Near ultraviolet light convergence lens of multimode optical fiber

Abstract

The utility model provides a near ultraviolet light convergence lens of a multimode optical fiber, which comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens and a sixth lens which are sequentially arranged from an object side to an image side, the first lens is a meniscus lens with a concave surface facing an imaging surface, the second lens, the third lens and the fifth lens are biconvex lenses, and the sixth lens is a biconvex lens with a concave surface facing an imaging surface. The fourth lens is a meniscus lens and the concave surface faces the object side. The sixth lens is a biconcave lens. According to the convergent lens for the multimode optical fiber, light output by the multimode optical fiber is converged, the core diameter of the multimode optical fiber can reach 910 micrometers, the numerical aperture can reach 0.2, the distance between an image side convergence point and the image side face of the sixth lens can reach 200 mm or above, and the convergent lens for the multimode optical fiber is good in imaging uniformity and small in chromatic aberration under near ultraviolet light and visible light within the wave band range of 320-550 nanometers.

Description

Technical Field

[0001] The utility model relates to the field of applied optical technology, in particular to a near-ultraviolet light converging lens for a multimode optical fiber, which is suitable for converging light emitted by a multimode optical fiber in the field of high-energy laser applications. Background Art

[0002] In the field of high-energy laser applications, in order to solve the problem of flexible transmission of light energy, the spatial light emitted by the laser can be coupled to an optical fiber for transmission. A lens is used at the output end of the optical fiber to converge the light and achieve operation at the desired image-side convergence point. After the laser is coupled through the optical fiber, the straight-line transmission path of the light beam can be changed, thereby reducing the limitation of the transmission space, but there is also the problem of low laser-to-fiber coupling efficiency. In order to improve the fiber coupling efficiency, this can be achieved by increasing the numerical aperture and core diameter of the optical fiber. Since the application field generally requires the laser to be converged before working, the divergent light beam at the output end of the optical fiber needs to be converged through a converging lens. However, increasing the numerical aperture and core diameter of the optical fiber increases the aberration of the converging lens, making laser convergence difficult. In particular, when converging laser beams of multiple wavelengths and near-ultraviolet wavelengths at the same time, chromatic aberration makes convergence even more difficult.

[0003] In order to solve the problem that it is difficult to converge laser beams of multiple wavelengths after being coupled through a multimode optical fiber, the utility model provides a near-ultraviolet light converging lens for a multimode optical fiber. Utility Model Content

[0004] The utility model aims to provide a converging lens for multimode optical fibers with small converging spot diameter and uniform light energy distribution.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a near-ultraviolet light converging lens for a multimode optical fiber, comprising a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens arranged in sequence along an optical axis from the object side to the image side, wherein the first to sixth lenses each include an object-side surface facing the object side and allowing imaging light to pass therethrough, and an image-side surface facing the image side and allowing imaging light to pass therethrough;

[0006] The first lens is a meniscus-shaped glass spherical lens with a concave surface facing the image side and has negative optical power;

[0007] The second lens is a biconvex glass spherical lens with positive optical power;

[0008] The third lens is a biconvex glass spherical lens with positive focal power;

[0009] The fourth lens is a meniscus-shaped glass spherical lens with a concave surface facing the object side and has negative optical power;

[0010] The fifth lens is a biconvex glass spherical lens with a positive optical power;

[0011] The sixth lens is a biconcave glass spherical lens with a negative optical power.

[0012] Further, in the near-ultraviolet light converging lens of a multimode optical fiber, during operation, the object plane is located 109 - 108 mm in front of the object side of the first lens, and the object-side numerical aperture is 0.2.

[0013] Further, after the light passes through this lens, the converging point is located at an image plane position 198 - 203 mm behind the image side of the sixth lens.

[0014] Further, this lens satisfies: 60 < vd1 < 70, 85 < vd2 < 100, 85 < vd3 < 100, 60 < vd4 < 70, 85 < vd5 < 100, 60 < vd6 < 70, where vd1, vd2, vd3, vd4, vd5, vd6 are the dispersion coefficients of the first lens, second lens, third lens, fourth lens, fifth lens, and sixth lens, respectively.

[0015] Further, this lens satisfies the following conditional expressions: -95 < f1′ < -110, 60 < f2 ′ <68, 62 < f3′ < 70, -85 < f4′ < -96, 63 < f5′ < 72, -56 < f6′ < -67, where f1′, f3′, f4′, f5′, f6′ are the focal lengths of the first lens, second lens, third lens, fourth lens, fifth lens, and sixth lens, respectively.

[0016] Further, this lens satisfies the following conditional expressions: 1.40 < nd1 < 1.54, 1.43 < nd2 < 1.50, 1.43 < nd3 < 1.50, 1.40 < nd4 < 1.54, 1.43 < nd5 < 1.50, 1.40 < nd6 < 1.54, where nd1, nd2, nd3, nd4, nd5, nd6 are the refractive indices of the first lens, second lens, third lens, fourth lens, fifth lens, and sixth lens, respectively.

[0017] Further, the focal length f′ of this lens is 76.823 mm.

[0018] After adopting the above technical solutions, the present utility model has the following advantages: The near-ultraviolet light converging lens of a multimode optical fiber provided by the present utility model has a large object-side numerical aperture, a large distance between the image-side converging point and the image side of the sixth lens during operation, a small converging point spot diameter, a uniform spot energy distribution, a large optical fiber core diameter, and can transmit high energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of the lens structure according to an embodiment of the present invention;

[0020] Figure 2 Schematic diagram of the optical path operation according to an embodiment of the present invention;

[0021] Figure 3 Spot diagram of the lens aberration according to an embodiment of the present invention;

[0022] Figure 4 Radial energy analysis diagram according to an embodiment of the present invention; Specific implementation manners

[0023] The present invention provides a near-ultraviolet light converging lens for multimode optical fibers, which can be used in cooperation with multimode optical fibers to converge the divergent light beam emitted from the multimode optical fiber to the image plane position. Its position layout from the output end of the multimode optical fiber to the converging plane is successively: the output end face of the multimode optical fiber, the lens group, and the image-side converging plane. Among them, the output end face of the multimode optical fiber is also called the object plane, the numerical aperture of the multimode optical fiber, that is, the object-side numerical aperture, is 0.2, and the core diameter of the multimode optical fiber is the object plane height.

[0024] The following further describes the present invention in detail in conjunction with embodiments and drawings. The terms "first", "second", "third", "fourth", "fifth", "sixth", etc. used herein do not limit the data and execution order, but only distinguish the same items or similar items with basically the same functions and effects. The specific embodiments are only used to explain the present application and do not limit the present application.

[0025] An embodiment of the present invention provides a near-ultraviolet light converging lens for multimode optical fibers. Please refer to Figure 1 , which shows the structure of an optical lens provided by an embodiment of the present invention. The optical lens includes a first lens 1, a second lens 2, a third lens 3, a fourth lens 4, a fifth lens 5, and a sixth lens 6 arranged successively from the object plane to the image plane.

[0026] [[ID=二十九]]In this embodiment, the first lens 1 is a meniscus-shaped glass spherical lens with a concave surface facing the image side and has a negative optical power; the second lens 2 is a biconvex glass spherical lens and has a positive optical power; the first lens 1 and the second lens 2 form a lens group with a positive optical power and satisfy: 60 < vd1 < 70, 85 < vd2 < 100, 1.40 < nd1 < 1.54, 1.43 < nd2 < 1.50, where vd1 and vd2 are the dispersion coefficients of the first lens 1 and the second lens 2 respectively, and nd1 and nd2 are the refractive indices of the first lens 1 and the second lens 2 respectively. The first lens 1 and the second lens 2 correct spherical aberration by having negative and positive optical powers respectively, and correct chromatic aberration by having different dispersion rates and refractive indices respectively.

[0027] It should be noted that there is an error in the numbering in the original text. The last item should be numbered as instead of [[ID=二十九]]. The above translation has been adjusted accordingly.The third lens 3 is a biconvex glass spherical lens with a positive optical power; the fourth lens 4 is a meniscus-shaped glass spherical lens with a concave surface facing the image side and has a negative optical power; the third lens 3 and the fourth lens 2 form a lens group with a positive optical power, and satisfy: 1.43 < nd3 < 1.50, 1.40 < nd4 < 1.54, 1.43 < nd3 < 1.50, 1.40 < nd4 < 1.54, where vd3 and vd4 are the dispersion coefficients of the third lens 3 and the fourth lens 4 respectively, and nd3 and nd4 are the refractive indices of the third lens 3 and the fourth lens 4 respectively. The third lens 3 and the fourth lens 4 correct spherical aberration by having positive and negative optical powers respectively, and correct chromatic aberration by having different dispersion rates and refractive indices respectively.

[0028] The lens group composed of the first lens 1 and the second lens 2 has a symmetric structure in shape with the lens group composed of the third lens 3 and the fourth lens 4, thereby further reducing chromatic aberration. Note that the symmetric structure described here does not mean that the values are exactly the same.

[0029] The fifth lens 5 is a biconvex glass spherical lens with a positive optical power; the sixth lens 6 is a biconcave glass spherical lens with a negative optical power; the fifth lens 5 and the sixth lens 6 form a lens group with a positive optical power, and its combined focal length is 6890.6348 mm, and satisfy: 85 < vd5 < 100, 60 < vd6 < 70, 1.43 < nd5 < 1.50, 1.40 < nd6 < 1.54, where vd5 and vd6 are the dispersion coefficients of the fifth lens 5 and the sixth lens 6 respectively, and nd5 and nd6 are the refractive indices of the fifth lens 5 and the sixth lens 6 respectively. The fifth lens 5 and the sixth lens 6 further correct chromatic spherical aberration by having positive and negative optical powers respectively and having different dispersion rates respectively.

[0030] For the near-ultraviolet light converging lens of a multimode optical fiber described above, please refer to Figure 2 When in use, place the exit surface of the multimode optical fiber at a position 109 - 108 mm in front of the object side surface of the first lens 1. This position is the position of the object surface 7 for the converging lens, and its object-side aperture angle can reach 0.2.

[0031] For the near-ultraviolet light converging lens of a multimode optical fiber described above, when in use, after the light beam emitted from the multimode optical fiber is converged by the converging lens, the image plane is located at a position 198 - 203 mm from the image side surface of the sixth lens. This position is the position of the image plane 8 for the converging lens. The large distance between the image plane and the image side surface of the sixth lens is convenient for use and meets the requirements of beam focusing.

[0032] For the near-ultraviolet light converging lens of a multimode optical fiber described above, please refer to Figure 3The point diagram shows that the numerical aperture of the beam passing through the exit surface of the multimode optical fiber is 0.2. After being converged by the converging lens, the root mean square diameter of the diffuse spot is less than 0.2 mm, and the diameter of the diffuse spot with 100% energy is less than 0.331 mm.

[0033] The multimode optical fiber near ultraviolet light focusing lens, see Figure 4 The radial energy analysis diagram shows that within 100% of the diffuse spot diameter, the energy distribution increases linearly with the diffuse spot diameter, indicating that the spot energy distribution is uniform.

[0034] Table 1 shows the basic parameters of a multimode optical fiber near-ultraviolet light converging lens of this embodiment:

[0035] Table 1

[0036] surface Radius of curvature thickness Refractive index dispersion coefficient focal length Physical Surface Infinity 108.15 -102.4859 First lens Infinity 3.5 1.4584 67.79 47.83 0.1 Second lens 47.8 16.5 1.4338 94.95 63.2847 -59.5 2 The third lens 78.67 16 1.4338 94.95 67.0522 -44.19 0.23 Fourth lens -43.3 4.2 1.4584 67.79 -91.1919 2564 1 Fifth lens 61.12 16.2 1.4338 94.95 67.4509 -52.9 0.23 Sixth lens -53.2 3.5 1.4584 67.79 -61.2818 63.14576 202 Image plane Infinity

Claims

1. A multimode optical fiber near-ultraviolet light converging lens, characterized in that: From the object side to the image side, it successively includes: A first lens with negative optical power, the first lens being a meniscus-shaped glass spherical lens with the concave surface facing the image side; A second lens with positive optical power, the second lens being a biconvex glass spherical lens; A third lens with positive optical power, the third lens being a biconvex glass spherical lens; A fourth lens with negative optical power, the fourth lens being a meniscus-shaped glass spherical lens with the concave surface facing the object side; A fifth lens with positive optical power, the fifth lens being a biconvex glass spherical lens; A sixth lens with negative optical power, the sixth lens being a biconcave glass spherical lens; The near-ultraviolet light converging lens of a multimode optical fiber has a working wavelength of 320 - 550 nm.

2. The multimode optical fiber near-ultraviolet light converging lens according to claim 1, characterized in that: The object plane is located 109 - 108 mm in front of the object side surface of the first lens, and the object-side numerical aperture is 0.

2.

3. The near-ultraviolet light converging lens for multimode optical fiber according to claim 1, characterized in that: After the light passes through the converging lens for the multimode optical fiber, the converging point is located at the image plane position 198 - 203 mm behind the image side surface of the sixth lens.

4. The multimode optical fiber near-ultraviolet light converging lens according to claim 1, characterized in that: This lens satisfies: 60 < vd1 < 70, 85 < vd2 < 100, 85 < vd3 < 100, 60 < vd4 < 70, 85 < vd5 < 100, 60 < vd6 < 70, where vd1, vd2, vd3, vd4, vd5, vd6 are the dispersion coefficients of the first lens, second lens, third lens, fourth lens, fifth lens, and sixth lens respectively.

5. The near-ultraviolet light converging lens for multimode optical fiber according to claim 1, characterized in that: Satisfies the following conditional expressions: -95 < f1′ < -110, 60 < f2′ < 68, 62 < f3′ < 70, -85 < f4′ < -96, 63 < f5′ < 72, -56 < f6′ < -67, where f1′, f3′, f4′, f5′, f6′ are the focal lengths of the first lens, second lens, third lens, fourth lens, fifth lens, and sixth lens respectively.

6. The multimode optical fiber near-ultraviolet light converging lens according to claim 1, characterized in that: Satisfies the following conditional expressions: 1.40 < nd1 < 1.54, 1.43 < nd2 < 1.50, 1.43 < nd3 < 1.50, 1.40 < nd4 < 1.54, 1.43 < nd5 < 1.50, 1.40 < nd6 < 1.54, where nd1, nd2, nd3, nd4, nd5, nd6 are the refractive indices of the first lens, second lens, third lens, fourth lens, fifth lens, and sixth lens respectively.

7. The near-ultraviolet light converging lens for multimode optical fiber according to claim 1, characterized in that: The focal length f of this lens is 76.823 mm.

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