Optical fiber coupling lens

Abstract

The invention discloses an optical fiber coupling lens, which belongs to the technical field of optical fiber coupling and comprises a front focal plane, a second reflecting mirror, a first reflecting mirror and a rear focal plane along the optical axis direction of the optical fiber coupling lens. Wherein an incident optical fiber is placed at the front focal plane; the focus of the first reflecting mirror is positioned on a front focal plane; emergent light of the optical fiber placed on the front focal plane enters the first reflector after passing through a central hole of the second reflector, is reflected by the first reflector to become parallel light, enters the second reflector, and is reflected and focused by the second reflector; and the rear focal plane is located at the focal plane position of the second reflector, and the light reflected and focused by the second reflector is converged on the rear focal plane of the lens after passing through the central opening of the first reflector. The optical fiber coupling lens system is simple in structure, the manufacturing cost can be effectively reduced, and the processing, detection and adjustment difficulty of the lens is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical fiber coupling, and in particular relates to an optical fiber coupling lens. Background Art

[0002] Fiber-coupled lenses are core optical components in optical communications, laser processing, biomedical testing, semiconductor testing and other fields. Their function is to efficiently couple the light beam output by the light source into the optical fiber, or to achieve low-loss connection between optical fibers, or to modulate the output light of the optical fiber according to the requirements of the subsequent optical system and couple it into the subsequent system.

[0003] Current fiber-coupled lenses typically use lenses as optical components. However, to correct for chromatic aberration or improve coupling efficiency, these lens-based lenses require additional lenses, making the lens structure complex and costly. Furthermore, these lenses are generally only suitable for incident light within a narrow wavelength band. Furthermore, adjusting optical parameters such as the numerical aperture (NA) of the output light to meet the requirements of subsequent optical systems can complicate lens design modifications. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0005] A fiber-coupled lens comprises: a front focal plane along its optical axis, a second reflector, a first reflector, and a back focal plane. The front focal plane is where the incident optical fiber is placed; the first reflector has its focus located at the front focal plane. Light emitted from the optical fiber placed at the front focal plane passes through the central opening of the second reflector and is incident on the first reflector. After reflection from the first reflector, it is converted into parallel light and incident on the second reflector, where it is reflected and focused by the second reflector. The back focal plane is located at the focal plane position of the second reflector. Light reflected and focused by the second reflector passes through the central opening of the first reflector and converges at the back focal plane of the lens.

[0006] The present invention has the following beneficial effects:

[0007] (1) The fiber-coupled lens of the present invention uses two parabolic reflectors as optical elements and can be processed with inexpensive metal materials. Compared with the traditional fiber-coupled lens using multiple lenses, the fiber-coupled lens system of the present invention has a simple structure, which can effectively reduce manufacturing costs and reduce the difficulty of lens processing, detection and adjustment.

[0008] (2) The fiber-coupled lens of the present invention uses a reflector instead of a lens element, has no chromatic aberration, and is applicable to systems in different wavelength ranges, thus overcoming the shortcoming of the traditional fiber-coupled lens that its applicable wavelength range is small.

[0009] (3) The fiber-coupled lens of the present invention can flexibly adjust the NA and obscuration ratio of light entering the subsequent optical system by adjusting the focal length and center opening size of the first reflector and the second reflector, and can more flexibly modify the lens structure and more easily meet the different requirements of the subsequent optical system for the parameters of the light output from the fiber-coupled lens. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 This is the optical path diagram of the fiber-coupled lens of the present invention, where M1 is the first reflector and M2 is the second reflector;

[0011] Figure 2 This is an MTF diagram of the optical modulation transfer function of the fiber-coupled lens of the present invention;

[0012] Figure 3 This is the field curvature and distortion distribution diagram of the fiber-coupled lens of the present invention. DETAILED DESCRIPTION

[0013] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only intended to illustrate the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0014] The present invention provides a fiber-coupled lens, comprising a front focal plane along its optical axis, a second reflector M2, a first reflector M1, and a back focal plane. An incident optical fiber is placed at the front focal plane; both the second reflector M2 and the first reflector M1 are parabolic reflectors; the focus of the first reflector M1 is located at the front focal plane. Light emitted from the optical fiber placed at the front focal plane passes through the central opening of the second reflector M2 and is incident on the first reflector M1. After reflection by the first reflector M1, it is converted into parallel light and incident on the second reflector M2. Reflection and focus are then achieved by the second reflector M2. The back focal plane is located at the focal plane of the second reflector M2. Light focused by reflection from the second reflector M2 passes through the central opening of the first reflector M1 and converges at the back focal plane of the lens. By adjusting the size of the central opening and focal length of the second reflector M2, light with different NAs can be obtained at the back focal plane. By adjusting the size of the central opening of the first reflector M1, the ratio of the central obstruction to the full aperture of the emitted light can be adjusted.

[0015] The first reflector M1 and the second reflector M2 both have a central opening.

[0016] Figure 1This is the optical path diagram of the fiber-coupled lens of the present invention. It uses two reflectors, including, in order from the direction of light beam incidence along the optical axis, the front focal plane, the second reflector M2, the first reflector M1, and the back focal plane. The front focal plane is used to position the optical fiber. Light emitted from the optical fiber passes through the central opening of the second reflector M2 and is incident on the first reflector M1. After reflection from the first reflector M1, it becomes parallel light and is incident on the second reflector M2. It is then reflected and focused by the second reflector M2. The back focal plane is located at the focal plane position of the second reflector M2. The light reflected and focused by the second reflector M2 passes through the central opening of the first reflector M1 and converges at the back focal plane of the lens, coupling into the subsequent optical system.

[0017] In the fiber-coupled lens, both the first reflector M1 and the second reflector M2 are parabolic reflectors with central openings, resulting in a simple system structure. The reflectors can be made of optical glass, metal, or its alloys, effectively reducing manufacturing costs and simplifying lens processing, testing, and assembly.

[0018] The fiber-coupled lens has no chromatic aberration because all its optical components are reflective elements. By selecting different reflector materials, high reflectivity can be achieved for light waves from infrared to ultraviolet. Therefore, it is applicable to systems with different wavelength ranges, greatly expanding the scope of use of the fiber-coupled lens.

[0019] The fiber-coupled lens can flexibly adjust the NA and obscuration ratio of the optical fiber entering the subsequent optical system by adjusting the focal length and central opening size of the first reflector M1 and the second reflector M2, making the fiber-coupled lens applicable to various optical systems and greatly improving its scope of application.

[0020] Table 1 lists the specific parameters of each surface of the fiber-coupled lens of the present invention. The "serial numbers" in the table are arranged in the order in which light passes through them. The beam incident surface of the first reflector M1 is serial number 1, and the beam incident surface of the second reflector M2 is serial number 2. The "radius of curvature" gives the radius of curvature of each vertex corresponding to each surface. If the center of curvature of the vertex is to the left of the vertex, the curvature radius is negative; otherwise, it is positive. If the vertex area of ​​a surface is flat, its curvature radius is recorded as "∞". The "K coefficient" is the quadratic surface coefficient of the surface; the "center spacing" is the center distance along the optical axis between two adjacent surfaces. A negative spacing indicates that the next surface is to the left of the surface.

[0021] Table 1

[0022]

[0023] In actual operation, the specific parameters of the above-mentioned surfaces of the lens, such as curvature radius, K coefficient, center spacing, etc., as well as the materials of the first reflector M1 and the second reflector M2, can be adjusted to meet different system parameter requirements.

[0024] The fiber-coupled lens manufactured in this embodiment was evaluated using the following two evaluation methods:

[0025] 1. Optical Modulation Transfer Function (MTF):

[0026] Figure 2 This is the optical modulation transfer function (MTF) of the fiber-coupled lens manufactured in this embodiment. The optical modulation transfer function (MTF) is used to evaluate the efficiency of transferring images of different spatial frequencies through the optical system to the image plane. The abscissa of the MTF curve is the spatial frequency (in line pairs / mm), and the ordinate is the modulation function. Figure 2 As shown in FIG. 1 , when the object-side field of view height of the fiber-coupled lens manufactured in this embodiment is 0.1 mm, the MTF reaches the diffraction limit, indicating that for optical fibers with a fiber diameter less than 0.2 mm, the fiber-coupled lens manufactured in this embodiment can perfectly image the rear optical system.

[0027] 2. Astigmatism, field curvature and distortion:

[0028] Figure 3 The field curvature and distortion distribution diagram of the fiber-coupled lens produced in this embodiment is shown on the left. The horizontal axis represents the amount of deviation of the image point from the focal plane in different fields of view, and the vertical axis represents the object-side field angle. The dotted line represents the field curvature of the image point on the sagittal plane, and the solid line represents the field curvature of the image point on the meridian plane. The difference between the dotted and solid lines is the astigmatism of the image point. The right side is a schematic diagram of the distortion distribution, with the horizontal axis representing the distortion amount and the vertical axis representing the object-side field angle. Figure 3 It can be seen that the field curvature and astigmatism of the fiber-coupled lens manufactured in this embodiment are controlled within 0.02 mm, and the maximum field distortion is about 0.01%.

[0029] In summary, all optical elements included in the fiber-coupled lens of the present invention are parabolic reflectors. The reflector material can be optical glass, metal, or its alloy, which can effectively reduce manufacturing costs and reduce the difficulty of lens processing, testing, and adjustment. The reflective elements have no chromatic aberration, and different reflector materials can be selected to obtain high reflectivity for light waves from infrared to ultraviolet, which is applicable to systems with different wavelength ranges and can achieve high coupling efficiency. In addition, by adjusting the focal length and central opening size of the first reflector M1 and the second reflector M2, the fiber-coupled lens can flexibly adjust the NA and obscuration ratio of the subsequent optical system, making the fiber-coupled lens applicable to various optical systems, greatly improving its scope of application.

[0030] The above descriptions are merely embodiments of the present invention and are not intended to limit the scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention description and drawings, or directly or indirectly applied to other related system fields, are also included in the scope of protection of the present invention.

[0031] The contents not described in detail in the specification of the present invention belong to the prior art known to those skilled in the art.

Claims

1. A fiber-coupled lens, characterized in that: include: A front focal plane, a second reflector, a first reflector, and a back focal plane are arranged along the optical axis; an incident optical fiber is placed at the front focal plane; the first reflector has a focus located at the front focal plane; light emitted from the optical fiber placed at the front focal plane passes through the central opening of the second reflector and is incident on the first reflector. After being reflected by the first reflector, the light is converted into parallel light and is incident on the second reflector, where it is reflected and focused by the second reflector. The rear focal plane is located at the focal plane position of the second reflector. The light reflected and focused by the second reflector passes through the central opening of the first reflector and converges on the rear focal plane of the lens.

2. The fiber-coupled lens according to claim 1, wherein: By adjusting the size of the central opening and the focal length of the second reflector M2, outgoing light with different numerical apertures can be obtained at the rear focal plane.

3. The fiber-coupled lens according to claim 1, wherein: By adjusting the size of the central opening of the first reflector M1, the ratio of the central obstruction to the full aperture of the outgoing light is adjusted.

4. The fiber-coupled lens according to claim 1, wherein: The first reflector and the second reflector are both parabolic reflectors.

5. The fiber-coupled lens according to claim 1, wherein: The first reflector and the second reflector are made of optical glass.

6. The fiber-coupled lens according to claim 1, wherein: The first reflector and the second reflector are made of metal.

7. The fiber-coupled lens according to claim 1, wherein: The first reflector and the second reflector are made of metal alloy.

8. The fiber-coupled lens according to claim 1, wherein: The central opening size and focal length of the first reflector and the second reflector are adjusted, and the numerical aperture and obscuration ratio of the lens entering the subsequent optical system are adjusted, so that the fiber coupling lens is applicable to different optical systems.

9. The fiber-coupled lens according to claim 1, wherein: The parameters of the object plane, the beam incident plane of the first reflector, the beam incident plane of the second reflector, the image plane and the material of the lens are adjusted to meet different system parameter requirements.

10. The fiber-coupled lens according to claim 9, wherein: The parameters of the object plane, the light beam incident surface of the first reflector, the light beam incident surface of the second reflector, and the image plane are the curvature radius, the K coefficient, and the center interval.

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