An achromatic objective

Abstract

The utility model discloses a kind of achromatic objective, comprising: chromatic aberration pre-correction group, main focusing group and high chromatic aberration compensation group;The utility model adopts the three-section structure design of chromatic aberration pre-correction group, main focusing group, high chromatic aberration compensation group, each group of lens is cooperatively configured in optical power, material abbe number and arrangement order, chromatic aberration pre-correction group is combined by negative optical power and positive optical power lens, wavelength difference caused by optical path deviation is pre-corrected before light enters main focusing area, so that the light of different wavelengths has the propagation direction of preliminary convergence, compared with the field lens system of traditional chromatic aberration control only relying on main focusing unit, the structure reduces the cumulative error of dispersion superposition at source, improves the fault tolerance of system to residual chromatic aberration, thereby significantly improve the achromatic ability and focal point coincidence precision of entire system.

Description

Technical Field

[0001] This utility model relates to the field of objective lens technology, and in particular to an achromatic objective lens. Background Technology

[0002] In many fields such as laser processing, optical imaging, and machine vision, it is often necessary to process light of different wavelengths simultaneously. For example, in laser processing systems, 1064nm wavelength lasers are commonly used for material processing, while 633nm wavelength visible light (such as helium-neon lasers) can be used for optical path indication or visual imaging assistance. However, traditional optical lenses suffer from chromatic aberration, meaning that light of different wavelengths has different focal lengths after passing through the lens, leading to blurred images or reduced processing accuracy.

[0003] For objective lenses, while focusing light, it is necessary to ensure that light of different wavelengths has the same focusing effect on the focal plane. In practical applications, due to the difference in refractive index of different wavelengths of light, when 1064nm laser light and 633nm visible light pass through ordinary objective lenses, significant chromatic aberration occurs, making it impossible to simultaneously achieve clear imaging or precise processing on the same focal plane. This chromatic aberration problem severely limits the application of objective lenses in systems with high requirements for different wavelengths of light. Currently, although some achromatic technologies and products exist, there is a lack of achromatic objective lenses with large incident light apertures in some quartz lenses specifically designed for short focal lengths and wavelengths of 1064nm and 633nm. Existing technologies are insufficient to meet the high-precision achromatic aberration requirements for this specific focal length and wavelength combination.

[0004] Therefore, it is necessary to design an achromatic objective lens to solve the above problems. Utility Model Content

[0005] This invention overcomes the shortcomings of the prior art and provides an achromatic objective lens.

[0006] To achieve the above objectives, the technical solution adopted by this utility model is as follows: an achromatic objective lens, comprising: a chromatic aberration pre-correction group, a main focusing group, and a high chromatic aberration compensation group;

[0007] The chromatic aberration pre-correction group includes at least one negative optical power lens and at least one positive optical power lens, whose combined optical power is negative, and is used to generate pre-compensation chromatic aberration before light enters the main focusing module.

[0008] The main focusing group includes at least one positive power lens for converging pre-corrected light rays onto the target focal plane;

[0009] The high chromatic aberration compensation group includes at least one negative power high dispersion lens and at least one positive power lens, used for inverse compensation of dual-wavelength residual chromatic aberration.

[0010] In a preferred embodiment of this utility model, the chromatic aberration pre-correction group includes a first lens and a second lens; the first lens and the second lens are arranged in sequence, wherein the first lens is a biconcave lens with negative optical power, and the second lens is a meniscus lens with positive optical power.

[0011] In a preferred embodiment of this invention, the refractive index of the first lens is between 1.3 mm and 1.6 mm, and the Abbe number is between 40 mm and 80 mm; the refractive index of the second lens is between 1.6 mm and 1.8 mm, and the Abbe number is between 35 mm and 55 mm.

[0012] In a preferred embodiment of this utility model, the main focusing group includes: a third lens; the third lens is a biconvex lens with positive optical power, the refractive index of the third lens is between 1.6mm and 1.8mm, and the Abbe number is between 35mm and 55mm.

[0013] In a preferred embodiment of this utility model, the high chromatic aberration compensation group includes a fourth lens and a fifth lens; the fourth lens and the fifth lens are arranged sequentially, wherein the fourth lens is a biconcave lens with negative optical power, and the fifth lens is a meniscus lens with positive optical power.

[0014] In a preferred embodiment of this utility model, the refractive index of the fourth lens is between 1.8 mm and 2.0 mm, and the Abbe number is between 15 mm and 25 mm; the refractive index of the fifth lens is between 1.6 mm and 1.8 mm, and the Abbe number is between 35 mm and 55 mm.

[0015] In a preferred embodiment of the present invention, the object side curvature radius of the first lens is between -40mm and -60mm, and the image side curvature is between 340mm and 380mm.

[0016] The second lens has an object-side radius of curvature between -180mm and -200mm, and an image-side radius of curvature between -70mm and -90mm.

[0017] The third lens has an object-side radius of curvature between 440mm and 460mm, and an image-side radius of curvature between -95mm and -115mm.

[0018] The fourth lens has an object-side radius of curvature between -110mm and -130mm, and an image-side radius of curvature between -2500mm and -3500mm.

[0019] The fifth lens has an object-side radius of curvature between 700mm and 720mm, and an image-side radius of curvature between -150mm and -170mm.

[0020] In a preferred embodiment of this utility model,

[0021] The distance between the first lens and the second lens is 6mm to 8mm;

[0022] The distance between the second lens and the third lens is 0mm to 1mm;

[0023] The distance between the third lens and the fourth lens is 16mm to 18mm;

[0024] The distance between the fourth lens and the fifth lens is 1mm to 3mm.

[0025] In a preferred embodiment of this invention, the effective focal length of the achromatic objective lens is 170mm, and the total length L is between 80mm and 100mm.

[0026] In a preferred embodiment of this utility model, the first lens is made of JGS1 glass; the second lens, the third lens, and the fifth lens are made of HLAF50B glass; and the fourth lens is made of HZF88 glass.

[0027] This utility model solves the defects existing in the background technology, and has the following beneficial effects:

[0028] (1) This utility model provides an achromatic objective lens with a three-section structure design of a chromatic aberration pre-correction group, a main focusing group, and a high chromatic aberration compensation group. Each group of lenses is configured in coordination in terms of optical power, material Abbe number, and arrangement order. The chromatic aberration pre-correction group, through the combination of negative and positive optical power lenses, pre-corrects the optical path offset caused by the wavelength difference before the light enters the main focusing area, so that light of different wavelengths has a preliminary convergence of propagation direction. Compared with the traditional field lens system that only relies on the main focusing unit to control chromatic aberration, this structure reduces the cumulative error of dispersion superposition at the source, improves the system's tolerance to residual chromatic aberration, and thus significantly improves the achromatic aberration capability and focus coincidence accuracy of the entire system.

[0029] (2) This invention introduces a low Abbe number negative power high dispersion material lens in the high chromatic aberration compensation group, and forms a reverse chromatic aberration correction structure with a positive power lens. This group design utilizes the strong refractive response of the high dispersion material to different wavelengths to achieve reverse compensation for the residual chromatic aberration between 1064nm and 633nm, so that wavelength re-synthesizing can be achieved at the focal plane. Compared with the existing technology that only uses ordinary optical glass for compensation or does not explicitly divide the chromatic aberration control group, this solution can achieve higher chromatic aberration compensation efficiency in a shorter total optical length, and finally obtain a precise focusing effect with a chromatic aberration offset of less than 0.02mm, providing a solid optical foundation for high-precision laser processing and dual-wavelength coaxial imaging. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a three-dimensional structural diagram of the objective lens of this utility model;

[0032] Figure 2 This is the optical path diagram of the objective lens of this utility model;

[0033] In the diagram: 1. First lens; 2. Second lens; 3. Third lens; 4. Fourth lens; 5. Fifth lens. Detailed Implementation

[0034] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0035] Many specific details are set forth in the following description in order to provide a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the scope of protection of the present invention is not limited to the specific embodiments disclosed below.

[0036] In the description of this application, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting the scope of protection of this application. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this utility model, unless otherwise stated, "a plurality of" means two or more.

[0037] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art will understand the specific meaning of the above terms in this application based on the specific circumstances.

[0038] like Figure 1 As shown, an achromatic objective lens includes: a chromatic aberration pre-correction group, a main focusing group, and a high chromatic aberration compensation group;

[0039] The chromatic aberration pre-correction group includes at least one negative optical power lens and at least one positive optical power lens, whose combined optical power is negative, and is used to generate pre-compensation chromatic aberration before light enters the main focusing module.

[0040] The main focusing group includes at least one positive power lens for converging pre-corrected light rays onto the target focal plane;

[0041] The high chromatic aberration compensation group includes at least one negative power high dispersion lens and at least one positive power lens, used for inverse compensation of dual-wavelength residual chromatic aberration.

[0042] The chromatic aberration pre-correction group consists of at least one negative power lens and one positive power lens, with a combined negative power. This allows the incident light to begin receiving preliminary dispersion control before entering the main focusing group. It is used to "move forward" the chromatic aberration correction process. That is, by using optical materials with a small refractive index difference and a large Abbe number, the chromatic path difference between 633nm and 1064nm is expanded and guided in the initial stage of the system's optical path, reducing the subsequent compensation pressure and improving the overall chromatic aberration correction efficiency of the system.

[0043] The main focusing group contains at least one positive power lens, which serves as the main focusing force of the system. Its main function is to efficiently converge the two wavelengths of light after pre-correction to the target focal plane. It uses medium Abbe number material and adopts a biconvex shape to ensure strong focusing ability while effectively suppressing the amplification trend of spherical aberration and axial chromatic aberration caused by focal length compression, providing good optical path incident conditions and focal approach basis for the final chromatic aberration compensation group.

[0044] The high chromatic aberration compensation group at the end of the optical path contains at least one negative power lens with high dispersion and low Abbe number and one positive power lens. Through a precisely designed reverse chromatic aberration path structure, the residual dispersion of the dual-wavelength light is reversed and compensated. For example, the application of high dispersion material HZF88 makes the compensation group have a significant response capability to changes in refractive index at different wavelengths. It can suppress residual chromatic aberration and restore wavefront consistency within a limited structural length, thereby ensuring that the 1064nm and 633nm light rays eventually coincide in space at the focal plane.

[0045] In this invention, the chromatic aberration pre-correction group includes a first lens 1 and a second lens 2; the first lens 1 and the second lens 2 are arranged in sequence, wherein the first lens 1 is a biconcave lens with negative optical power, and the second lens 2 is a meniscus lens with positive optical power.

[0046] The refractive index of the first lens 1 is between 1.3 mm and 1.6 mm, and the Abbe number is between 40 mm and 80 mm; the refractive index of the second lens 2 is between 1.6 mm and 1.8 mm, and the Abbe number is between 35 mm and 55 mm.

[0047] The light is diverged by the biconcave lens, while the meniscus lens initially converges some of the diverging light. However, since the overall focal power of this group is still negative, it still dominates the diverging trend of the light, thereby achieving dispersion control in the initial stage of objective lens incidence.

[0048] The first lens 1 and the second lens 2 can intentionally separate the propagation paths of 633nm and 1064nm light in space, making it easier to achieve reverse convergence in the subsequent main focusing group and high chromatic aberration compensation group. Compared with the existing technology that uses a single positive lens for direct focusing, the dispersion preprocessing of the dual-lens structure is more in line with the chromatic aberration control requirements of the composite wavelength system. It can achieve greater chromatic aberration mitigation capability without increasing the system thickness, and improve the chromatic aberration tolerance of the optical system.

[0049] In this invention, the main focusing group includes: a third lens 3; the third lens 3 is a biconvex lens with positive optical power, the refractive index of the third lens 3 is between 1.6mm and 1.8mm, and the Abbe number is between 35mm and 55mm.

[0050] After the beam has undergone chromatic aberration pre-expansion and optical path guidance, a lens assembly with strong focusing capability and good wavefront control performance is needed to focus light of different wavelengths onto a unified focal plane. Therefore, the third lens 3 with a biconvex structure has positive curvature on both sides, which can provide a stable and efficient positive focal effect within a short structural length, so that the incident beam converges quickly and the system focal length is reduced.

[0051] Meanwhile, the Abbe number of the lens material is between 35mm and 55mm, which gives it a certain dispersion capability while avoiding excessive expansion of chromatic aberration, leaving reasonable compensation space for the high chromatic aberration compensation group in the subsequent stage. Under the premise that the chromatic aberration path difference has been initially adjusted by the pre-stage lens group, the main focusing lens achieves the establishment of the "convergence center" through stable focusing, that is, guiding the light of the two wavelengths to the closest point in physical space as much as possible.

[0052] In this invention, the high chromatic aberration compensation group includes a fourth lens 4 and a fifth lens 5; the fourth lens 4 and the fifth lens 5 are arranged sequentially, wherein the fourth lens 4 is a biconcave lens with negative optical power, and the fifth lens 5 is a meniscus lens with positive optical power.

[0053] The refractive index of the fourth lens 4 is between 1.8 mm and 2.0 mm, and the Abbe number is between 15 mm and 25 mm; the refractive index of the fifth lens 5 is between 1.6 mm and 1.8 mm, and the Abbe number is between 35 mm and 55 mm.

[0054] It should be noted that by setting the fourth lens 4 and the fifth lens 5, the axial chromatic aberration and lateral chromatic aberration that remain after the initial focusing are precisely compensated at the end of the optical path, so as to achieve spatial overlap of the wavelength convergence point and ensure that different wavelengths of light are finally focused on the same focal plane.

[0055] Among them, the fourth lens 4, by adopting a biconcave shape and high dispersion glass material, can re-spread different wavelengths of light with its negative optical power, so that the path difference between short wavelength 633nm and long wavelength 1064nm light is actively amplified. Then, the fifth lens 5, with its positive optical power and symmetrical curvature, re-converges these two types of light onto a unified focal plane, thereby achieving reverse dispersion compensation.

[0056] In this invention, the object side curvature radius of the first lens 1 is between -40mm and -60mm, and the image side curvature is between 340mm and 380mm; it has asymmetric surface features, that is, the front surface has strong negative curvature and the rear surface has large positive curvature. By introducing a certain amount of spherical aberration and chromatic aberration for initial unfolding, it is beneficial for subsequent optical path pre-compensation.

[0057] The object-side radius of curvature of the second lens 2 is between -180mm and -200mm, and the image-side radius of curvature is between -70mm and -90mm; the overall structure is an "concave-convex" asymmetrical structure. This structure can effectively work in conjunction with the first lens 1 to achieve preliminary chromatic aberration stretching and beam parallelism control, ensuring that the light rays incident on the main focusing group are at the appropriate angle;

[0058] The object side curvature radius of the third lens 3 is between 440mm and 460mm, and the image side curvature radius is between -95mm and -115mm. By combining the large positive curvature front and the moderate negative curvature rear, a strong convergence function is formed, realizing the core function of the mid-section focusing, controlling the main beam diameter, compressing the focal length, and laying the foundation for the final chromatic aberration closure.

[0059] The object-side radius of curvature of the fourth lens 4 is between -110mm and -130mm, and the image-side radius of curvature is between -2500mm and -3500mm.

[0060] The object side curvature radius of the fifth lens 5 is between 700mm and 720mm, and the image side curvature radius is between -150mm and -170mm.

[0061] In this utility model,

[0062] The distance between the first lens 1 and the second lens 2 is 6mm to 8mm; this allows the light rays diverging from the first lens 1 to form a certain free propagation range before entering the second lens 2, so that different wavelengths of light can naturally separate their propagation angles in this range.

[0063] The distance between the second lens 2 and the third lens 3 is 0mm to 1mm;

[0064] The distance between the third lens 3 and the fourth lens 4 is 16mm to 18mm, which makes the dual-wavelength light rays form a clear convergence trend after passing through the main focusing lens, and further accumulate chromatic aberration value in this segment; this time delay amplification mechanism enables subsequent lenses with higher dispersion intensity, such as the fourth lens 4, to perform efficient compensation in the stage where "chromatic aberration is more obvious".

[0065] The distance between the fourth lens 4 and the fifth lens 5 is 1mm to 3mm; this allows the fifth lens 5 to "compress and integrate" the residual chromatic aberration compensation from the previous stage within a shorter distance, forming a final unified focal position.

[0066] By controlling the axial spacing between lenses, the propagation path of light maintains optimal propagation phase and incident angle conditions in each group, avoiding excessive dispersion stretching or accumulation of secondary spherical aberration.

[0067] like Figure 2 As shown, in this invention, the effective focal length of the achromatic objective lens is 170mm, and the total length L is between 80mm and 100mm.

[0068] During assembly, the spacing between the first lens 1 and the second lens 2 is controlled to be 7mm, the spacing between the second lens 2 and the third lens 3 is 0.5mm, the spacing between the third lens 3 and the fourth lens 4 is 17mm, and the spacing d8 between the fourth lens 4 and the fifth lens 5 is 2mm.

[0069] After assembly, the achromatic field lens was adjusted using light sources with wavelengths of 1064nm and 633nm. By adjusting the axial position and angle of the lens, the two wavelengths of light were focused to achieve the best focusing effect on the focal plane, ultimately resulting in a 1064+633 achromatic field lens with a focal length of 170mm.

[0070] In this utility model,

[0071] The first lens 1 is made of JGS1 glass material, with a refractive index nd1 of approximately 1.46 and an Abbe number vd1 of approximately 67.8.

[0072] The second lens 2 is made of HLAF50B glass material, with a refractive index nd2 of approximately 1.77 and an Abbe number vd2 of approximately 49.6.

[0073] The third lens 3 is made of HLAF50B glass.

[0074] The fourth lens 4 is made of HZF88 glass material, with a refractive index nd4 of approximately 1.95 and an Abbe number vd4 of approximately 17.9.

[0075] The fifth lens 5 is made of HLAF50B glass.

[0076] Based on the preferred embodiments of this utility model described above, those skilled in the art can make various changes and modifications without departing from the technical concept of this utility model. The technical scope of this utility model is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. An achromatic objective lens, characterized in that, include: Color difference pre-correction group, main focus group, and high color difference compensation group; The chromatic aberration pre-correction group includes at least one negative optical power lens and at least one positive optical power lens, whose combined optical power is negative, and is used to generate pre-compensation chromatic aberration before light enters the main focusing module. The main focusing group includes at least one positive power lens for converging pre-corrected light rays onto the target focal plane; The high chromatic aberration compensation group includes at least one negative power high dispersion lens and at least one positive power lens, used for inverse compensation of dual-wavelength residual chromatic aberration.

2. An achromatic objective lens according to claim 1, characterized in that: The chromatic aberration pre-correction group includes a first lens (1) and a second lens (2); the first lens (1) and the second lens (2) are arranged in sequence, wherein the first lens (1) is a biconcave lens with negative optical power, and the second lens (2) is a meniscus lens with positive optical power.

3. An achromatic objective lens according to claim 2, characterized in that: The first lens (1) has a refractive index between 1.3 mm and 1.6 mm and an Abbe number between 40 mm and 80 mm; the second lens (2) has a refractive index between 1.6 mm and 1.8 mm and an Abbe number between 35 mm and 55 mm.

4. An achromatic objective lens according to claim 3, characterized in that: The main focusing group includes: a third lens (3); the third lens (3) is a biconvex lens with positive optical power, the refractive index of the third lens (3) is between 1.6 mm and 1.8 mm, and the Abbe number is between 35 mm and 55 mm.

5. An achromatic objective lens according to claim 4, characterized in that: The high chromatic aberration compensation group includes a fourth lens (4) and a fifth lens (5); the fourth lens (4) and the fifth lens (5) are arranged in sequence, wherein the fourth lens (4) is a biconcave lens with negative optical power, and the fifth lens (5) is a meniscus lens with positive optical power.

6. An achromatic objective lens according to claim 5, characterized in that: The refractive index of the fourth lens (4) is between 1.8 mm and 2.0 mm, and the Abbe number is between 15 mm and 25 mm; the refractive index of the fifth lens (5) is between 1.6 mm and 1.8 mm, and the Abbe number is between 35 mm and 55 mm.

7. An achromatic objective lens according to claim 6, characterized in that: The object side curvature radius of the first lens (1) is between -40mm and -60mm, and the image side curvature is between 340mm and 380mm. The object side radius of curvature of the second lens (2) is between -180mm and -200mm, and the image side radius of curvature is between -70mm and -90mm; The object side curvature radius of the third lens (3) is between 440mm and 460mm, and the image side curvature radius is between -95mm and -115mm. The object side curvature radius of the fourth lens (4) is between -110mm and -130mm, and the image side curvature radius is between -2500mm and -3500mm. The fifth lens (5) has an object side curvature radius between 700mm and 720mm and an image side curvature radius between -150mm and -170mm.

8. An achromatic objective lens according to claim 7, characterized in that: The distance between the first lens (1) and the second lens (2) is 6mm to 8mm; The distance between the second lens (2) and the third lens (3) is 0mm to 1mm; The distance between the third lens (3) and the fourth lens (4) is 16mm to 18mm; The distance between the fourth lens (4) and the fifth lens (5) is 1mm to 3mm.

9. An achromatic objective lens according to claim 1, characterized in that: The effective focal length of the achromatic objective lens is 170mm, and the total length L is between 80mm and 100mm.

10. An achromatic objective lens according to claim 8, characterized in that: The first lens (1) is made of JGS1 glass; the second lens (2), the third lens (3), and the fifth lens (5) are made of HLAF50B glass; and the fourth lens (4) is made of HZF88 glass.

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