Fast axis numerical aperture adjusting device of BAR strip laser

Abstract

The invention relates to a fast-axis numerical aperture adjusting device of a BAR strip laser, and belongs to the technical field of 3D printing, the fast-axis numerical aperture adjusting device comprises the BAR strip laser and a fast-axis numerical aperture adjusting unit arranged on a light path of the BAR strip laser, the fast-axis numerical aperture adjusting unit is a meniscus cylindrical mirror or two cylindrical mirrors, by controlling the thickness of the meniscus cylindrical mirror and the curvature of the incident plane and the emergent plane or adjusting the distance and the focal length of the two cylindrical mirrors, the divergence angle of the laser emitted by the BAR strip laser in the fast axis direction is compressed, and meanwhile, the virtual image of the fast axis light-emitting point of the laser penetrating through the fast axis numerical aperture adjusting unit is controlled to coincide with the actual light-emitting point, so that the real light-emitting point of the laser is adjusted. The printing precision is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of 3D printing, and particularly relates to a device for adjusting the fast-axis numerical aperture of a BAR bar laser. Background Art

[0002] For laser processing, such as laser cutting, drilling, laser welding, laser marking, and laser 3D printing, the commonly adopted method is that a single-spot laser beam scans an image horizontally or by a galvanometer mirror reflection on a two-dimensional working plane or a curved surface. This method usually uses a fiber laser as the light source. After collimating the emitted laser, it is finally focused into a small spot at the working surface through an imaging system for processing and printing. Currently, in laser processing, especially in the field of 3D printing, due to only one laser spot, the processing and printing efficiency is low, which has become the biggest bottleneck restricting its development.

[0003] With the continuous improvement of semiconductor laser technology, semiconductor lasers have been widely used in civilian fields such as laser processing, medical treatment, and optical fiber communication, as well as military fields such as laser guidance, laser communication, and laser weapons, due to their advantages such as small volume, high electro-optical conversion efficiency, high coupling efficiency, and fast response speed. Semiconductor lasers have many advantages such as small volume, light weight, and high efficiency. As the application fields have higher and higher requirements for laser power, high-power semiconductor laser devices packaged in BAR bar arrays have emerged and developed rapidly.

[0004] Currently, a BAR bar array-packaged laser usually has dozens of light-emitting units, and can achieve a laser power output of up to several hundred watts. For example, for a typical 808nm BAR bar laser, the spacing between each light-emitting unit is 0.5mm, the fast and slow axis dimensions of the light-emitting surface of the laser resonator are 1*150um, 19 light-emitting units are in a group, and the power of the entire laser is about 100W. Patent CN111092364A gives a typical window structure of a BAR bar laser. The laser beam of each light-emitting point of the BAR bar laser is divided into a slow axis and a fast axis. The slow axis divergence angle is about 6 - 25°, and the fast axis divergence angle is 20 - 70°. Usually, the divergence angle of the fast axis is more than 3 times that of the slow axis, as Figure 1 shown. Different divergence angles of the fast and slow axes mean that the numerical apertures of the lenses in the subsequent optical path system are also different. In order to allow the laser to pass through the optical lens and focus and image, the numerical aperture of the optical lens must be designed according to the fast axis. A too large numerical aperture of the fast axis not only makes the diameter of the lens thicker, but also makes the optical structure of the lens more complex in order to correct the geometric aberration of the focused imaging of the large numerical aperture. Therefore, a method is needed to compress the fast-axis numerical aperture so that it matches the slow-axis numerical aperture, thereby simplifying the size and structure of the optical imaging system.

[0005] The most typical method for compressing the fast-axis numerical aperture is as Figure 2As shown, using a cylindrical lens in the fast axis direction can reduce the divergence angle of the fast axis beam and make its divergence angle the same as that of the slow axis through appropriate parameters. Using this method to compress the divergence angle of the fast axis beam will have a consequence that the virtual image position of the fast axis divergence light spot will move backward. For the entire imaging system, the object distances of the fast axis and the slow axis are different, and finally the focusing imaging positions of the fast axis and the slow axis at the imaging end are also different. Therefore, a clear imaging light spot cannot be formed, and for 3D printing, the printing accuracy is relatively low. Summary of the Invention

[0006] The purpose of the present invention is to provide a device for adjusting the fast axis numerical aperture of a BAR bar laser to solve the problem that the object distances of the fast axis and the slow axis are different and a clear imaging light spot cannot be formed due to the backward movement of the virtual image position of the fast axis divergence light spot when compressing the divergence angle of the fast axis beam in the existing structure.

[0007] To achieve the above purpose, the technical solution of the present invention is as follows: The present invention relates to a device for adjusting the fast axis numerical aperture of a BAR bar laser, which includes a BAR bar laser and a fast axis numerical aperture adjusting unit arranged on the optical path of the BAR bar laser. The fast axis numerical aperture adjusting unit is used to compress the divergence angle of the laser emitted by the BAR bar laser in the fast axis direction and make the virtual image of the fast axis light emitting point of the laser passing through the fast axis numerical aperture adjusting unit coincide with the actual light emitting point.

[0008] Preferably, the fast axis numerical aperture adjusting unit is a meniscus cylindrical lens. The incident surface and the exit surface of the meniscus cylindrical lens both protrude towards the BAR bar laser, and the radius of curvature of the incident surface and the exit surface are R 1 and R 2 respectively, and the thickness of the meniscus cylindrical lens is H ; the calculation method of the radius of curvature R 1 of the incident surface of the meniscus cylindrical lens, the radius of curvature R 2 of the exit surface, and the thickness H of the meniscus cylindrical lens is as follows: Set four auxiliary parameters h , θ , K , γ , and let: , , , , Among them, L is the distance between the light emitting point of the BAR bar laser and the meniscus cylindrical lens, βis the original divergence angle in the fast axis direction of the laser emitted by the BAR bar laser, n is the refractive index of the meniscus cylindrical lens; At the same time, establish the following three equations: , , ; Among them, β’ is the divergence angle in the fast axis direction after being adjusted by the fast axis numerical aperture adjustment unit, m is the scaling factor; Substitute the four auxiliary parameters into the three equations to calculate the curvature of the incident surface of the meniscus cylindrical lens R 1. The curvature of the exit surface R 2 and the thickness H .

[0009] Preferably, the fast axis numerical aperture adjustment unit includes a first cylindrical lens and a second cylindrical lens, and the focal lengths of the first cylindrical lens and the second cylindrical lens are respectively f 1 and f 2, and the distance between the first cylindrical lens and the second cylindrical lens is L 2; The focal lengths of the first cylindrical lens and the second cylindrical lens f 1, f 2 and the distance between the first cylindrical lens and the second cylindrical lens L 2 are calculated as follows: Set two auxiliary parameters V and k , and let: , , Among them, L 1 is the distance between the light emitting point of the BAR bar laser and the first cylindrical lens, β is the original divergence angle in the fast axis direction of the laser emitted by the BAR bar laser; At the same time, establish the following three equations: , , , Among them, β’ is the divergence angle in the fast axis direction after being adjusted by the fast axis numerical aperture adjustment unit, m is the scaling factor; Substitute the two auxiliary parameters into the three equations to calculate the focal length of the first cylindrical lens f 1, the focal length of the second cylindrical lensf 2. The distance between the first cylindrical lens and the second cylindrical lens is L 2.

[0010] Preferably, the divergence angle in the fast axis direction after being adjusted by the fast axis numerical aperture adjusting unit β’ satisfies: β’=mβ = α , where α is the original divergence angle in the short axis direction of the laser emitted by the BAR bar laser.

[0011] Adopting the technical solution provided by the present invention, compared with the prior art, it has the following beneficial effects: The fast axis numerical aperture adjusting device of the BAR bar laser involved in the present invention compresses the divergence angle in the fast axis direction of the laser emitted by the BAR bar laser through a meniscus cylindrical lens or two ordinary cylindrical lenses. By controlling the thickness of the meniscus cylindrical lens and the curvature of the incident surface and the exit surface, or adjusting the distance and focal length between the two cylindrical lenses, the virtual image of the fast axis light emitting point of the laser passing through the fast axis numerical aperture adjusting unit coincides with the actual light emitting point, so that the object distances of the fast axis and the slow axis are different, forming a clear imaging light spot to improve the printing accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 is a schematic structural diagram of a laser encapsulated in a BAR bar array.

[0013] Figure 2 is a schematic diagram of a typical compression of the fast axis numerical aperture; Figure 3 is a schematic diagram of the fast axis numerical aperture adjusting device of the BAR bar laser involved in Embodiment 1; Figure 4 is a schematic diagram of the fast axis numerical aperture adjusting device of the BAR bar laser involved in Embodiment 2.

[0014] Reference numerals: 1 - BAR bar laser, 2 - meniscus cylindrical lens, 3 - first cylindrical lens, 4 - second cylindrical lens. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0015] To further understand the content of the present invention, the present invention will be described in detail in combination with embodiments. The following embodiments are used to illustrate the present invention, but are not used to limit the scope of the present invention.

[0016] Embodiment 1: Refer to the attached Figure 3As shown in the figure, a fast-axis numerical aperture adjustment device for a BAR bar laser according to this embodiment includes a BAR bar laser 1 and a fast-axis numerical aperture adjustment unit disposed on the optical path of the BAR bar laser 1. The fast-axis numerical aperture adjustment unit in this embodiment is a meniscus cylindrical lens 2. The incident surface and the exit surface of the meniscus cylindrical lens 2 both protrude toward the BAR bar laser, and the radii of curvature of the incident surface and the exit surface are R 1 and R 2 respectively, and the thickness of the meniscus cylindrical lens 2 is H ; The radius of curvature of the incident surface of the meniscus cylindrical lens 2 R 1, the radius of curvature of the exit surface R 2, and the thickness of the meniscus cylindrical lens H are calculated as follows: Since the relational expressions of the parameters of this structure are relatively complex, therefore, four auxiliary parameters h , θ , K , γ are first set in this embodiment. Let: , , , , wherein, L is the distance between the light-emitting point of the BAR bar laser and the meniscus cylindrical lens, β is the original divergence angle of the laser emitted by the BAR bar laser in the fast-axis direction, n is the refractive index of the meniscus cylindrical lens 2; At the same time, the following three equations are established: , , ; wherein, β’ is the divergence angle in the fast-axis direction after being adjusted by the fast-axis numerical aperture adjustment unit, m is the scaling factor. In different optical systems, β’ requirements are different. Therefore, the scaling factor m is set according to different requirements. Usually, it is required that the divergence angle after fast-axis compression is the same as the divergence angle of the slow axis, that is, β’=mβ = α , α is the original divergence angle of the laser emitted by the BAR bar laser in the short-axis direction; By substituting four auxiliary parameters into three equations, the curvature of the incident surface of the meniscus cylindrical lens can be calculated for all cases. R 1. The curvature of the exit surface R 2 and the thickness H ; When the meniscus cylindrical lens 2 satisfies the above parameters, it can ensure that the virtual image of the fast-axis light-emitting point of the laser after passing through the fast-axis numerical aperture adjustment unit coincides with the actual light-emitting point, without affecting the subsequent co-focusing imaging with the slow axis.

[0017] Example 2: Referring to the attached Figure 4 As shown, a fast-axis numerical aperture adjustment device for a BAR bar laser according to this example includes a BAR bar laser 1 and a fast-axis numerical aperture adjustment unit disposed on the optical path of the BAR bar laser 1. The fast-axis numerical aperture adjustment unit in this example includes a first cylindrical lens 3 and a second cylindrical lens 4, and the focal lengths of the first cylindrical lens 3 and the second cylindrical lens 4 are respectively f 1 and f 2, and the distance between the first cylindrical lens 3 and the second cylindrical lens 4 is L 2. The focal lengths f 1, f 2 of the first cylindrical lens 3 and the second cylindrical lens 4, and the distance L 2 between the first cylindrical lens 3 and the second cylindrical lens 4 are calculated as follows: Since the relational expressions of the parameters of this structure are relatively complex, therefore, this example first sets two auxiliary parameters V and k , and let: , , where L 1 is the distance between the light-emitting point of the BAR bar laser 1 and the first cylindrical lens 2, β is the original divergence angle of the laser emitted by the BAR bar laser 1 in the fast-axis direction; At the same time, the following three equations are established: , , , where β’ is the divergence angle in the fast-axis direction after being adjusted by the fast-axis numerical aperture adjustment unit, m is the scaling factor; By substituting the two auxiliary parameters into the three equations, calculate the focal length f 1 of the first cylindrical lens 3, the focal length f 2 of the second cylindrical lens 4, and the distance between the first cylindrical lens 3 and the second cylindrical lens 4 is L 2; When the first cylindrical lens 3 and the second cylindrical lens 4 satisfy the above parameters, it can be ensured that the virtual image of the fast-axis light-emitting point of the laser after passing through the fast-axis numerical aperture adjustment unit coincides with the actual light-emitting point, without affecting the subsequent co-focusing imaging with the slow axis.

[0018] It should be noted that the fast-axis numerical aperture adjustment device of the BAR bar laser in the above two solutions can not only be used to reduce the divergence angle in the fast-axis direction of the laser, but also to increase it.

[0019] The present invention has been described in detail above in conjunction with the embodiments, but the above content is only the preferred embodiment of the present invention and cannot be considered as limiting the scope of implementation of the present invention. All equivalent changes and improvements made according to the scope of the present invention application should still fall within the scope covered by the patent of the present invention.

Claims

1. A fast axis numerical aperture adjustment device for a BAR laser, characterized in that: It includes a BAR bar laser and a fast axis numerical aperture adjustment unit arranged on the optical path of the BAR bar laser. The fast axis numerical aperture adjustment unit is used to compress the divergence angle of the fast axis direction of the laser emitted by the BAR bar laser, and at the same time make the virtual image of the fast axis light-emitting point of the laser after passing through the fast axis numerical aperture adjustment unit coincide with the actual light-emitting point.

2. The fast axis numerical aperture adjustment device of the BAR laser according to claim 1, characterized in that: The fast axis numerical aperture adjustment unit is a meniscus cylindrical mirror, the incident surface and the exit surface of the meniscus cylindrical mirror are both convex toward the BAR laser bar direction, and the curvature radius of the incident surface and the exit surface are respectively R 1 and R 2. The thickness of the meniscus cylindrical mirror is H ; Curvature radius of incident surface of meniscus cylindrical mirror R 1. Curvature radius of the output surface R 2 and the thickness of the meniscus mirror H The calculation method is: Set four auxiliary parameters h , θ , K , γ ,make: ， ， ， ， in, L is the distance between the BAR laser light source and the meniscus cylindrical mirror, β is the original divergence angle of the fast axis of the laser emitted by the BAR laser, n is the refractive index of the meniscus cylindrical mirror; At the same time, the following three equations are established: ， ， ； in, β’ is the divergence angle in the fast axis direction after adjustment by the fast axis numerical aperture adjustment unit, m is the scaling factor; Substituting the four auxiliary parameters into the three equations, the curvature of the incident surface of the meniscus cylindrical mirror is calculated: R 1. Curvature of the output surface R 2 and thickness H .

3. The fast axis numerical aperture adjustment device of the BAR laser according to claim 1, characterized in that: The fast axis numerical aperture adjustment unit comprises a first cylindrical mirror and a second cylindrical mirror, and the focal lengths of the first cylindrical mirror and the second cylindrical mirror are respectively f 1 and f 2. The distance between the first cylindrical mirror and the second cylindrical mirror is L 2; The focal lengths of the first cylindrical mirror and the second cylindrical mirror f 1. f 2 and the distance between the first cylindrical mirror and the second cylindrical mirror L 2 is calculated as: Set two auxiliary parameters V and k ,make: ， ， in, L 1 is the distance between the BAR laser light emitting point and the first cylindrical mirror, β is the original divergence angle of the fast axis direction of the laser emitted by the BAR laser; At the same time, the following three equations are established: ， ， ， in, β’ is the divergence angle in the fast axis direction after adjustment by the fast axis numerical aperture adjustment unit, m is the scaling factor; Substituting the two auxiliary parameters into the three equations, we can calculate the focal length of the first cylindrical lens. f 1. Focal length of the second cylindrical lens f 2. The distance between the first cylindrical mirror and the second cylindrical mirror is L 2.

4. The fast axis numerical aperture adjustment device of the BAR strip laser according to claim 2 or 3, characterized in that: The divergence angle in the fast axis direction after being adjusted by the fast axis numerical aperture adjustment unit β’ satisfy: β’=mβ = α ， in, α is the original divergence angle of the laser light emitted by the BAR laser in the short axis direction.

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