Telecentric flat field lens

Abstract

The application discloses a kind of telecentric flat-field lenses.The telecentric flat-field lens includes diaphragm, first lens, second lens, third lens and fourth lens sequentially arranged along optical axis from object plane to image plane;The radius of curvature of the object side of the first lens is R11, and the radius of curvature of the object-image side of the first lens is R12;The radius of curvature of the object side of the second lens is R21, and the radius of curvature of the object-image side of the second lens is R22;The radius of curvature of the object side of the third lens is R31, and the radius of curvature of the object-image side of the third lens is R32;The radius of curvature of the object side of the fourth lens is R41, and the radius of curvature of the object-image side of the fourth lens is R42;Wherein:-29mm≤R11≤-25mm, 1450mm≤R12≤1650mm;-85mm≤R21≤-65mm, 55mm≤R22≤-38mm;1150mm≤R31≤1350mm, -80mm≤R32≤-60mm;200mm≤R41≤225mm, -136mm≤R42≤-116mm.Make it can be used with existing galvanometer lens, and then obtain good cutting effect, meet the use demand.

Description

Technical Field

[0001] This invention relates to the field of optical lens technology, and more particularly to a telecentric plan lens. Background Technology

[0002] As laser power increases, galvanometer lenses are no longer limited to marking and welding; more and more companies are starting to use galvanometer lenses combined with flat-field lenses for cutting thin plates. Traditional field lenses have poor telecentricity, resulting in a certain slope at the edges of the cut plates, requiring further processing to meet application requirements. Therefore, to solve the above problems, a new type of telecentric lens needs to be developed. Summary of the Invention

[0003] This invention provides a telecentric flat field lens to ensure good cutting results during laser processing and meet processing requirements.

[0004] In a first aspect, an embodiment of the present invention provides a telecentric plan lens, comprising an aperture stop, a first lens, a second lens, a third lens, and a fourth lens arranged sequentially along the optical axis from the object plane to the image plane;

[0005] The object-side surface of the first lens has a radius of curvature of R11, and the image-side surface of the first lens has a radius of curvature of R12; the object-side surface of the second lens has a radius of curvature of R21, and the image-side surface of the second lens has a radius of curvature of R22; the object-side surface of the third lens has a radius of curvature of R31, and the image-side surface of the third lens has a radius of curvature of R32; the object-side surface of the fourth lens has a radius of curvature of R41, and the image-side surface of the fourth lens has a radius of curvature of R42.

[0006] Where: -29mm≤R11≤-25mm, 1450mm≤R12≤1650mm; -85mm≤R21≤-65mm, 55mm≤R22≤-38mm; 1150mm≤R31≤1350mm, -80mm≤R32≤-60mm; 200mm≤R41≤225mm, -136mm≤R42≤-116mm.

[0007] Optionally, the distance on the optical axis from the image-side surface of the first lens to the object-side surface of the second lens is L1, the distance on the optical axis from the image-side surface of the second lens to the object-side surface of the third lens is L2, the distance on the optical axis from the image-side surface of the third lens to the object-side surface of the fourth lens is L3, and the distance on the optical axis from the image-side surface of the fourth lens to the image plane is L4, where L1 = 5.331 ± 5% mm, L2 = 0.494 ± 5% mm, L3 = 0.5 ± 5% mm, and L4 = 145.626 ± 5% mm.

[0008] Optionally, the center thickness of the first lens on the optical axis is d1, the center thickness of the second lens on the optical axis is d2, the center thickness of the third lens on the optical axis is d3, and the center thickness of the fourth lens on the optical axis is d4, wherein: 3.5mm≤d1≤4.5mm; 15.5mm≤d2≤16.5mm; 18.5mm≤d3≤20.5mm; 18.5mm≤d4≤20.5mm.

[0009] Optionally, the aperture of the aperture stop is S1, and the distance between the aperture stop and the object side of the first lens on the optical axis is L5, where S1 = 14 mm and L5 = 40 mm.

[0010] Optionally, the first lens, the second lens, the third lens, and the fourth lens are all made of fused silica glass.

[0011] Optionally, the first lens, the second lens, the third lens, and the fourth lens all have the same refractive index and Abbe number.

[0012] Optionally, the refractive index of the lens is Nd, and the Abbe number of the lens is Vd; where Nd = 1.64 ± 5% and Vd = 67.821 ± 5%.

[0013] Optionally, the focal length of the telecentric plan lens is f, and the entrance pupil diameter of the telecentric plan lens is EPD, wherein 95mm < f < 105mm, and 13mm < EPD < 15mm.

[0014] Optionally, the incident beam wavelength of the telecentric plan lens is 1064 nm.

[0015] Secondly, embodiments of the present invention provide a laser processing apparatus, including the telecentric planar lens described in any one of the first aspects.

[0016] The technical solution of this invention provides a telecentric plan lens comprising an aperture stop, a first lens, a second lens, a third lens, and a fourth lens arranged sequentially along the optical axis from the object plane to the image plane; the object-side surface of the first lens has a radius of curvature of R11, and the object-image-side surface of the first lens has a radius of curvature of R12; the object-side surface of the second lens has a radius of curvature of R21, and the object-image-side surface of the second lens has a radius of curvature of R22; the object-side surface of the third lens has a radius of curvature of R31, and the object-image-side surface of the third lens has a radius of curvature of R32. The radius of curvature of the object-side surface of the fourth lens is R41, and the radius of curvature of the image-side surface of the fourth lens is R42; where: -29mm≤R11≤-25mm, 1450mm≤R12≤1650mm; -85mm≤R21≤-65mm, 55mm≤R22≤-38mm; 1150mm≤R31≤1350mm, -80mm≤R32≤-60mm; 200mm≤R41≤225mm, -136mm≤R42≤-116mm. This allows it to be used in conjunction with existing galvanometer lenses to achieve good cutting results and meet usage requirements.

[0017] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the structure of a telecentric plan lens provided in an embodiment of the present invention;

[0020] Figure 2 This is a schematic diagram of another telecentric plan lens provided in an embodiment of the present invention;

[0021] Figure 3 A dot plot of a telecentric planar lens provided in an embodiment of the present invention;

[0022] Figure 4 A field curvature distortion diagram of a telecentric planar lens provided in an embodiment of the present invention;

[0023] Figure 5 A laser processing device is provided as an embodiment of the present invention. Detailed Implementation

[0024] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0025] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0026] Figure 1 This is a schematic diagram of the structure of a telecentric plan lens provided in an embodiment of the present invention. Figure 2 This is a schematic diagram of another telecentric plan lens provided in an embodiment of the present invention, as shown below. Figure 1 and Figure 2 As shown, the telecentric plan lens 100 includes an aperture stop S, a first lens 101, a second lens 102, a third lens 103, and a fourth lens 104 arranged sequentially along the optical axis from the object plane 10 to the image plane 20. The object-side radius of curvature of the first lens 101 is R11, and the image-side radius of curvature of the first lens 101 is R12. The object-side radius of curvature of the second lens 102 is R21, and the image-side radius of curvature of the second lens 102 is R22. The object-side radius of curvature of the third lens 103 is R31, and the image-side radius of curvature of the third lens 103 is R31. The radius of curvature is R32; the radius of curvature of the object side of the fourth lens 104 is R41, and the radius of curvature of the image side of the fourth lens 104 is R42; where: -29mm≤R11≤-25mm, 1450mm≤R12≤1650mm; -85mm≤R21≤-65mm, 55mm≤R22≤-38mm; 1150mm≤R31≤1350mm, -80mm≤R32≤-60mm; 200mm≤R41≤225mm, -136mm≤R42≤-116mm.

[0027] The telecentric plan lens 100 includes an aperture stop S, a first lens 101, a second lens 102, a third lens 103, and a fourth lens 104 arranged sequentially along the optical axis from the object plane 10 to the image plane 20. Incident light rays, after passing through the aperture stop S, can propagate along the first lens 101 to the fourth lens 104. The aperture stop S can adjust the propagation direction of the light beam and adjust the incident angle, which is beneficial for improving image quality. The surface of the lens adjacent to the object plane 10 is called the object-side surface, and the surface of the lens adjacent to the image plane 20 is called the image-side surface. The first lens 101 is a biconcave lens, with both its object-side and image-side surfaces convex towards the object plane 10. The second lens 102 is a meniscus lens, with the meniscus direction opposite to the direction of light propagation; both its object-side and image-side surfaces convex towards the image plane 20. The third lens 103 is a biconvex lens, with both its object-side and image-side surfaces convex towards the object plane 10 and image-side surfaces. The fourth lens 104 is also a biconvex lens, with both its object-side and image-side surfaces convex towards the object plane 10 and image-side surfaces. The first lens 101 and the second lens 102 are negative power lenses, possessing a beam-expanding effect. The third lens 103 and the fourth lens 104 are positive power lenses with converging properties. Simultaneously controlling the radius of curvature of each surface from the first lens 101 to the fourth lens 104 allows for sequential imaging onto the imaging plane via the first lens 101, second lens 102, third lens 103, and fourth lens 104 for processing. Furthermore, the imaging process through these lenses effectively corrects astigmatism and distortion, improving processing accuracy. The specific values ​​of the radius of curvature for each surface can be selected based on actual design requirements; this invention does not impose specific limitations. A filter is also provided along the object plane 10 to the image plane 20, located on the image-side side of the fourth lens. By providing a filter on the image-side side of the fourth lens 104, unwanted stray light can be filtered out, thereby improving the image quality of the telecentric plan lens 100.

[0028] The embodiments of the present invention employ an aperture, a first lens, a second lens, a third lens, and a fourth lens arranged sequentially along the optical axis from the object plane to the image plane, and reasonably setting the curvature radii of each surface in the first, second, third, and fourth lenses. This ensures that the incident light rays pass through the first lens to the fourth lens in sequence, achieving a good imaging effect. Consequently, this ensures that the telecentric plan lens meets the usage requirements and improves processing accuracy when used in conjunction with a galvanometer lens.

[0029] Optionally, the distance on the optical axis from the image side of the first lens 101 to the object side of the second lens 102 is L1, the distance on the optical axis from the image side of the second lens 102 to the object side of the third lens 103 is L2, the distance on the optical axis from the image side of the third lens 103 to the object side of the fourth lens 104 is L3, and the distance on the optical axis from the image side of the fourth lens 104 to the image plane 20 is L4, where L1 = 5.331 ± 5% mm, L2 = 0.494 ± 5% mm, L3 = 0.5 ± 5% mm, and L4 = 145.626 ± 5% mm. By reasonably setting the spacing between adjacent lenses, as exemplified in the figure with L1=5.331mm, L2=0.494mm, L3=0.5mm, and L4=145.626mm forming a telecentric flat field lens 100, the field curvature generated by the front lens and the field curvature generated by the rear lens in the telecentric flat field lens 100 can be balanced, so that the telecentric flat field lens 100 has a reasonable field curvature.

[0030] Optionally, the center thickness of the first lens 101 along the optical axis is d1, the center thickness of the second lens 102 along the optical axis is d2, the center thickness of the third lens 103 along the optical axis is d3, and the center thickness of the fourth lens 104 along the optical axis is d4, wherein: 3.5mm≤d1≤4.5mm; 15.5mm≤d2≤16.5mm; 18.5mm≤d3≤20.5mm; 18.5mm≤d4≤20.5mm. Reasonably setting the center thickness of the first lens 101, second lens 102, third lens 103, and fourth lens 104 helps to achieve a uniform distribution of lens sizes, ensures assembly stability, reduces aberrations in the entire telecentric plan lens 100, and shortens the overall length of the telecentric plan lens 100.

[0031] Optionally, the aperture of the aperture stop S is S1, and the distance from the aperture stop S to the object side surface of the first lens 101 on the optical axis is L5, where S1=14mm; L5=40mm.

[0032] Based on the characteristics of the telecentric optical path, the aperture stop S is positioned on the side of the first lens 101 away from the image plane 20. The aperture diameter S1 of the aperture stop S is set to 14mm, resulting in high light transmission. The distance L5 between the aperture stop S and the object side surface of the first lens 101 on the optical axis is set to 40mm. This allows for adjustment of the size of the telecentric plan lens 100, enabling lens miniaturization, improving lens resolution, and ensuring the optimal processing and use of the telecentric plan lens 100 in conjunction with a galvanometer lens.

[0033] Optionally, the first lens 101, the second lens 102, the third lens 103, and the fourth lens 104 are all made of fused silica glass, which gives each lens good thermal stability. This, in turn, enables the telecentric plan lens 100 to have good high-temperature resistance, allowing it to function normally in both high and low temperature environments. Furthermore, since the incident beam wavelength of the telecentric plan lens 100 is 1064nm, it can be applied to infrared lasers, thereby obtaining a finely focused diffuse spot.

[0034] Optionally, the first lens 101, the second lens 102, the third lens 103, and the fourth lens 104 all have the same refractive index and Abbe number. The first lens 101 has a refractive index Nd1 = 1.64 ± 5% and an Abbe number Vd1 = 67.821 ± 5%; the second lens 102 has a refractive index Nd2 = 1.64 ± 5% and an Abbe number Vd2 = 67.821 ± 5%; the third lens 103 has a refractive index Nd3 = 1.64 ± 5% and an Abbe number Vd3 = 67.821 ± 5%; and the fourth lens 104 has a refractive index Nd4 = 1.64 ± 5% and an Abbe number Vd4 = 67.821 ± 5%.

[0035] The refractive index is the ratio of the speed of light in a vacuum to the speed of light in the medium, primarily used to describe a material's ability to refract light; different materials have different refractive indices. The Abbe number is an index used to represent the dispersion ability of a transparent medium; the more severe the dispersion, the smaller the Abbe number; conversely, the less severe the dispersion, the larger the Abbe number. Thus, by appropriately setting the refractive index and Abbe number of each lens in the telecentric plan lens 100, it is beneficial to achieve a higher pixel resolution for the telecentric plan lens 100. The specific values ​​of the refractive index and Abbe number of each lens can be selected according to actual design requirements; this embodiment of the invention does not impose specific limitations.

[0036] Optionally, the focal length of the telecentric plan lens 100 is f, and the entrance pupil diameter of the telecentric plan lens 100 is EPD, wherein 95mm < f < 105mm, and 13mm < EPD < 15mm.

[0037] The exemplary telecentric plan lens 100 has a focal length f of 100mm. By appropriately setting the focal length, the total optical length of the telecentric plan lens 100 can be effectively controlled, while ensuring that the field of view is within 20°. This results in a telecentricity of less than 0.5°, guaranteeing good processing accuracy during use. Furthermore, when used with a galvanometer lens, the telecentric plan lens 100 can cut thin plates to a diameter of 51mm x 51mm. The entrance pupil diameter (EPD) of the telecentric plan lens 100 is 14mm. Appropriately setting the entrance pupil diameter ensures sufficient light transmission per unit time, guaranteeing image quality and thus good processing accuracy during use. Moreover, a suitable focal length f and entrance pupil diameter (EPD) effectively increase the image energy density on the imaging plane, thereby improving cutting accuracy and ensuring optimal performance.

[0038] Figure 3 A dot plot of a telecentric plan lens provided in an embodiment of the present invention, such as... Figure 3 As shown, the dot plot is one of the most commonly used evaluation methods in modern optical design. A dot plot refers to the phenomenon where many rays emitted from a single light source, after passing through an optical system, intersect with the image plane 20 at a point due to aberrations, forming a diffuse pattern scattered over a certain area. For example... Figure 3 As shown, the telecentric plan lens 100 provided in this embodiment of the invention exhibits relatively concentrated and uniformly distributed dispersion patterns for laser light with a wavelength of 1.064 μm across various fields of view, without any significant vertical separation of the dispersion pattern across different fields of view. Furthermore, the root mean square radius (RMS radius) values ​​for the 1.064 μm wavelength at various field-of-view positions of the telecentric plan lens 100 are 9.498 mm, 14.222 mm, 20.726 mm, 23.818 mm, and 25.166 mm, respectively, indicating that the RMS radius for each field of view is less than 25 μm. This demonstrates that the telecentric plan lens 100 exhibits low chromatic aberration and aberrations across the entire field of view, while also minimizing the impact on beam quality after focusing, making it suitable for various laser processing applications.

[0039] Figure 4 A field curvature distortion diagram of a telecentric plan lens provided in an embodiment of the present invention, such as... Figure 4 As shown, in the coordinate system on the left, the horizontal coordinate represents the magnitude of the field curvature, in mm; the vertical coordinate represents the normalized image height, which has no unit; where T represents the meridion and S represents the arc loss; from Figure 4 As can be seen, the telecentric flat-field lens 100 provided in this embodiment, with a wavelength of 1.064 μm, reflects the degree of curvature of the laser processing focusing surface under different fields of view through field curvature. Figure 4 As can be seen, the maximum field curvature of this lens is less than 0.322mm at a field of view of 1.0. Field curvature is effectively controlled, meaning that the difference in image quality between the center and the periphery is small during imaging. In the coordinate system on the right, the horizontal axis represents the magnitude of distortion in percentage; the vertical axis represents the normalized image height, which has no unit. To achieve good processing results with a telecentric plan lens 100, F-Theta distortion needs to be controlled. Figure 4 As can be seen, the maximum F-Theta distortion is less than 1%. The distortion of the telecentric flat field lens 100 provided in this embodiment has been well corrected, and the imaging distortion is small, which meets the requirements of low distortion.

[0040] Figure 5 A laser processing device provided in an embodiment of the present invention, such as Figure 5 As shown, the laser processing equipment 200 includes the telecentric planar lens 100 described in any of the above embodiments. The laser processing equipment 200 can be a laser drilling machine, a laser marking machine, or a laser cutting machine.

[0041] It should be noted that since the laser processing equipment 200 provided in this embodiment includes any of the telecentric flat field lenses 100 provided in the embodiments of the present invention, it has the same or corresponding beneficial effects as the telecentric flat field lens 100, which will not be elaborated here.

[0042] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A telecentric plan lens, characterized in that, It includes an aperture stop, a first lens, a second lens, a third lens, and a fourth lens arranged sequentially along the optical axis from the object plane to the image plane; The first lens is a biconcave negative power lens, with an object-side radius of curvature of R11 and an image-side radius of curvature of R12; the second lens is a meniscus negative power lens with the meniscus direction opposite to the light propagation direction, with an object-side radius of curvature of R21 and an image-side radius of curvature of R22; the third lens is a biconvex positive power lens, with an object-side radius of curvature of R31 and an image-side radius of curvature of R32; the fourth lens is a biconvex positive power lens, with an object-side radius of curvature of R41 and an image-side radius of curvature of R42. Where: -29mm≤R11≤-25mm, 1450mm≤R12≤1650mm; -85mm≤R21≤-65mm, -55mm≤R22≤-38mm; 1150mm≤R31≤1350mm, -80mm≤R32≤-60mm; 200mm≤R41≤225mm, -136mm≤R42≤-116mm; The incident beam wavelength of the telecentric plan lens is 1064 nm; The distance on the optical axis from the image-side surface of the first lens to the object-side surface of the second lens is L1, the distance on the optical axis from the image-side surface of the second lens to the object-side surface of the third lens is L2, the distance on the optical axis from the image-side surface of the third lens to the object-side surface of the fourth lens is L3, and the distance on the optical axis from the image-side surface of the fourth lens to the image plane is L4, where L1 = 5.331 ± 5% mm, L2 = 0.494 ± 5% mm, L3 = 0.5 ± 5% mm, and L4 = 145.626 ± 5% mm.

2. The telecentric plan lens according to claim 1, characterized in that, The center thickness of the first lens on the optical axis is d1, the center thickness of the second lens on the optical axis is d2, the center thickness of the third lens on the optical axis is d3, and the center thickness of the fourth lens on the optical axis is d4, wherein: 3.5mm≤d1≤4.5mm; 15.5mm≤d2≤16.5mm; 18.5mm≤d3≤20.5mm; 18.5mm≤d4≤20.5mm.

3. The telecentric plan lens according to claim 1, characterized in that, The aperture of the aperture stop is S1, and the distance between the aperture stop and the object side of the first lens on the optical axis is L5, where S1=14mm; L5=40mm.

4. The telecentric plan lens according to claim 1, characterized in that, The first lens, the second lens, the third lens, and the fourth lens are all made of fused silica glass.

5. The telecentric plan lens according to claim 1, characterized in that, The first lens, the second lens, the third lens, and the fourth lens all have the same refractive index and Abbe number.

6. The telecentric plan lens according to claim 5, characterized in that, The refractive index of the lens is Nd, and the Abbe number of the lens is Vd; where Nd = 1.64 ± 5% and Vd = 67.821 ± 5%.

7. The telecentric plan lens according to claim 1, characterized in that, The focal length of the telecentric plan lens is f, and the entrance pupil diameter of the telecentric plan lens is EPD, wherein 95mm < f < 105mm, and 13mm < EPD < 15mm.

8. A laser processing device, characterized in that, Includes the telecentric plan lens as described in any one of claims 1-7.

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