Refraction and diffraction type light field regulation and control system and method for laser cutting

Abstract

The invention discloses a refraction and diffraction type light field regulation and control system and method for laser cutting, and the system comprises a light source which is used for generating a high-power Gaussian beam; the upper protective glass is used for protecting the main light path; the collimating mirror is used for collimating the high-power Gaussian beams into parallel Gaussian beams, and the refraction and diffraction regulation and control mirror is used for converging the parallel Gaussian beams; and the lower protective glass is used for protecting the main light path. According to the refraction and diffraction type light field regulation and control system, the focusing regulation and control mirror is arranged, one face of the focusing regulation and control mirror is a refraction face, the problems that when single diffraction type regulation and control are adopted, only the focus plane is distributed in a flat-topped mode, and light beams in front of and behind the focus are partially Gaussian are solved, and flat-topped light beams are formed in the long focal depth range in front of and behind the focus; and the other surface is a diffraction surface, so that the problem that light spot distribution at the focus plane is slightly Gaussian during single refraction type regulation and control is avoided, flat-top light spot distribution is formed at the focus plane, and the cutting effect when the high-brightness laser is used for cutting a thick plate is improved.

Description

Technical Field

[0001] The present application belongs to the field of laser cutting technology, and specifically relates to a refractive-diffractive light field control system and control method for laser cutting. Background Art

[0002] As a non-contact thermal processing method, laser cutting is widely used in the automotive, shipbuilding, aviation, electronics, home building materials and other industries due to its unique non-contact, cutting speed, and cutting quality advantages. Fiber lasers combined with laser cutting heads have the advantages of fast cutting speed and precise cutting in plate cutting. As the core component of laser cutting, the traditional optical path of the laser head is mainly to collimate the laser emitted by the laser with a collimator, and then focus the focusing lens to achieve the shaping of the light beam. Therefore, the optical path of the cutting head has a crucial influence on the final cutting effect.

[0003] As the industry develops, the demand for thin plate cutting speed increases. Using high-brightness lasers with traditional optical path cutting heads can increase thin plate cutting speed, which has become an industry trend. However, because the spot of high-brightness lasers is too fine, the advantages of thick plate cutting are not obvious, and the cutting effect is not good.

[0004] In the prior art, high-brightness laser cutters cannot simultaneously meet the speed and quality requirements for thin plate cutting and thick plate cutting. Summary of the invention

[0005] The present application provides a refractive-diffractive light field control system and control method for laser cutting, which solves the problem that existing high-brightness laser cutters cannot simultaneously achieve good thin plate cutting and thick plate cutting effects, which easily leads to poor thick plate cutting quality.

[0006] The technical solution adopted in this application is:

[0007] A refractive-diffractive light field control system for laser cutting, comprising:

[0008] A light source, the light source is used to generate a high-power Gaussian beam;

[0009] Upper protective mirror, used to protect the main light path;

[0010] a collimator, the collimator being used to collimate the high-power Gaussian beam into a parallel Gaussian beam,

[0011] A refracting and diffraction regulating mirror, wherein the refracting and diffraction regulating mirror is used to converge the parallel Gaussian light beams;

[0012] Lower protective mirror, used to protect the main light path.

[0013] As a preferred embodiment, a refraction control surface and a diffraction control surface are respectively provided on two sides of the folding and diffraction control mirror, the refraction control surface faces the collimating mirror, and the diffraction control surface faces the lower protective mirror.

[0014] This solution also includes a refractive-diffractive light field control method, which is applied to the light field control system as described above, and the method includes:

[0015] (1) Set the focal length of the collimator to f 1. The focal length of the refractive-diffractive control mirror is f 2. Distance to the left side of the collimator f The position 1 is the front focus, which is on the right side of the refractive diffraction control mirror. f The position at 2 is the back focus, the numerical aperture of the incident Gaussian beam is set to NA1, and the divergence angle of the outgoing beam is set to NA2;

[0016] (2) Designing the curvature of the refractive control surface of the refractive diffraction control mirror specifically comprises the following steps:

[0017] Step 1: Determine the optical power of the refractive control surface;

[0018] Step 2: Determine the fitting central curvature of the refraction control surface;

[0019] Step 3: Determine the curvature distribution equation of the refraction control surface;

[0020] (3) Design the diffraction control surface phase of the refractive diffraction control mirror.

[0021] As a preferred embodiment, the step 1 further includes: based on the f 1. The NA1 and the NA2 determine the optical power of the refraction control surface:

[0022] According to the vertical axis magnification formula of the ideal optical system:

[0023] According to the angular magnification formula of the ideal light system:

[0024] Combining the vertical axis magnification formula of the ideal optical system with the angular magnification formula of the ideal light system, we can get f2:

[0025] According to the lens power formula: Φ=1 / f2, the refraction-controlled surface power is obtained.

[0026] As a preferred embodiment, the step 2 further includes:

[0027] According to the lens maker's formula: Get the fitting center curvature radius R1 of the refraction control surface, and the curvature

[0028] Wherein, the R2 tends to infinity.

[0029] As a preferred embodiment, the step three also includes: selecting five sampling image planes, namely, the focal plane of the refraction control surface, 15 mm in front of the focal plane, 40 mm in front of the focal plane, 15 mm behind the focal plane, and 40 mm behind the focal plane, and selecting a plurality of proportional sampling image points on each of the sampling image planes, and jointly fitting the set of equations.

[0030] As a preferred embodiment, the step three further comprises: based on the input Gaussian beam intensity distribution: The intensity distribution of the quasi-flat-top beam output at each sampling image plane and the position coordinate mapping relationship between the input and output beams of each sampling image point are obtained, and Snell's law is combined: n1sinθ1=n2sinθ2 to obtain the normal direction of each sampling image point.

[0031] As a preferred embodiment, designing the diffraction control surface phase includes:

[0032] S01: Selecting the middle intersection plane of the workpiece to be cut as the target image plane, and assigning a phase to the energy intensity of the target image plane;

[0033] S02: Take the phase and combine it with the light intensity on the output surface to form a light field function;

[0034] S03: The light field function is subjected to an inverse Fourier transform to obtain a light field distribution on a phase plane;

[0035] S04: Bring the light field distribution information into S01 to S03, and perform Fourier transform in combination with the light source intensity distribution.

[0036] Repeat S01-S04 until the mean square error and SSE are less than the specified value. ε .

[0037] As a preferred embodiment, the upper protective mirror, the collimating mirror, the refraction and diffraction regulating mirror and the lower protective mirror are coaxially arranged.

[0038] Due to the adoption of the above technical solution, the beneficial effects achieved by this application are as follows:

[0039] (1) This scheme first outputs a high-power incident light beam from the light source. The energy distribution of the incident light beam is Gaussian. After passing through the upper protective mirror, the energy distribution and divergence angle of the incident light beam remain unchanged. After passing through the collimator, the incident light beam is collimated into parallel light, that is, the divergence angle is 0, and the energy distribution is still Gaussian. After passing through the refraction control surface of the refraction and diffraction control mirror, the light beam is modulated into a long-focus depth rough flat-top beam. Then, after passing through the diffraction control surface of the refraction and diffraction control mirror, the light beam is modulated into a long-focus depth precision flat-top beam. After passing through the lower protective mirror, the light beam converges under the cutting nozzle. When cutting thick plates, inside the thick metal plate, this long-focus depth precision flat-top beam, combined with a high-brightness laser for cutting, can increase the cutting seam, unblock the gas path, and effectively increase the cutting speed. At the same time, it prevents the explosion caused by excessive concentration of central energy, thereby improving the cutting quality.

[0040] (2) The light source is located at the front focal position. After the incident light beam passes through the collimator, it will emit a parallel Gaussian beam in the same direction as the incident direction. Then the parallel Gaussian beam is incident on the refraction and diffraction control mirror. The refraction control surface and the diffraction control surface are designed by the control method in this scheme, so that during laser cutting, the incident parallel Gaussian beam is focused to the middle of the plate below the nozzle, and at the same time, a flat-top beam with a long focal depth and a relatively precise focal plane is formed inside the plate.

[0041] Using a collimating mirror and a folding and diffraction control mirror to generate a more precise flat-top beam, combined with a high-brightness laser for laser cutting, solves the problems of thick plate cutting quality and speed that are difficult to solve with high-brightness lasers. It can achieve both fast cutting of thin plates and fast and stable cutting of thick plates, realizing the full-scenario advantages of high-brightness lasers. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0043] Figure 1 A schematic diagram of the structure of a light field control system in one embodiment of the present invention;

[0044] Figure 2 This is a diagram of the energy distribution of the light spot at the focus in one embodiment of the present invention;

[0045] Figure 3 This is a diagram of the energy distribution of the light spot at the focus in another embodiment of the present invention;

[0046] Figure 4 FIG. 4 is a diagram showing the energy distribution of the light spot at the focus in yet another embodiment of the present invention.

[0047] Description of reference numerals:

[0048] 1-light source, 2-upper protective mirror, 3-collimating mirror, 4-fold diffraction control mirror, 5-lower protective mirror, 6-thick plate. DETAILED DESCRIPTION

[0049] In order to more clearly illustrate the overall concept of the present application, a detailed description is given below in an illustrative manner in conjunction with the accompanying drawings.

[0050] In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application may also be implemented in other ways different from those described herein. Therefore, the protection scope of the present application is not limited by the specific embodiments disclosed below. It should be noted that the embodiments of the present application and the features in each embodiment may be combined with each other without conflict.

[0051] In addition, in the description of the present application, it should be understood that the orientations or positional relationships indicated by the terms "top", "bottom", "inside", "outside", "axial", "radial", "circumferential", etc. are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0052] In this application, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or a communication; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0053] In the present application, unless otherwise clearly specified and limited, a first feature "above" or "below" a second feature may be that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in an appropriate manner in any one or more embodiments or examples.

[0054] like Figures 1 to 4As shown, the present application provides a refractive-diffractive light field control system for laser cutting, such as Figure 1 As shown, including the following settings:

[0055] Light source 1, light source 1 is used to generate a high-power Gaussian beam;

[0056] Upper protective mirror 2, used to protect the main light path;

[0057] Collimator 3, collimator 3 is used to collimate the high-power Gaussian beam into a parallel Gaussian beam.

[0058] A refracting and diffraction regulating mirror 4, which is used to converge the parallel Gaussian light beams;

[0059] The lower protective mirror 5 is used to protect the main light path.

[0060] The upper protective mirror 2, the collimating mirror 3, the refraction and diffraction regulating mirror 4 and the lower protective mirror 5 are coaxially arranged.

[0061] Furthermore, a refraction regulating surface and a diffraction regulating surface are respectively provided on two sides of the refracting / diffraction regulating mirror 4 , the refraction regulating surface faces the collimating mirror 3 , and the diffraction regulating surface faces the lower protective mirror 5 .

[0062] In this scheme, the light source 1 is used to generate a high-power Gaussian beam, the upper protective mirror 2 is used to protect the main optical path system to prevent dust from entering from the optical fiber interface, the collimator 3 is used to collimate the high-power Gaussian beam into a parallel Gaussian beam, the refractive diffraction light field control focusing mirror 7 is used to converge the parallel Gaussian beam and control the spot distribution at its focal plane and the beam energy distribution within the long focal depth range, the upper protective mirror 5 is used to protect the main optical path system to prevent dust from entering from the cutting nozzle, and the beam distribution in the thick metal plate is a flat-top beam, so that the spot is larger, the cutting seam is wider, the airflow is stable, and the energy distribution is uniform, which prevents local heat accumulation from forming a burst hole.

[0063] First, a high-power incident light beam is output from the light source 1, and the energy distribution of the incident light beam is Gaussian. After passing through the upper protective mirror 2, the energy distribution and divergence angle of the incident light beam remain unchanged. After passing through the collimating mirror 3, the incident light beam is collimated into parallel light, that is, the divergence angle is 0, and the energy distribution is still Gaussian. After passing through the refraction control surface of the refraction and diffraction control mirror, the light beam is modulated into a rough flat-top beam with a long focal depth. Then, after passing through the diffraction control surface of the refraction and diffraction control mirror 4, the light beam is modulated into a precision flat-top beam with a long focal depth. After passing through the lower protective mirror 5, the light beam converges under the cutting nozzle. When cutting the thick plate 6, inside the thick metal plate, the precision flat-top beam with a long focal depth is used in combination with a high-brightness laser for cutting, which can increase the cutting seam, make the gas path unobstructed, and effectively improve the cutting speed. At the same time, it prevents the explosion caused by excessive concentration of central energy, thereby improving the cutting quality.

[0064] Among them, the collimator 3 adopts a projection collimator 3, which is mainly used to collimate the incident light beam emitted by the fiber laser; at the same time, a refracting and diffraction regulating mirror 4 is set, which is mainly used to converge the collimated incident light beam and regulate the light field; based on the convergence of the light beam by the refracting and diffraction regulating mirror 4 and the shaping of the light beam near the focus, the light beam at the focus can be made to have a relatively perfect flat-top distribution, and at the same time, within 20mm before and after the focus, the light spot is a relatively rough flat-top distribution, thereby improving the cutting effect of the high-brightness laser when cutting the thick plate 6. The flat-top light distribution near the focus increases the diameter of the light spot compared to the Gaussian distribution. When used with a high-brightness laser, the slit is wider and the airflow is more stable; at the same time, overheating of the slit is avoided, and energy utilization is improved.

[0065] If a single refractive light field control system is used, that is, only refractive control is set, a relatively rough approximate flat-top light effect can be achieved within a longer focal depth range. However, this effect is not obvious for the cutting of a negative focal thick plate 6, when the focus is located inside the plate, because the flat-top shape is not obvious, resulting in the effect of using this approximate flat-top beam for cutting is not obvious.

[0066] If a single diffraction light field control system is used, that is, only a diffraction control mirror is set, a relatively ideal flat top light effect can be achieved at the focal position, but this flat top light effect is difficult to maintain before and after the focal point. Outside 2mm before and after the focal point, the light spot will basically convert back to a Gaussian beam, resulting in an insignificant effect of cutting a thick plate 6 using this approximately flat top beam.

[0067] The refractive-diffraction light field control system arranged in the present scheme is provided with a focusing control mirror, one side of which is a refractive surface, which can avoid the problem of a flat-top distribution only at the focal plane and a Gaussian light beam before and after the focus when a single diffraction light field control system is used, so that a flat-top light beam is formed within a longer focal depth range before and after the focus, thereby improving the cutting effect of a high-brightness laser when cutting a thick plate 6; the other side is a diffraction surface, which can avoid the problem of a Gaussian light spot distribution at the focal plane when a single refractive light field control system is used, so that a relatively perfect flat-top light spot distribution is formed at the focal plane, thereby improving the cutting effect of a high-brightness laser when cutting a thick plate 6.

[0068] The present application also provides a refractive-diffractive light field control method, which is applied to the above-mentioned light field control system, and the method includes:

[0069] (1) Set the focal length of collimator 3 to f 1. The focal length of the refractive diffraction control mirror 4 is f 2, to the left of the collimator 3 f The position 1 is the front focus, which is 4 to the right of the refractive diffraction control mirror. f The position at 2 is the back focus, the numerical aperture of the incident Gaussian beam is set to NA1, and the divergence angle of the outgoing beam is set to NA2;

[0070] (2) Designing the curvature of the refractive control surface of the refractive diffraction control mirror 4 specifically includes the following steps:

[0071] Step 1: Determine the optical power of the refractive control surface;

[0072] Step 2: Determine the fitting central curvature of the refraction control surface;

[0073] Step 3: Determine the curvature distribution equation of the refraction control surface;

[0074] (3) Design the diffraction control surface phase of the refractive diffraction control mirror 4.

[0075] Preferably, the light source 1 is located at the front focal position, and after the incident light beam passes through the collimator 3, a parallel Gaussian beam will be emitted in the same direction as the incident direction. Then the parallel Gaussian beam is incident on the refraction and diffraction control mirror 4, and the refraction control surface and the diffraction control surface are designed by the control method in this scheme, so that when laser cutting is performed, the incident parallel Gaussian beam is focused to the middle of the plate below the nozzle, and at the same time, a flat-top beam with a long focal depth and a more precise focal plane is formed inside the plate.

[0076] A more precise flat-top beam is generated by using a collimator 3 and a fold-diffraction control mirror 4, and laser cutting is performed in combination with a high-brightness laser, which solves the problems of cutting quality and speed of thick plates 6 that are difficult to solve with high-brightness lasers. It can achieve both fast cutting of thin plates and fast and stable cutting of thick plates 6, realizing the full-scenario advantages of high-brightness lasers.

[0077] Specifically, in order to achieve a good cutting effect, the folding diffraction control mirror can be set in the following manner:

[0078] In a preferred embodiment, step one further includes: based on f 1. NA1 and NA2 determine the optical power of the refractive control surface:

[0079] According to the vertical axis magnification formula of the ideal optical system:

[0080] According to the angular magnification formula of the ideal light system:

[0081] Combining the vertical axis magnification formula of the ideal optical system and the angular magnification formula of the ideal light system, we can get f 2,

[0082] According to the lens focal power formula: Φ = 1 / f 2. Obtain the refraction-controlled surface optical focal length.

[0083] It can be understood that the focal length of the collimator 3 is determined by the properties of the lens, which is a known quantity. At the same time, NA1 and NA2 are known quantities that can be obtained. Therefore, the vertical axis magnification formula of the ideal optical system is combined with the angular magnification formula of the ideal light system to obtain f 2. f Substitute 2 and solve for Φ.

[0084] Furthermore, step 2 also includes:

[0085] According to the lens maker's formula: Get the fitting center curvature radius R1 of the refraction control surface, and the curvature

[0086] Among them, R2 tends to infinity.

[0087] Among them, n is the refractive index of the lens. According to the material of the lens, n is an inherent parameter of the material. L is the center thickness of the lens. Since the two sides of the refractive-diffraction regulating mirror 4 are respectively the refractive regulating surface and the diffraction regulating surface, that is, the two sides are respectively provided with the refractive mirror surface and the diffraction mirror surface, the other side of the refractive mirror surface can be regarded as a plane here, and R2 tends to infinity. Substituting the Φ value obtained in step 1, the radius of curvature R1 can be obtained. The curvature and the radius of curvature are reciprocals of each other, and then the curvature K is obtained.

[0088] In a preferred embodiment, step three also includes: selecting five sampling image planes, namely, the focal plane of the refraction control surface, 15 mm in front of the focal plane, 40 mm in front of the focal plane, 15 mm behind the focal plane, and 40 mm behind the focal plane, and selecting multiple proportional sampling image points on each sampling image plane, and jointly fitting the set of equations.

[0089] It should be noted that the number of sampled image planes selected is not limited. In this embodiment, five planes are selected as sampled image planes. If the number of sampled image planes selected is too small, the data support strength may be insufficient. If the number of sampled image planes selected is too large, the calculation amount is too large and the time consumption is long. The specific number of sampled image planes selected can be determined according to actual needs.

[0090] In addition, the sampling image points are actually a part of the sampling image surface. The equal-proportion sampling image points mentioned in this solution means that the selected sampling image points occupy an equal proportion of the sampling image surface.

[0091] Furthermore, step three further includes: based on the input Gaussian beam intensity distribution: The intensity distribution of the quasi-flat-top beam output at each sampling image plane and the position coordinate mapping relationship between the input and output beams of each sampling image point are obtained. Combined with Snell's law: n1sinθ1=n2sinθ2, the normal direction of each sampling image point is obtained.

[0092] Specifically, in this step, the input Gaussian beam intensity distribution is (like Figure 2 As shown), the distribution of the flat-top beam intensity I(r) output by the five sampling image planes is (as shown Figure 3 shown):

[0093] I(r)≈I1(r <r1),

[0094] I(r)≈I2(r <r2),

[0095] I(r)≈I3(r <r3),

[0096] I(r)≈I4(r <r4),

[0097] I(r)≈I5(r <r5);

[0098] According to this energy mapping relationship, the approximate position coordinate mapping relationship between the input light beam and the output light beam can be obtained. At the same time, according to Snell's law: n1sinθ1=n2sinθ2, where n1 is the refractive index of the incident medium, n2 is the refractive index of the output medium, θ1 is the direction of the incident light beam (the angle with the normal of the refractive surface), and θ2 is the direction of the output light beam (the angle with the normal of the refractive surface).

[0099] Corresponding to each sampling image point, according to the law of conservation of energy, the energy of the input beam on the refraction control surface is equal to the energy of the output beam on the target image plane.

[0100] Σn=C1; Σn=C2; Σn=C3; Σn=C4; Σn=C5, where n is the normalized number of rays and C is a constant.

[0101] According to this beam direction mapping relationship, combined with the position coordinate mapping relationship of the input and output beams that conforms to the law of conservation of energy, the normal direction of each sampling image point of the optimal refraction control surface is obtained, and the curvature distribution equation of the refraction control surface is obtained. The curvature design of the refraction control surface is carried out based on this data.

[0102] In one embodiment, designing the diffraction control surface phase includes: according to the equal optical path principle, it can be expressed as By introducing a light field control phase unit (scale: micrometer to millimeter level) on the refractive diffraction control mirror 4 and designing the height distribution on the diffraction control surface, the modulation of the outgoing wavefront can be realized, and the wavefront phase distribution of the outgoing light can be controlled, thereby adjusting the energy distribution of the light spot on the image plane. The gradient phase can be specifically calculated according to the Huygens-Fresnel diffraction optical theory. (Paraxial Condition) and Fourier Transform x0 is the phase plane, x1 is the imaging plane, and Z is the propagation distance. The phase distribution is designed through the GS algorithm, that is, the height distribution of the tiny raised units on the diffraction control surface is calculated.

[0103] The precise flat-top beam intensity distribution output at the focal plane is: I(r) = I3(r <r3),

[0104] The specific steps are:

[0105] S01: Select the middle intersection plane of the workpiece to be cut as the target image plane, and assign a phase to the energy intensity of the target image plane;

[0106] S02: Take the phase and combine it with the light intensity on the output surface to form a light field function;

[0107] S03: The light field function is subjected to an inverse Fourier transform to obtain the light field distribution on the phase plane;

[0108] S04: Bring the light field distribution information into S01 to S03, and combine it with the intensity distribution of light source 1 to perform Fourier transform.

[0109] Repeat S01-S04 until the mean square error and SSE are less than the specified value. ε .

[0110] According to the above principles and steps, regions with different phases (corresponding to heights) are finally generated on the diffraction control surface. In S01, the energy distribution of the light spot on the target image plane is as follows: Figure 4 As shown. After the light passes through the uneven tiny protrusions on the diffraction control surface, it will produce different phases (range 0-2π). At the same time, the different angles of the tiny protrusion units will diffract the parallel incident light into the image plane and maintain energy correspondence. The spot energy uniformity can be defined as is the average energy density in the S region, E max is the maximum energy density in the S region.

[0111] In one embodiment, according to the light field control system and light field control method of the present scheme, it is calculated that the uniformity of the light spot energy at the focus before refraction control is 46.2%, the uniformity of the light spot energy at the focus after refraction control is 81.6%, and the uniformity of the light spot energy at the focus after refraction and diffraction control is 96.5%.

[0112] When the distance between the refractive control surface and the diffraction control surface is close, the light output will be disturbed by the scattering of the latter surface, making it difficult to directly serve as the input of the latter surface; if the double lenses are set to increase the distance a little, the stray light will be dispersed due to the far distance of the light path and will not cause any impact; according to the principle of shortest equal optical path and Snell's law, the scattered light path is calculated, and then the two-surface scattered light paths are designed, and the stray light scattered back by the diffraction control surface and then scattered by the refractive control surface is controlled outside the light spot area, so as to achieve stray light-free light transmission between the two control surfaces on a control mirror.

[0113] In addition, because it is set according to the law of conservation of energy, the light spot output by this optical path ensures full utilization of energy, prevents excessive energy in the middle of the light spot, and burns the machine tool blade. At the same time, it avoids overheating and explosive holes, which wastes energy. It can ensure both cutting speed and cutting effect, thereby improving the cutting efficiency of high-brightness laser cutters when cutting thick plates, so that a single high-brightness laser cutter can meet the cutting needs of different scenarios.

[0114] Under the light spot output by this optical path, when calculating the cutting speed, the following formula can be used: speed ≈ (high brightness laser power / (plate thickness*spot diameter))*plate absorption characteristic coefficient.

[0115] Anything not described in this application can be achieved by adopting or drawing on existing technologies.

[0116] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other, and each embodiment focuses on the differences from other embodiments.

[0117] The above is only an embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.

Claims

1. A refractive-diffractive light field control system for laser cutting, characterized in that: Including the following settings: A light source, the light source is used to generate a high-power Gaussian beam; Upper protective mirror, used to protect the main light path; a collimator, the collimator being used to collimate the high-power Gaussian beam into a parallel Gaussian beam, A refracting and diffraction regulating mirror, wherein the refracting and diffraction regulating mirror is used to converge the parallel Gaussian light beams; Lower protective mirror, used to protect the main light path.

2. The refractive-diffractive light field control system according to claim 1, characterized in that: A refraction regulating surface and a diffraction regulating surface are respectively arranged on two sides of the refracting and diffraction regulating mirror, the refraction regulating surface faces the collimating mirror, and the diffraction regulating surface faces the lower protective mirror.

3. A refractive-diffractive light field control method, characterized in that: Applied to the light field control system according to claim 1, the method comprises: (1) Set the focal length of the collimator to f 1. The focal length of the refractive-diffractive control mirror is f 2. Distance to the left side of the collimator f The position 1 is the front focus, which is on the right side of the refractive diffraction control mirror. f The position at 2 is the back focus, the numerical aperture of the incident Gaussian beam is set to NA1, and the divergence angle of the outgoing beam is set to NA2; (2) Designing the curvature of the refractive control surface of the refractive diffraction control mirror specifically comprises the following steps: Step 1: Determine the optical power of the refractive control surface; Step 2: Determine the fitting central curvature of the refraction control surface; Step 3: Determine the curvature distribution equation of the refraction control surface; (3) Design the diffraction control surface phase of the refractive diffraction control mirror.

4. The refractive-diffractive light field control method according to claim 3, characterized in that: The step 1 also includes: based on the f 1. The NA1 and the NA2 determine the optical power of the refraction control surface: According to the vertical axis magnification formula of the ideal optical system: According to the angular magnification formula of the ideal light system: Combining the vertical axis magnification formula of the ideal optical system with the angular magnification formula of the ideal light system, we can get f2: According to the lens power formula: Φ=1 / f2, the refraction-controlled surface power is obtained.

5. The refractive-diffractive light field control method according to claim 3, characterized in that: The step 2 also includes: According to the lens maker's formula: Get the fitting center curvature radius R1 of the refraction control surface, and the curvature Wherein, the R2 tends to infinity.

6. The refractive-diffractive light field control method according to claim 3, characterized in that: The step three also includes: selecting five sampling image planes of the refraction control surface, namely, the focal plane, 15 mm in front of the focal plane, 40 mm in front of the focal plane, 15 mm behind the focal plane, and 40 mm behind the focal plane, and selecting a plurality of proportional sampling image points on each of the sampling image planes, and jointly fitting a group of equations.

7. The refractive-diffractive light field control method according to claim 6, characterized in that: The step three further comprises: based on the input Gaussian beam intensity distribution: The intensity distribution of the quasi-flat-top beam output at each sampling image plane and the position coordinate mapping relationship between the input beam and the output beam of each sampling image point are obtained, and the normal direction of each sampling image point is obtained by combining Snell's law: n1sinθ1=n2sinθ2.

8. The refractive-diffractive light field control method according to claim 3, characterized in that: Designing the diffraction control surface phase includes: S01: Select the middle intersection plane of the workpiece to be cut as the target image plane, and assign a phase to the energy intensity of the target image plane. S02: combining the phase φ with the light intensity on the output surface to form a light field function; S03: The light field function is subjected to an inverse Fourier transform to obtain a light field distribution on a phase plane; S04: Bring the light field distribution information into S01 to S03, and perform Fourier transform in combination with the light source intensity distribution.

9. The refractive-diffractive light field control method according to claim 8, characterized in that: Repeat S01 to S04 until the mean square error and SSE are less than the specified ε.

10. The refractive-diffractive light field control system according to claim 1, characterized in that: The upper protective mirror, the collimating mirror, the refraction and diffraction regulating mirror and the lower protective mirror are coaxially arranged.

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