Near ultraviolet light convergence lens of multimode optical fiber

Abstract

The invention provides a near ultraviolet 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 present invention 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 the optical fiber for transmission. A lens is used to converge the light at the output end of the optical fiber, and the work is realized at the required image convergence point position. After the laser is coupled with the optical fiber, the straight-line transmission path of the light beam can be changed, thereby reducing the limitation of the transmission space, but at the same time there is the problem of low laser to optical fiber coupling efficiency. In order to improve the fiber coupling efficiency, it 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, it is necessary to converge the divergent light beam at the output end of the optical fiber through a converging lens, but increasing the numerical aperture and core diameter of the optical fiber leads to an increase in the aberration of the converging lens, making it difficult to converge the laser. In particular, when converging laser beams of multiple wavelengths and near-ultraviolet wavelengths at the same time, chromatic aberration will make convergence 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 multi-mode optical fiber, the present invention provides a near-ultraviolet light converging lens for a multi-mode optical fiber. Summary of the invention

[0004] The object of the present invention is to provide a converging lens for multimode optical fiber with small converging spot diameter and uniform light energy distribution.

[0005] In order to achieve the above-mentioned object, the present invention adopts the following technical scheme: 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 an object side to an image side, wherein the first lens to the sixth lens each include an object side surface facing the object side and allowing imaging light to pass through, and an image side surface facing the image side and allowing imaging light to pass through;

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

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

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

[0012] Furthermore, in the multimode optical fiber near-ultraviolet light converging lens, when in operation, 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.

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

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

[0015] Furthermore, the lens satisfies the following conditions: -95<f1′<-110, 60<f2′<68, 62<f3′<70, -85<f4′<-96, 63<f5′<72, -56<f6′<-67, wherein f1′, f2′, f3′, f4′, f5′, f6′ are focal length values ​​of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens, respectively.

[0016] Furthermore, the lens satisfies the following conditional formulas: 1.40<ndl<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, wherein ndl, nd2, nd3, nd4, nd5, and nd6 are the refractive indices of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens, respectively.

[0017] Furthermore, the focal length of the lens is f′=76.823 mm.

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

[0019] Figure 1 is a schematic diagram of the lens structure of an embodiment of the present invention;

[0020] Figure 2 A schematic diagram of the optical path operation of an embodiment of the present invention;

[0021] Figure 3 A diagram showing the lens aberration points of an embodiment of the present invention;

[0022] Figure 4 It is a radial energy analysis diagram of an embodiment of the present invention; DETAILED DESCRIPTION

[0023] The present invention provides a multimode optical fiber near-ultraviolet light converging lens, which can be used in conjunction with a multimode optical fiber to converge the divergent light beam emitted by the multimode optical fiber to the image plane position, and its position layout from the multimode optical fiber output end to the converging surface is: multimode optical fiber output end face, lens group, image side converging surface. The multimode optical fiber output end face 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 present invention is further described in detail below in conjunction with the embodiments and drawings. The words "first", "second", "third", "fourth", "fifth", "sixth" and the like 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] The embodiment of the present invention provides a near-ultraviolet light converging lens for a multimode optical fiber, see Figure 1 , which shows the structure of an optical lens provided by an embodiment of the present invention, wherein the optical lens comprises 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 which are arranged in sequence from the object plane to the image plane.

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

[0027] The third lens 3 is a biconvex glass spherical lens with positive power; the fourth lens 4 is a meniscus-shaped glass spherical lens with the concave surface facing the image side and has negative power; the third lens 3 and the fourth lens 2 form a lens group with positive power and satisfy the following conditions: 1.43<nd3<1.50, 1.40<nd4<1.54, 1.43<nd3<1.50, 1.40<nd4<1.54, 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 power respectively, and the third lens 3 and the fourth lens 4 correct chromatic aberration by having different dispersion rates and refractive indices respectively.

[0028] The lens group consisting of the first lens 1 and the second lens 2 and the lens group consisting of the third lens 3 and the fourth lens 4 have a symmetrical structure in shape, thereby further reducing chromatic aberration. Note that the symmetrical 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 positive power; the sixth lens 6 is a biconcave glass spherical lens with negative power; the fifth lens 5 and the sixth lens 6 form a lens group with positive power, and the combined focal length is 6890.6348 mm, and the following conditions are satisfied: 85<vd5<100, 60<vd6<70, 1.43<nd5<1.50, 1.40<nd6<1.54, 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 the spherical aberration by respectively having positive and negative power and respectively having different dispersion rates.

[0030] The near-ultraviolet light focusing lens for multimode optical fiber is described in detail. Figure 2 When in use, the exit surface of the multimode optical fiber is placed 109-108 mm in front of the object side of the first lens 1. This position is the location of the object plane 7 for the converging lens, and its object side aperture angle can reach 0.2.

[0031] The near-ultraviolet light converging lens of a multimode optical fiber, 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 of the sixth lens. This position is 8 for the converging lens where the image plane is located. The image plane is far away from the image side of the sixth lens, is easy to use, and meets the light beam focusing requirements.

[0032] The near-ultraviolet light focusing lens for multimode optical fiber is described in detail. Figure 3The point diagram shows that the numerical aperture of the light 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 near-ultraviolet light focusing lens for multimode optical fiber is described in detail. 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 near-ultraviolet light converging lens for a multimode optical fiber 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 The 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 The sixth lens -53.2 3.5 1.4584 67.79 -61.2818 63.14576 202 Image plane Infinity

Claims

1. A near-ultraviolet light converging lens for a multimode optical fiber, 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 the multimode optical fiber has a working wavelength of 320 - 550 nm.

2. The near-ultraviolet light converging lens for multimode optical fiber 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 near-ultraviolet light converging lens for multimode optical fiber 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: Satisfy the following conditional expressions: -95 < f1′ < -110, 60 < f2′ < 68, 62 < f3′ < 70, -85 < f4′ < -96, 63 < f5′ < 72, -56 < f6′ < -67, where f1′, f2′, f3′, f4′, f5′, f6′ are the focal length values of the first lens, second lens, third lens, fourth lens, fifth lens, and sixth lens respectively.

6. The near-ultraviolet light converging lens of a multimode optical fiber according to claim 1, characterized in that: Satisfy 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.

Images