angles and multiple laser beams. The laser beam combining module 1 comprises a sub-beam laser, a collimating lens, a double-sided high-reflection mirror 3, a control reflection mirror, a beam combining mirror 5 and a high-reflection mirror, and the system is provided with the absolute precision control and adjustment of combined beams, and can theoretically combine the beams emitted by an infinite sub-beam laser into one laser output. The laser beam combining part combines all the sub-beam lasers into one beam of laser, most of the energy is reflected and emitted through the high-reflection mirror, one point of combined beam is transmitted to be used as a test beam to be incident into the combined beam monitoring module 7, the combined beam monitoring module 7 can monitor the beam combining state in real time, the combined beam can be fed back to the control mirror of the laser beam combining part, the control mirror is controlled to perform pitching rotation, the beam is regulated and fed back, and the pointing precision of the combined beam is guaranteed.

As shown in fig. 2, the present invention exemplifies a composite three-beam, the sub-beam laser including a first sub-beam laser 11, a second sub-beam laser 12, and a third sub-beam laser 13; the collimator lens includes a first collimator lens 21, a second collimator lens 22, and a third collimator lens 23; the steering mirrors include a first steering mirror 41, a second steering mirror 42 and a third steering mirror 43.

As shown in fig. 3, the composite beam monitoring module 7 includes an absorber 71, a high reflecting mirror 72, an attenuation sheet 73, a focusing lens 74, and a detector 75, and has a function of monitoring the positions of three sub-beams of the composite beam in real time.

As shown in fig. 4, the first sub-beam laser 11 emits a first sub-beam, and the first sub-beam laser is collimated by the first collimating lens 21 to form a parallel beam or the divergence angle of the sub-beam laser is compressed to emit a small spot, and the small spot is reflected by the first control mirror 41 to the double-sided high-reflection mirror 3, reflected by the first high-reflection mirror 61, reflected again to the beam combining mirror 5, and emits laser light.

As shown in fig. 5, the second sub-beam laser 12 emits a second sub-beam, and the second sub-beam laser is collimated by the second collimator lens 22 into a parallel beam or compresses the divergence angle of the sub-beam laser to emit a small spot, and the small spot is reflected by the second control mirror 42 to the double-sided high-reflection mirror 3, reflected to the first high-reflection mirror 61, reflected again to the beam combiner 5, and emits laser light.

As shown in fig. 6, the third sub-beam laser 13 emits a third sub-beam, and the third sub-beam is collimated by the third collimator lens 23 to be a parallel beam or the divergence angle of the sub-beam laser is compressed, so that a small spot is emitted, reflected by the double-sided high-reflection mirror 3 to the third control mirror 43, reflected to the beam combining mirror 5, and emitted.

The first sub-beam and the second sub-beam are combined together through the double-sided high-reflection mirror 3, and then are combined together through the beam combining mirror 5 and the third sub-beam, and the absolute positions of the three sub-beam angles can be respectively regulated and controlled through the corresponding control reflecting mirrors, so that the combining precision is ensured.

The combined beam passes through the second high-reflection mirror 62 to reflect and output 99.95% of beam energy, the surface of the second high-reflection mirror 62 is coated with a reflecting film, the absorption of the reflecting film system is extremely small, the thermal lens effect is basically not generated, and most of energy is mainly reflected, so that the high-energy laser attenuator is suitable for attenuation of a high-energy laser. The film plated on the surface of the high-reflection mirror is a broadband reflection film, and the wavelength range corresponding to the broadband reflection film comprises the wavelengths of light beams emitted by all the sub-beam lasers. The laser light transmitting a little energy enters the composite beam monitoring module 7. The combined light beam enters the high reflector 72 to further attenuate energy, the film is removed according to the energy which can be borne by the detector 75, the safety of the detector 75 is ensured, the transmitted energy enters the attenuation sheet 73 to continue attenuation, finally, lasers with different wavelengths are focused at corresponding positions of the detector 75 through the focusing lens 74 to be the theoretical absolute positions, and then the light beams of different sub-beam lasers are controlled at the corresponding positions through adjusting the control reflector.

The installation angles of the lenses of the double-sided high-reflection lens 3 and the control reflecting mirror, the beam combining lens 5 and the high-reflection lens are consistent, the angles of the lenses are parallel, the incidence angle of laser incidence to the lenses (the included angle between the laser and the normal line of the lenses) is generally 10-45 degrees, no special angle incidence is needed, the incidence is usually designed into a small angle, on one hand, the system is small in size, simple and reliable, convenient to install, on the other hand, the lens coating efficiency is high, and the tolerance and the efficiency can be guaranteed. The surface of the double-sided high-reflection mirror 3 is plated with a high-reflection film, and both sides simultaneously reflect the beam of the sub-beam laser or control the beam reflected by the reflecting mirror. The tolerance of the coating angle of the double-sided high-reflection mirror 3 is required to be large, the tolerance is generally given to 6 degrees (namely + -3 degrees), the high reflection efficiency in the 6-degree tolerance range is 99.9% or more, the high-reflection efficiency is mainly used for being compatible with the angle deviation of the first sub-beam and the second sub-beam, and the good combination of the two laser beams under a small angle is ensured.

The sub-beam laser emits laser beams to be synthesized; the collimating lens is used for converting the sub-beam laser into parallel light to be emitted, and if the self-collimation or the divergence angle of the laser is very small, the collimating lens is not needed; the double-sided high reflection is that the two sides are plated with high reflection mirrors 72 with different film systems, the wavelength range corresponding to the high reflection film comprises the wavelength of the reflected light beam on the surface where the high reflection film is positioned, the high reflection of the sub-beams with different wavelengths is ensured, the light beam synthesis mirror 5 is replaced, the complexity of the system is reduced, the high reflection mirror is basically not absorbed, and no thermal effect exists, in the system, the high reflection film corresponding to the wavelength of the first incident laser and the second incident laser is plated at the same time, and the high reflection film corresponding to the wavelength of the third incident laser is plated at the same time; the angle of each corresponding sub-beam is regulated by the control reflector, the regulation schematic diagram is shown in fig. 7, the sub-beam laser can be ensured to be incident to the corresponding position, the reflector is generally a fast reflector or a piezoelectric regulating mirror, the absolute position of the beam can be dynamically regulated in real time by controlling the rotation and pitching of the reflector, each sub-beam can be ensured to be precisely emergent according to the required position, the control reflector is plated with a high-reflection film on both sides, the wavelength range corresponding to the high-reflection film comprises the wavelength of the reflected beam on the surface of the high-reflection film, the front surface is plated with the high-reflection film, the back surface is plated with the high-reflection film, the main function is to reflect the high-energy laser (when the composite laser is the high-energy laser) again, and the transmitted one-point energy is prevented from damaging the control device of the control reflector.

As shown in fig. 8, the beam combining mirror 5 mainly uses the wavelength selective characteristic to combine the laser beams transmitted and reflected by the sub-beams of different wavelengths into one beam, and mainly combines the transmitted laser beam of the third sub-beam laser 13 with the reflected laser beams of the first sub-beam laser 11 and the second sub-beam laser 12 into one beam, and there is no requirement for the polarization of the laser beams, as shown in fig. 6. The surface of the first high reflection mirror 61 is plated with a broadband reflection film, and the wavelength range corresponding to the broadband reflection film contains the wavelengths of the sub-beams emitted by the first sub-beam laser 11 and the second sub-beam laser 12, so that the incident laser is ensured to be reflected efficiently. The surface of the beam combining mirror is plated with a beam combining film, the beam combining film can realize transmission and reflection, the plating angle tolerance range of the beam combining film is +/-0.15 degrees, and compared with the plating angle tolerance range of the existing other beam combining systems or methods, the requirement is lower. The existing beam combination system generally has specific requirements on key devices, such as a 45-degree beam combination lens required by polarization beam combination, or the beam combination system is required to be incident at a special angle such as a Brewster angle, and the combination limit is relatively large; the beam combiner has no special requirements on the self angle setting and the incident beam angle, and can be set according to the actual system requirements.

Example 2

As shown in fig. 9, the present invention provides a multi-band laser beam combining system comprising a laser beam combining module 1 (shown in fig. 2) and a combined beam monitoring module 7 (shown in fig. 3). The laser beam combining module 1 comprises a sub-beam laser, a collimating lens, a control reflector, a position control reflector and a beam combining reflector 5, wherein the position and the angle of the laser beam combining module can be accurately controlled by adding a plurality of position control reflectors, and the mode aims at the condition that the short-distance combining requirement or the requirement on the position and the angle of the beam is met. The whole device has simple structure and convenient installation and control.

The present invention is still exemplified by a combined three-beam, the sub-beam laser comprising a first sub-beam laser 11, a second sub-beam laser 12 and a third sub-beam laser 13; the collimator lens includes a first collimator lens 21, a second collimator lens 22, and a third collimator lens 23; the control mirrors include a first control mirror 41, a second control mirror 42, and a third control mirror 43; the position control mirrors include a first position control mirror 44, a second position control mirror 45, and a third position control mirror 46; the beam combining mirror includes a first beam combining mirror 51 and a second beam combining mirror 52.

The invention controls the beam position and angle of the corresponding sub-beam laser together by adding the position control reflector and matching with the control reflector (angle). Wherein the position control mirror changes the position of the light beam incident on the angle control mirror, primarily by changing the position. The steering mirror functions in accordance with that of embodiment 1 described above. The beam combining mirror 5 has a beam combining function, combines the first sub-beam laser 11 and the second sub-beam laser 12 into one beam of laser output, and has a function of controlling the angle of the sub-beam lasers.

As shown in fig. 10, the position control mirror controls the position of the beamlets by adjusting the translation.

Example 3

The invention also provides a beam control method using the multiband laser beam combining system, which still uses three beams for example, and comprises the following steps:

the first sub-beam laser 11 emits a first sub-beam, and the first sub-beam laser is collimated into a parallel beam by the first collimating lens 21 or compresses the divergence angle of the sub-beam laser to make a small light spot emergent, and the small light spot is reflected to the double-sided high reflection mirror 3 by the first control reflector 41, reflected to the first high reflection mirror 61, reflected to the beam combining mirror 5 again and emergent laser; the second sub-beam laser 12 emits a second sub-beam, and the second sub-beam laser is collimated into a parallel beam by the second collimating lens 22 or compresses the divergence angle of the sub-beam laser to make a small light spot emergent, and the small light spot is reflected to the double-sided high-reflection mirror 3 by the second control reflector 42, reflected to the first high-reflection mirror 61, reflected to the beam combining mirror 5 again, and emergent laser; the third sub-beam laser 13 emits a third sub-beam, and the third sub-beam is collimated by the third collimating lens 23 to form a parallel beam or the divergence angle of the sub-beam laser is compressed, so that a small light spot is emitted, reflected by the double-sided high reflection mirror 3 to the third control reflection mirror 43, reflected to the beam combining mirror 5, and emitted.

The first sub-beam and the second sub-beam are combined together through the double-sided high-reflection mirror 3, and then are combined together through the beam combining mirror 5 and the third sub-beam. The combined beam passes through the second high reflection mirror 62 reflecting 99.95% of the beam energy out.

While the invention has been described with reference to certain preferred embodiments, it will be understood by those skilled in the art that various changes and substitutions of equivalents may be made and equivalents will be apparent to those skilled in the art without departing from the scope of the invention. Therefore, the protection scope of the invention is subject to the protection scope of the claims.

Claims (10)

1. The multi-band laser beam combining system is characterized by comprising a laser beam combining module (1) and a combined beam monitoring module (7), wherein the laser beam combining module (1) comprises at least two sub-beam lasers, at least two control reflectors, a beam combining mirror (5) and a high-reflection mirror, sub-beams emitted by the sub-beam lasers irradiate the control reflectors, are combined into combined beams through reflection of the control reflectors and reach the beam combining mirror (5), and reach the high-reflection mirror through the beam combining mirror (5), the combined laser is reflected from one side of the high-reflection mirror, and test beams are output from the other side of the high-reflection mirror and enter the combined beam monitoring module (7); the control reflector adjusts the angle of beam reflection, and the composite beam monitoring module (7) monitors the position of the sub-beams.

2. The multi-band laser beam combining system according to claim 1, wherein the number of the control mirrors is at least four, and each sub-beam emitted by the sub-beam laser is respectively adjusted in beam position and beam angle by two control mirrors; and the surface of the control reflector is plated with a high-reflection film, and the wavelength range corresponding to the high-reflection film comprises the wavelength of the reflected light beam on the surface of the control reflector.

3. The multi-band laser beam combining system according to claim 1, wherein the high-reflection mirror is coated with a broadband reflection film, and the wavelength range corresponding to the broadband reflection film includes wavelengths of all sub-beams emitted by the sub-beam lasers.

4. The multi-band laser beam combining system of claim 1, wherein the combined laser has an energy of at least 99.95% of the combined beam.

5. The multi-band laser beam combining system according to claim 1, wherein the beam combining mirror (5) is coated with a beam combining film, and the tolerance range of the beam combining film coating angle is + -0.15 degrees.

6. A multi-band laser beam combining system according to claim 1, further comprising a double-sided high-reflection mirror (3), wherein not less than three of the sub-beam lasers are provided, the surface of the double-sided high-reflection mirror (3) is coated with a high-reflection film, and the sub-beam lasers or the light beams incident from the control mirror are reflected simultaneously on both sides.

7. The system of claim 6, wherein the highly reflective film has a wavelength range including a wavelength of a reflected beam on a surface thereof, and the tolerance range of the film is ± 3 °.

8. The multi-band laser beam combining system according to claim 6, wherein the control mirror, the beam combining mirror (5), the high reflecting mirror and the double-sided high reflecting mirror (3) are installed at the same angle.

9. The multi-band laser beam combining system of claim 1, further comprising a collimating lens disposed at the laser output of the sub-beam laser.

10. A beam control method using the multi-band laser beam combining system of any one of claims 1 to 9, characterized by further using a controller, comprising the steps of:

step S1, a sub-beam laser emits sub-beams to irradiate a control reflector;

s2, controlling the reflecting mirror to reflect the light beam to reach the light beam synthesizing mirror (5);

s3, synthesizing at least two light beams into a synthesized light beam by a light beam synthesizing mirror (5);

s4, the composite light beam reaches a high-reflection mirror, one surface of the high-reflection mirror reflects the composite laser, and the other surface outputs a test light beam to enter a composite light beam monitoring module (7);

and S5, the combined beam monitoring module (7) monitors the absolute positions of all sub-beams in real time through the test beams and feeds back the absolute positions to the controller, and the controller adjusts and controls the absolute positions of the reflectors.