Optical system with adjustable light spots, diffraction optical module and laser processing equipment

Abstract

The invention discloses a light spot adjustable optical system, a diffraction optical module and laser processing equipment, and relates to the technical field of precision processing. The optical system comprises a laser, a beam expander, a diffractive optical module and a focusing module which are sequentially arranged in the light path direction, the diffractive optical module comprises at least one diffractive optical element, and the diffractive optical element is manufactured based on a geometric phase liquid crystal polymer birefringent material. The diffractive optical module is used for regulating and controlling light spot characteristic parameters corresponding to a Gaussian beam, the Gaussian beam is emitted by the laser and enters the diffractive optical module after being expanded and collimated by the beam expander, and the light spot characteristic parameters comprise a light spot distribution position and light spot energy intensity. By the adoption of the optical system, laser energy distribution can be optimized, splashing is effectively restrained, and the welding quality and the processing efficiency are improved.

Description

Technical Field

[0001] This application relates to the field of precision machining technology, and in particular to an optical system with adjustable spot size, a diffractive optical module, and laser processing equipment. Background Technology

[0002] Welding is a process that uses heat, pressure, or both to join two parts into a single unit. It includes fusion welding, pressure welding, and brazing. As a branch of fusion welding, laser welding utilizes the high energy density of lasers to locally heat materials to melting point in an instant, with the heated area being extremely small, ranging from a few micrometers to a few millimeters, enabling relatively rapid processing.

[0003] However, in laser deep penetration welding mode, the dynamic effects that usually occur cause the molten pool to move and spray, a phenomenon known as spatter, which affects the welding quality. In addition to material loss, the ejected material may also cause unnecessary spatter adhesion on the surface of the part, requiring additional treatment. Summary of the Invention

[0004] In view of the above-mentioned defects or deficiencies in the related technologies, it is desirable to provide an optical system and diffractive optical module with adjustable spot size, as well as laser processing equipment, which can optimize laser energy distribution, suppress spatter, and improve welding quality and processing efficiency.

[0005] In a first aspect, this application provides an optical system with an adjustable beam size, the optical system comprising a laser, a beam expander, a diffraction optical module, and a focusing module arranged sequentially along the optical path. The diffractive optical module includes at least one diffractive optical element, which is made of a geometric phase liquid crystal polymer birefringent material. The diffractive optical module is used to control the spot characteristic parameters corresponding to the Gaussian beam. The Gaussian beam is emitted from the laser and is expanded and collimated by the beam expander before being incident on the diffractive optical module. The spot characteristic parameters include the spot distribution position and the spot energy intensity.

[0006] Optionally, in some embodiments of this application, the diffractive optical module has a diffractive optical element, the phase structure of which is a polarization grating phase and the delay is a half-wave delay; the diffractive optical module is used to split the Gaussian beam into two.

[0007] Optionally, in some embodiments of this application, the diffractive optical module has a diffractive optical element, the phase structure of which is a polarization grating phase with a delay of 0.305 wave delay; the diffractive optical module is used to split the Gaussian beam into three.

[0008] Optionally, in some embodiments of this application, the spacing between the continuously variable beam splitting points is determined by the phase period of the diffractive optical element, wherein the phase period is... pass get, Indicates the period of the polarization grating. This represents the coordinate value along the beam splitting direction.

[0009] Optionally, in some embodiments of this application, the polarization grating period... pass get, Indicates the diffraction angle of the polarization grating. Indicates the diffraction order. Indicates the laser wavelength.

[0010] Optionally, in some embodiments of this application, the diffractive optical module has two diffractive optical elements, the phase structure of the two diffractive optical elements is a polarization grating phase with the same period, the grating lines are in the same direction, and the delay is a half-wave delay; the diffractive optical module is used to split the Gaussian beam into two, wherein the two diffractive optical elements rotate around the optical axis at the same angle and in opposite directions.

[0011] Optionally, in some embodiments of this application, the diffractive optical module has three diffractive optical elements. Among the three diffractive optical elements, the two adjacent diffractive optical elements closest to the beam expander side are waveplate structures with a retardation of one-quarter wave delay and different rotation angles around the optical axis. The phase structure of the diffractive optical element closest to the focusing module side is a polarization grating phase with a retardation of half wave delay. The diffractive optical module is used to split the Gaussian beam into three parts and control the energy intensity of the light spot.

[0012] Optionally, in some embodiments of this application, the diffractive optical module has four diffractive optical elements. The phase structure of the first and last diffractive optical elements is a polarization grating phase with the same period, the grating lines are perpendicular to each other, and the retardation is a half-wave delay. The middle two diffractive optical elements, excluding the first and last diffractive optical elements, are waveplate structures with a quarter-wave delay and different rotation angles around the optical axis. The diffractive optical module is used to split the Gaussian beam into four and control the energy intensity of the light spot.

[0013] Secondly, this application provides a diffraction optical module, wherein the diffraction optical module is any one of the diffraction optical modules described in the first aspect.

[0014] Thirdly, this application provides a laser processing apparatus, which includes the optical system described in any one of the first aspects.

[0015] As can be seen from the above technical solutions, the embodiments of this application have the following advantages: This application provides an optical system with adjustable beam spot, a diffractive optical module, and a laser processing device. By setting a diffractive optical module in the optical path, the diffractive optical module includes at least one diffractive optical element, which is made of a geometric phase liquid crystal polymer birefringent material. This allows the diffractive optical module to control the beam spot characteristic parameters corresponding to the Gaussian beam emitted from the laser and collimated by the beam expander. The beam spot characteristic parameters include the beam spot distribution position and the beam spot energy intensity. Different beam spots can correspond to different process windows, effectively suppressing spatter and improving welding quality and processing efficiency. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 A schematic diagram of the optical path of an optical system with adjustable light spot provided in an embodiment of this application; Figure 2 A simplified model schematic diagram of a unit birefringent crystal provided for an embodiment of this application; Figure 3 A schematic diagram showing an angled incident light as provided in an embodiment of this application; Figure 4 This is a schematic diagram of the optical path of a local optical system provided in an embodiment of this application; Figure 5 An embodiment provided in this application Figure 4 The corresponding light spot control result is shown in the diagram. Figure 6 This is a schematic diagram of the optical path of another local optical system provided in an embodiment of the present application; Figure 7 An embodiment provided in this application Figure 6 The corresponding light spot control result is shown in the diagram. Figure 8 A cycle provided for embodiments of this application Schematic diagram of the azimuth angle distribution of liquid crystal molecules in a downward polarization grating; Figure 9 A cycle provided for embodiments of this application Schematic diagram of the azimuth angle distribution of liquid crystal molecules in a downward polarization grating; Figure 10 This is a schematic diagram of the optical path of another local optical system provided in an embodiment of this application; Figure 11An embodiment provided in this application Figure 10 The corresponding light spot control result is shown in the diagram. Figure 12 This is a schematic diagram of the optical path of another local optical system provided in an embodiment of this application; Figure 13 An embodiment provided in this application Figure 12 The corresponding light spot control result is shown in the diagram. Figure 14 This is a schematic diagram of the optical path of another local optical system provided in an embodiment of this application; Figure 15 An embodiment provided in this application Figure 14 The corresponding light spot control result is shown in the diagram. Figure 16 Another embodiment provided in this application Figure 14 The corresponding light spot control result is shown in the diagram. Figure 17 This is a structural block diagram of a laser processing device provided in an embodiment of this application.

[0018] Figure label: 100 - Optical system, 101 - Laser, 102 - Beam expander, 103 - Diffractive optical module, 104 - Focusing module, a1, a2, a3, a4, a5, a6, a7, a8, a9, a 10 a 11 - Diffractive optical elements, 200- Laser processing equipment. Detailed Implementation

[0019] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0020] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0021] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The following examples illustrate this. Figures 1 to 17 This application provides a detailed description of the adjustable spot optical system, diffraction optical module, and laser processing equipment provided in the embodiments of this application.

[0022] Please refer to Figure 1This is a schematic diagram of the optical path of an adjustable beam optical system provided in an embodiment of this application. The optical system 100 includes a laser 101, a beam expander 102, a diffractive optical module 103, and a focusing module 104 arranged sequentially along the optical path. The focusing module 104 is used to focus the beam onto the actual processing surface, i.e., the focal plane of the focusing module 104. The Gaussian beam emitted from the laser 101 is either completely random or linearly polarized. The diffractive optical module 103 includes at least one diffractive optical element, which is manufactured based on a geometrically phased liquid crystal polymer birefringent material. The diffractive optical module 103 is used to adjust the beam characteristic parameters corresponding to the Gaussian beam. The Gaussian beam is emitted from the laser 101 and, after being expanded and collimated by the beam expander 102, is incident on the diffractive optical module 103. The beam characteristic parameters include the beam distribution position and the beam energy intensity.

[0023] It should be noted that liquid crystal molecules are birefringent crystals, and a unit birefringent crystal can be simplified to... Figure 2 The model shown has different refractive indices for polarization states along the major and minor axes, respectively. and The beam passes through a thickness of The phase changes of the polarization components along the major and minor axes of a birefringent crystal (taking a liquid crystal waveplate as an example) are respectively... and ,Right now: (1) (2) Phase difference between the two principal axes for: (3) Therefore, the thickness of the birefringent crystal can be controlled. To change the phase difference between the two principal axes .definition x direction and y The direction can be adjusted for incident light Decomposed into and The components, and the above process, can be written as a Jones matrix. form, x direction and y The simplest case is when the directions are along the minor axis and the major axis, respectively: (4) (5) Then the emitted light for: (6) Combination Figure 3 As shown, for x direction and y The direction is not along the minor and major axes, but at a certain angle. In this case, a rotation matrix is ​​introduced. Then we have: (7) When considering the optical axis and The axes can be at any angle. In this case, a coordinate rotation transformation is required on the above equation, and the Jones matrix of the waveplate can be expressed as: (8) In equation (8), This indicates the phase delay of the waveplate.

[0024] Furthermore, the Jones matrix of any single-wave plate can be expressed as: (9) A composite waveplate is an optical system composed of multiple single waveplates. In a Cartesian coordinate system, the single waveplates of a composite waveplate are all placed parallel to the XY plane. Polarized light propagates along the Z-axis (i.e., perpendicular to the XY plane). Along the direction of polarization propagation, the single waveplates are numbered sequentially as 1, 2, ... The optical axis azimuth angles are denoted as follows: , ... And the phase delay is denoted as follows: , ... Then the Jones matrix of the composite waveplate can be expressed as: (10).

[0025] In some embodiments of this application, for example Figure 4 As shown, the diffractive optical module 103 can have a diffractive optical element a1. The phase structure of this diffractive optical element a1 is a polarization grating phase of a certain period, and the retardation is a half-wave delay. In this case, the diffractive optical module 103 is used to split the Gaussian beam into two, as shown in the figure. Figure 5 As shown. For example... Figure 6 As shown, the diffractive optical module 103 can have a diffractive optical element a2. The phase structure of this diffractive optical element a2 is a polarization grating phase of a certain period, but its delay is 0.305 wave delay. In this case, the diffractive optical module 103 is used to split the Gaussian beam into three parts, as shown in the figure. Figure 7 As shown. The spacing between the continuously variable beam splitters is determined by the phase period of the diffractive optical element. pass get, Indicates the period of the polarization grating. Represents the coordinate values ​​along the beam splitting direction, for example Figure 8 The period shown is Schematic diagram of the azimuth angle distribution of liquid crystal molecules in a downward polarization grating. Figure 9 The period shown is A schematic diagram of the azimuth angle distribution of liquid crystal molecules in a downward polarization grating; the azimuth angle value is... The period of the polarization grating pass get, Indicates the diffraction angle of the polarization grating. Indicates the laser wavelength. Indicates the diffraction order, usually Take 1. Additionally, , This represents the initial beam splitter spacing, the value of which is determined based on production and actual usage requirements. This indicates the focal length of the focusing module.

[0026] For example Figure 10 As shown, the diffraction optical module 103 can also have two diffraction optical elements a3 and a4. The phase structure of these two diffraction optical elements a3 and a4 is a polarization grating phase with the same period, the grating lines are aligned, and the retardation is half-wave delay. In this case, the diffraction optical module 103 is used to split the Gaussian beam in two. The two diffraction optical elements a3 and a4 rotate around the optical axis (i.e., the Z-axis) at the same angle and in opposite directions, as shown in the figure. Figure 11 As shown, lossless beam splitting and stepless adjustment of the beam spacing between the two beams are achieved. For example... Figure 12 As shown, the diffraction optical module 103 can also have three diffraction optical elements a5, a6, and a7. Among these three diffraction optical elements a5, a6, and a7, the two adjacent diffraction optical elements a5 and a6 closest to the beam expander 102 have a waveplate structure with a quarter-wave delay and different rotation angles around the optical axis (i.e., the Z-axis), thus changing the relative angle between the azimuth angles of the two adjacent diffraction optical elements a5 and a6. Among these three diffraction optical elements a5, a6, and a7, the diffraction optical element a7 closest to the focusing module 104 has a phase structure of a polarization grating phase of a certain period and a half-wave delay. In this case, the diffraction optical module 103 is used to split the Gaussian beam into three parts and control the energy intensity of the light spot, as shown in the figure. Figure 13 As shown, this achieves stepless adjustment of the spot energy intensity for the zeroth and positive / negative first-order diffraction orders while maintaining a constant dot pitch. Similarly, the polarization grating period... Also through get.

[0027] For example Figure 14As shown, the diffraction optical module 103 may also have four diffraction optical elements a8, a9, a10 ... 10 a 11 These four diffractive optical elements a8, a9, a 10 a 11 The first diffractive optical element a8 and the last diffractive optical element a 11 The phase structure consists of polarization gratings with the same period, the grating lines are perpendicular to each other, the retardation is half-wave delay, and four diffractive optical elements a8, a9, and a... 10 a 11 Except for the first diffractive optical element a8 and the last diffractive optical element a 11 The two diffractive optical elements in the middle, a9 and a2, are in addition to the above. 10 It is a waveplate structure with a quarter-wave delay, and the rotation angles around the optical axis (i.e., the Z-axis) are different, that is, changing the two middle diffractive optical elements a9 and a2. 10 The relative angle between the azimuth angles, at which point the diffraction optical module 103 is used to split the Gaussian beam into four and adjust the energy intensity of the light spot, as shown in the figure. Figure 15 As shown, a square 2×2 beam splitting was achieved with a constant dot pitch and stepless variation in energy intensity of the two diagonal light spots. However, by changing the first diffractive optical element a8 and the last diffractive optical element a... 11 The relative angle of the grating lines can be achieved Figure 16 The rhomboid 2×2 beam splitter shown has a constant dot spacing, resulting in a stepless variation in energy intensity between the two diagonal light spots. Similarly, the polarization grating period... Also through get.

[0028] Based on the Jones matrix principle of the aforementioned composite waveplate, for example Figure 10 In the optical system shown, the Gaussian beam exits after passing through two diffractive optical elements a3 and a4. , , , Then there is, , In the above formula, , , ,as well as .

[0029] For example Figure 14 In the optical system shown, the Gaussian beam passes through four diffractive optical elements a8, a9, a10, a20, a30, a40, a50, a60, a70, a80, a90, a10 ... 10 a 11 Subsequent emitted light , , , , , Similarly, According to the Jones matrix principle of multiple liquid crystal waveplates, when the angle between the fast axes of two waveplates changes, it is equivalent to a system consisting of a phase retarder and a rotator cascaded together.

[0030] On the other hand, embodiments of this application provide a diffraction optical module, which can be used for... Figures 1 to 16 The corresponding embodiment is any one of the diffractive optical modules 103. In the embodiments of this application, the liquid crystal diffractive optical element is manufactured by optically controlled orientation, which has the advantages of high diffraction efficiency, low cost and easy manufacturing. In addition, the energy distribution uniformity is greater than 90% and the unwanted diffraction order is less than 3%.

[0031] As another aspect, embodiments of this application provide a laser processing device. Please refer to... Figure 17 This is a structural block diagram of a laser processing device provided in an embodiment of this application. The laser processing device 200 may include... Figures 1 to 16 The corresponding embodiment includes any one of the optical systems 100. Furthermore, in high-precision laser processing applications, an electric module can be used to adjust the relative angles of the diffractive optical elements for even greater precision.

[0032] It should be noted that the descriptions of the same content in this embodiment as in other embodiments can be found in the descriptions in other embodiments, and will not be repeated here.

[0033] The adjustable spot optical system, diffractive optical module, and laser processing equipment provided in this application embodiment, by setting a diffractive optical module in the optical path, the diffractive optical module includes at least one diffractive optical element, which is made of a geometric phase liquid crystal polymer birefringent material. Thus, the diffractive optical module can be used to control the spot characteristic parameters corresponding to the Gaussian beam emitted from the laser and incident after being expanded and collimated by the beam expander. The spot characteristic parameters include the spot distribution position and the spot energy intensity. Different spots can correspond to different process windows, effectively suppressing spatter and improving welding quality and processing efficiency.

[0034] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0035] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. An optical system with adjustable spot size, characterized in that The optical system (100) comprises a laser (101), a beam expander (102), a diffractive optical module (103) and a focusing module (104) arranged in sequence along an optical path direction, The diffractive optical module (103) comprises at least one diffractive optical element, the diffractive optical element is manufactured based on a geometric phase liquid crystal polymer birefringent material, the diffractive optical module (103) is used for regulating and controlling a spot characteristic parameter corresponding to a Gaussian beam, the Gaussian beam is emitted by the laser (101) and is incident on the diffractive optical module (103) after being expanded and collimated by the beam expander (102), and the spot characteristic parameter includes a spot distribution position and a spot energy intensity.

2. The optical system of claim 1, wherein The diffractive optical module (103) has one diffractive optical element, the phase structure of the one diffractive optical element is a polarization grating phase, and the retardation is half-wave retardation; the diffractive optical module (103) is used for splitting the Gaussian beam into two.

3. The optical system of claim 1, wherein The diffractive optical module (103) has one diffractive optical element, the phase structure of the one diffractive optical element is a polarization grating phase, and the retardation is 0.305-wave retardation; the diffractive optical module (103) is used for splitting the Gaussian beam into three.

4. The optical system according to any one of claims 2 to 3, characterized in that, The stepless beam splitting point distance is determined by the phase period size of the diffractive optical element, said phase period size By Obtained, denotes the polarization grating period, denotes the coordinate value in the beam splitting direction.

5. The optical system of claim 4, wherein, Polarization grating period By Obtained, Denotes the polarization grating diffraction angle, Denotes the diffraction order, Denotes the laser wavelength.

6. The optical system of claim 1, wherein The diffractive optical module (103) has two diffractive optical elements, the phase structures of the two diffractive optical elements are polarization grating phases with the same period, the grating line directions are consistent, and the retardations are half-wave retardations; the diffractive optical module (103) is used for splitting the Gaussian beam into two, wherein the rotation angles of the two diffractive optical elements around the optical axis are the same, and the rotation directions are opposite.

7. The optical system of claim 1, wherein The diffractive optical module (103) has three diffractive optical elements, the adjacent two diffractive optical elements close to the side of the beam expander (102) in the three diffractive optical elements are wave plate structures, the retardation is one-quarter wave retardation, and the rotation angles around the optical axis are different, the phase structure of the one diffractive optical element close to the side of the focusing module (104) in the three diffractive optical elements is a polarization grating phase, and the retardation is half-wave retardation; the diffractive optical module (103) is used for splitting the Gaussian beam into three and regulating the spot energy intensity.

8. The optical system of claim 1, wherein, The diffractive optical module (103) has four diffractive optical elements, the phase structures of the first diffractive optical element and the last diffractive optical element in the four diffractive optical elements are polarization grating phases with the same period, the grating line directions are perpendicular to each other, and the retardations are half-wave retardations, the middle two diffractive optical elements in the four diffractive optical elements except the first diffractive optical element and the last diffractive optical element are wave plate structures, the retardation is one-quarter wave retardation, and the rotation angles around the optical axis are different; the diffractive optical module (103) is used for splitting the Gaussian beam into four and regulating the spot energy intensity.

9. A diffractive optical module, characterized by The diffractive optical module is the diffractive optical module (103) in any one of claims 1 to 8.

10. A laser processing apparatus characterized by comprising: The laser processing equipment (200) comprises the optical system (100) in any one of claims 1 to 8.

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