Flat-field focus lens with same focal length of red and blue wavebands

Abstract

The utility model provides a red-blue dual-band same-focal-length flat-field focus lens, which comprises an aperture grating and a lens group, the left side of the aperture grating is an object space, the right side of the aperture grating is an image space, and the lens group comprises a first lens, a second lens, a third lens, a fourth lens and a fifth lens which are sequentially arranged from the image space of the aperture grating. The image space of the lens group is provided with a protection window, and the working wave band of the flat-field focus lens is 455nmmp; the diameter of an incident light spot is 10mm, the focal length is 360mm, the working distance is 395mm, the working breadth is 300mm * 300mm, and the distance between the aperture diaphragm and the center of the first lens is 42mm, so that the problem that the achromatic field lens in the prior art cannot cope with blue light and infrared laser at different working distances and needs to adjust the divergence angle of the laser to realize the same working distance is solved; and meanwhile, after the laser is switched, engraving cannot be carried out on the same breadth.

Description

Technical Field

[0001] This utility model relates to the field of laser processing technology, and more specifically, to a flat-field focusing lens with the same focal length for both red and blue bands. Background Technology

[0002] The application of combined blue laser and infrared laser is becoming increasingly widespread, which places higher demands on the precision of the flat-field focusing lens during laser engraving. Currently, flat-field focusing lenses on the market are only suitable for single-band light sources. When switching between different lasers, flat-field focusing lenses are often not interchangeable. Moreover, because the wavelengths of infrared lasers (e.g., 1064±10nm) and blue lasers (e.g., 455±10nm) are far apart, color difference will inevitably occur, resulting in a large discrepancy between the trajectory marked by the red light and the engraving trajectory by the blue light, which seriously affects the engraving effect.

[0003] Current solutions mostly involve designing achromatic field lenses to reduce the chromatic difference between infrared laser wavelengths and blue light wavelengths. However, commercially available achromatic planar field lenses for blue and infrared lasers have different working distances, requiring adjustments to the divergence angle of the blue laser to achieve the same working distance. Furthermore, the different focal lengths and working areas of blue and infrared lasers prevent simultaneous engraving on the same area when switching lasers, and result in inconsistent line thicknesses during engraving, limiting their usability in certain environments. Utility Model Content

[0004] To overcome the above deficiencies, this invention provides a flat-field focusing lens with the same focal length for both red and blue bands, which solves the aforementioned problems.

[0005] This utility model is implemented as follows:

[0006] A flat-field focusing lens with red and blue dual-band same focal length includes an aperture grating and a lens group. The left side of the aperture grating is the object side, and the right side is the image side. The lens group includes a first lens, a second lens, a third lens, a fourth lens, and a fifth lens arranged sequentially from the image side of the aperture grating. A protective window is provided on the image side of the lens group. The working wavelength of the flat-field focusing lens is 455nm & 1064nm, the incident light spot diameter is 10mm, the focal length is 360mm, the working distance is 395mm, the working area is 300mm×300mm, and the center distance between the aperture stop and the first lens is 42mm.

[0007] In an embodiment of this utility model, the first lens is a meniscus H-K9L lens with positive optical power that bends towards the object side. Its radius of curvature on the object side is R11, its radius of curvature on the image side is R12, its center thickness on the optical axis is d1, its refractive index is Nd1=1.5168±5%, its Abbe number is Vd1=64.2±5%, and -50mm≤R11≤-60mm, -260mm≤R12≤-280mm, and 3mm≤d1≤5mm.

[0008] In an embodiment of this utility model, the second lens is a meniscus H-LAF50B lens with positive optical power that bends towards the object side. Its radius of curvature on the object side is R21, its radius of curvature on the image side is R22, its center thickness on the optical axis is d2, its refractive index is Nd2=1.7725±5%, its Abbe number is Vd2=49.6±5%, where -160mm≤R21≤-180mm, -60mm≤R22≤-70mm, and 9mm≤d2≤11mm.

[0009] In an embodiment of this utility model, the third lens is a meniscus H-LAK7A lens with positive optical power that bends towards the object side. Its radius of curvature on the object side is R31, its radius of curvature on the image side is R32, its center thickness on the optical axis is d3, its refractive index Nd3=1.713±5%, its Abbe number Vd3=53.83±5%, where -160mm≤R31≤-180mm, -110mm≤R32≤-130mm, and 5mm≤d3≤7mm.

[0010] In an embodiment of this utility model, the fourth lens is a meniscus ZF6 lens with positive optical power, curved towards the object side. Its radius of curvature on the object side is R41, its radius of curvature on the image side is R42, its center thickness on the optical axis is d4, its refractive index Nd4=1.95595±5%, its Abbe number Vd4=17.94±5%, where -100mm≤R41≤-110mm, -140mm≤R42≤-150mm, and 5mm≤d4≤7mm.

[0011] In an embodiment of this utility model, the fifth lens is a meniscus H-LAK7A lens with positive optical power that bends towards the object side. Its radius of curvature on the object side is R51, its radius of curvature on the image side is R52, its center thickness on the optical axis is d5, its refractive index Nd5=1.5928±5%, its Abbe number Vd5=68.34±5%, where -600mm≤R51≤-620mm, -600mm≤R52≤-620mm, and 9mm≤d5≤11mm.

[0012] In an embodiment of this utility model, the protective window is a flat glass H-K9L lens.

[0013] In an embodiment of this utility model, the distance on the optical axis from the image side of the first lens to the object side of the second lens is L1, the distance on the optical axis from the image side of the second lens to the object side of the third lens is L2, the distance on the optical axis from the image side of the third lens to the object side of the fourth lens is L3, the distance on the optical axis from the image side of the fourth lens to the object side of the fifth lens is L4, and the distance on the optical axis from the image side of the fifth lens to the protective window is L5, wherein 1mm≤L1≤2mm, 0mm≤L2≤1mm, 3mm≤L3≤4mm, 12mm≤L4≤14mm, and 2mm≤L5≤5mm.

[0014] In an embodiment of this utility model, the focal length of the plan focusing lens is f, and its entrance pupil diameter is EPD, where 350mm <f<380mm,10mm<EPD<14mm。

[0015] The beneficial effects of this utility model are as follows: This embodiment achieves a dual-band achromatic flat-field focusing lens for infrared and blue light by combining optical materials. When correcting the chromatic aberration and spherical aberration of infrared and blue light, this flat-field focusing lens focuses infrared and blue light to the same point, and the working surfaces of infrared and blue light are consistent. That is, when switching lasers, there is no need to adjust the working distance. At the same time, when the focal length and working area of ​​infrared and blue light are the same, when switching processing materials, there is no need to adjust the working area, and the thickness of the processed lines is always consistent. The optical materials in the lens group make both infrared and blue light have high transmittance, so that they can be transmitted efficiently during laser material processing, while ensuring that infrared and blue light are matched in time and space. Each lens has good thermal stability, which enables the flat-field focusing lens to have good high temperature resistance and can be used normally in high and low temperature environments. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of this utility model, the drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this utility model and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0017] Figure 1 An optical system diagram of a plan-field focusing lens provided for an embodiment of this utility model;

[0018] Figure 2 A dot matrix diagram corresponding to the infrared flat-field focusing lens provided for the embodiments of this utility model;

[0019] Figure 3Field curvature and distortion diagrams corresponding to the infrared flat-field focusing lens provided for embodiments of this utility model;

[0020] Figure 4 A dot plot corresponding to the blue light flat focusing lens provided for the embodiments of this utility model;

[0021] Figure 5 Field curvature and distortion diagrams corresponding to the blue light flat field focusing lens provided for embodiments of this utility model.

[0022] In the diagram: 1. Aperture grating; 2. Lens group; 21. First lens; 22. Second lens; 23. Third lens; 24. Fourth lens; 25. Fifth lens; 3. Protective window. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this utility model.

[0024] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0025] like Figure 1As shown, this utility model provides a plan-field focusing lens with the same focal length in both red and blue bands, including an aperture grating 1 and a lens assembly. The left side of the aperture grating 1 is the object side, and the right side is the image side. The lens assembly includes a first lens 21, a second lens 22, a third lens 23, a fourth lens 24, and a fifth lens 25 arranged sequentially from the image side of the aperture grating 1. A protective window 3 is provided on the image side of the lens assembly. The working wavelength of the plan-field focusing lens is 455nm & 1064nm, the incident light spot diameter is 10mm, the focal length is 360mm, the working distance is 395mm, and the working amplitude is... With a focal length of 300mm × 300mm and a center distance of 42mm between the aperture stop and the first lens 21, this solution provides a flat-field focusing lens with the same focal length in both red and blue bands. Through the combination of optical materials, the laser beam from the laser passes sequentially through the aperture stop, the first lens 21, the second lens 22, the third lens 23, the fourth lens 24, the fifth lens 25, and the protective window 3, converging at the imaging point on the working plane to achieve an infrared and blue dual-band achromatic flat-field focusing lens. Moreover, the infrared and blue light have the same focal length, the same working plane, and the same working distance.

[0026] The specific model parameters of the five lenses in the lens group are as follows:

[0027] The first lens 21 is a meniscus H-K9L lens with positive optical power, curved towards the object side. Its radius of curvature on the object side is R11, its radius of curvature on the image side is R12, its central thickness on the optical axis is d1, its refractive index is Nd1=1.5168±5%, its Abbe number is Vd1=64.2±5%, where -50mm≤R11≤-60mm, -260mm≤R12≤-280mm, and 3mm≤d1≤5mm.

[0028] The second lens 22 is a meniscus H-LAF50B lens with positive optical power, curved towards the object side. Its radius of curvature on the object side is R21, its radius of curvature on the image side is R22, its central thickness on the optical axis is d2, its refractive index is Nd2=1.7725±5%, its Abbe number is Vd2=49.6±5%, where -160mm≤R21≤-180mm, -60mm≤R22≤-70mm, and 9mm≤d2≤11mm.

[0029] The third lens 23 is a meniscus H-LAK7A lens with positive optical power, curved towards the object side. Its radius of curvature on the object side is R31, its radius of curvature on the image side is R32, its central thickness on the optical axis is d3, its refractive index is Nd3=1.713±5%, its Abbe number is Vd3=53.83±5%, where -160mm≤R31≤-180mm, -110mm≤R32≤-130mm, and 5mm≤d3≤7mm.

[0030] The fourth lens 24 is a meniscus ZF6 lens with positive optical power, curved towards the object side. Its radius of curvature on the object side is R41, its radius of curvature on the image side is R42, its central thickness on the optical axis is d4, its refractive index Nd4=1.95595±5%, its Abbe number Vd4=17.94±5%, where -100mm≤R41≤-110mm, -140mm≤R42≤-150mm, and 5mm≤d4≤7mm.

[0031] The fifth lens 25 is a meniscus H-LAK7A lens with positive optical power, curved towards the object side. Its radius of curvature on the object side is R51, its radius of curvature on the image side is R52, its central thickness on the optical axis is d5, its refractive index Nd5=1.5928±5%, its Abbe number Vd5=68.34±5%, where -600mm≤R51≤-620mm, -600mm≤R52≤-620mm, and 9mm≤d5≤11mm.

[0032] Furthermore, the distance on the optical axis from the image side of the first lens 21 to the object side of the second lens 22 is L1, the distance on the optical axis from the image side of the second lens 22 to the object side of the third lens 23 is L2, the distance on the optical axis from the image side of the third lens 23 to the object side of the fourth lens 24 is L3, the distance on the optical axis from the image side of the fourth lens 24 to the object side of the fifth lens 25 is L4, and the distance on the optical axis from the image side of the fifth lens 25 to the protective window 3 is L5, where 1mm≤L1≤2mm, 0mm≤L2≤1mm, 3mm≤L3≤4mm, 12mm≤L4≤14mm, and 2mm≤L5≤5mm.

[0033] It should be noted that the allowable error range is defined by the values ​​of the five lens parameters R11, R12, d1, R21, R22, d2, R31, R32, d3, R41, R42, d4, R51, R52, and d5. Within this range, the focal length of the plan-field focusing lens formed by any combination of parameters is f, and its entrance pupil diameter is EPD, where 350mm is an acceptable value. <f<380mm,10mm<EPD<14mm。

[0034] Among the parameters above, the curvature radius setting of each lens is used to correct aberrations in both infrared and blue lasers, thereby improving marking, welding, and cutting effects, meeting processing requirements, and reducing processing costs. The reasonable setting of the spacing between adjacent lenses balances the field curvature generated by the front and rear lenses in the plan-field focusing mirror, resulting in a reasonable field curvature. Setting the center thickness of the five lenses helps to ensure uniform lens size distribution, maintain assembly stability, reduce aberrations in the entire plan-field focusing mirror, and shorten its overall length. The Abbe number of a lens is an index representing the dispersion capability of a transparent medium; the more severe the dispersion, the smaller the Abbe number, and vice versa. The refractive index and Abbe number set in this embodiment are beneficial for achieving high pixel resolution in the plan-field focusing mirror, ensuring high transmittance for both infrared and blue light, thereby enabling efficient transmission during laser material processing and ensuring temporal and spatial matching between infrared and blue light.

[0035] In this embodiment, the protective window 3 is a flat glass H-K9L lens.

[0036] Specifically, by using the above-mentioned combination of lenses and a flat-field focusing lens, dual-band achromatic focusing on infrared and blue light is achieved. The laser beam passes through the object side of the aperture grating 1, and the chromatic aberration and spherical aberration of the infrared and blue light are corrected by the lens group 2, focusing the infrared and blue light to the same point. Since the working surfaces of the infrared and blue light are identical, there is no need to adjust the working distance when switching lasers. Therefore, when the focal lengths and working areas of the infrared and blue light are the same, switching processing materials does not require adjusting the working area, ensuring consistent line thickness. Figure 3 and Figure 5 As shown in the figure, it can be seen that the diffuse spots in all fields of view are within the diffraction-limited range, the light spots are uniform across the entire swath, all within the diffraction-limited range, and the distortion is less than 1%. Figure 4 The field curvature and distortion corresponding to mid-infrared and blue light in this flat field focusing lens show that the field curvature is within 1mm and the distortion is within 0.5%. This flat field focusing lens solves the problem that existing achromatic field lenses cannot handle blue light and infrared lasers at different working distances, and the laser divergence angle must be adjusted to achieve the same working distance. At the same time, it is impossible to engrave on the same surface after switching lasers.

[0037] The present invention has been further described above with reference to specific embodiments. However, it should be understood that the specific description herein should not be construed as limiting the substance and scope of the present invention. Various modifications made by those skilled in the art to the above embodiments after reading this specification are all within the scope of protection of the present invention.

Claims

1. A plan-field focusing lens with the same focal length in both red and blue bands, characterized in that, The system includes an aperture grating (1) and a lens assembly. The left side of the aperture grating (1) is the object side, and the right side is the image side. The lens assembly includes a first lens (21), a second lens (22), a third lens (23), a fourth lens (24), and a fifth lens (25) arranged sequentially from the image side of the aperture grating (1). The image side of the lens assembly is provided with a protective window (3). The working wavelength of the flat focusing lens is 455nm & 1064nm, the incident light spot diameter is 10mm, the focal length is 360mm, the working distance is 395mm, the working area is 300mm×300mm, and the center distance between the aperture stop and the first lens (21) is 42mm.

2. The plan-field focusing lens with the same focal length in both red and blue bands according to claim 1, characterized in that, The first lens (21) is a meniscus H-K9L lens with positive optical power that bends towards the object side. Its radius of curvature on the object side is R11, its radius of curvature on the image side is R12, its center thickness on the optical axis is d1, its refractive index is Nd1 = 1.5168 ± 5%, its Abbe number is Vd1 = 64.2 ± 5%, where -50mm ≤ R11 ≤ -60mm, -260mm ≤ R12 ≤ -280mm, and 3mm ≤ d1 ≤ 5mm.

3. A plan-field focusing lens with the same focal length for both red and blue bands according to claim 1, characterized in that, The second lens (22) is a meniscus H-LAF50B lens with positive optical power that bends towards the object side. Its radius of curvature on the object side is R21, its radius of curvature on the image side is R22, its center thickness on the optical axis is d2, its refractive index Nd2 = 1.7725 ± 5%, its Abbe number Vd2 = 49.6 ± 5%, where -160mm ≤ R21 ≤ -180mm, -60mm ≤ R22 ≤ -70mm, and 9mm ≤ d2 ≤ 11mm.

4. A plan-field focusing lens with the same focal length for both red and blue bands according to claim 1, characterized in that, The third lens (23) is a meniscus H-LAK7A lens with positive optical power that bends towards the object side. Its radius of curvature on the object side is R31, its radius of curvature on the image side is R32, its central thickness on the optical axis is d3, its refractive index is Nd3 = 1.713 ± 5%, its Abbe number is Vd3 = 53.83 ± 5%, where -160mm ≤ R31 ≤ -180mm, -110mm ≤ R32 ≤ -130mm, and 5mm ≤ d3 ≤ 7mm.

5. A plan-field focusing lens with the same focal length for both red and blue bands according to claim 1, characterized in that, The fourth lens (24) is a meniscus ZF6 lens with positive optical power that bends towards the object side. Its radius of curvature on the object side is R41, its radius of curvature on the image side is R42, its central thickness on the optical axis is d4, its refractive index Nd4 = 1.95595 ± 5%, its Abbe number Vd4 = 17.94 ± 5%, where -100mm ≤ R41 ≤ -110mm, -140mm ≤ R42 ≤ -150mm, and 5mm ≤ d4 ≤ 7mm.

6. A plan-field focusing lens with the same focal length for both red and blue bands according to claim 1, characterized in that, The fifth lens (25) is a meniscus H-LAK7A lens with positive optical power that bends towards the object side. Its radius of curvature on the object side is R51, its radius of curvature on the image side is R52, its center thickness on the optical axis is d5, its refractive index Nd5 = 1.5928 ± 5%, its Abbe number Vd5 = 68.34 ± 5%, where -600mm ≤ R51 ≤ -620mm, -600mm ≤ R52 ≤ -620mm, and 9mm ≤ d5 ≤ 11mm.

7. A plan-field focusing lens with the same focal length in both red and blue bands according to claim 1, characterized in that, The protective window (3) is a flat glass H-K9L lens.

8. A plan-field focusing lens with the same focal length in both red and blue bands according to any one of claims 1-7, characterized in that, The distance on the optical axis from the image side of the first lens (21) to the object side of the second lens (22) is L1, the distance on the optical axis from the image side of the second lens (22) to the object side of the third lens (23) is L2, the distance on the optical axis from the image side of the third lens (23) to the object side of the fourth lens (24) is L3, the distance on the optical axis from the image side of the fourth lens (24) to the object side of the fifth lens (25) is L4, and the distance on the optical axis from the image side of the fifth lens (25) to the protective window (3) is L5, where 1mm≤L1≤2mm, 0mm≤L2≤1mm, 3mm≤L3≤4mm, 12mm≤L4≤14mm, and 2mm≤L5≤5mm.

9. A plan-field focusing lens with the same focal length in both red and blue bands according to claim 8, characterized in that, The focal length of the plan focusing lens is f, and its entrance pupil diameter is EPD, where 350mm is the focal length of the lens. <f<380mm,10mm<EPD<14mm。

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