A flat-field conversion system for lobster-eye lenses

Abstract

The present invention discloses a flat-field conversion system for a lobster-eye lens, which belongs to the field of detection. The present invention comprises a light source, a lobster-eye lens, a curved optical fiber bundle, a relay lens group, a medium-wave infrared detector, and a base. The lobster-eye lens is used to receive light projected by a detection object within the field of view. The present invention places the light source at the edge of the field of view of the lobster-eye lens, and the lobster-eye lens, the curved optical fiber bundle, the relay lens group, and the medium-wave infrared detector are coaxially fixed on the base in sequence from left to right. The lobster-eye lens detects objects in the edge of the field of view, and the medium-wave infrared light emitted by the object is converged on the front end surface of the curved optical fiber bundle through the lobster-eye lens and forms an image. The curved optical fiber bundle converts the curved image plane into a flat field and transmits it to the object plane of the relay lens group. The relay lens group transmits the image plane and performs cold stop matching with the medium-wave infrared detector, thereby resolving the contradiction between the large field of view and high resolution of the lobster-eye lens, and realizing high-precision detection of targets in the edge of the field of view by the lobster-eye system.

Description

Technical Field

[0001] The invention belongs to the field of detection and relates to a flat field conversion system for a lobster eye lens. Background Art

[0002] Bionic lobster eye lens ( Figure 1 ) consists of several microchannels forming a square plane. According to the structure of the microchannels, it is divided into two types: Schmidt type and Angle type. Different from the traditional imaging optical system with large field of view and high resolution, the bionic lobster eye lens has the characteristics of small size and low manufacturing cost, which solves the problems of large size, multiple lenses and high cost of traditional imaging optical systems. The lobster eye optical system is more used in visible light and infrared bands. The lobster eye optical system is a reflective optical system ( Figure 2 ), there is no problem of material band characteristics, and wide spectrum, common aperture, large field of view, and high-resolution target detection and imaging can be achieved. The bionic lobster eye technology has good application prospects in seeker guidance.

[0003] However, the spherically symmetrical structure of the lobster-eye lens, formed by the rectangular microchannel plate, while widening the field of view, also results in a curvature of the image plane. Currently used detectors are mostly planar structures. The greater the target's off-axis angle, the greater the deviation between the detector's actual detection position and the image plane position, and the more diffuse the focal spot. This limits further expansion of the lobster-eye lens's field of view, weakening its wide-field detection capabilities.

[0004] With the continuous development of fiber bundle imaging, the preparation of curved fiber bundles has come into people's field of vision. Figure 3 By coupling with the curved focal plane, optical signals are independently transmitted along their respective fiber channels, ultimately becoming flat fields upon reaching the output end face. Applying curved fiber bundles to lobster-eye imaging systems largely preserves the wide field of view of the lobster-eye lens, transforming the curved image plane into a flat field that is received by the detector, producing clear images even at the edges of the field of view. Summary of the Invention

[0005] In order to solve the problem that the image of the target at the edge of the lobster-eye lens has large diffuse spots and is difficult to detect accurately, the purpose of the present invention is to provide a flat-field conversion system for the lobster-eye lens. Based on the flat-field conversion system, the edge of the lobster-eye lens can be clearly imaged, and small objects in the edge of the lobster-eye lens can be accurately positioned.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] The invention discloses a flat-field conversion system for a lobster-eye lens, comprising a light source, a lobster-eye lens, a curved optical fiber bundle, a relay lens group, a medium-wave infrared detector and a base.

[0008] The curvature radius of the lobster eye lens ranges from 100 to 800 mm, the focal length is half of the curvature radius of the lobster eye lens, the curvature radius of the imaging surface is equal to the focal length, the field of view range is 20° to 60°, and the lobster eye lens is used to receive light projected by the detection object within the field of view.

[0009] The curved fiber bundle is coupled to the image plane of the lobster-eye lens. A curved fiber bundle with a front facet curvature radius equal to the curvature radius of the lobster-eye lens image plane and a numerical aperture range of 0.3 to 0.7 is selected, and the center of the front facet is placed at the focal point of the central field of view of the lobster-eye lens. The curved fiber bundle is used to convert the curved image plane of the lobster-eye lens into a flat image.

[0010] The relay lens group has an object-side numerical aperture of 0.3 to 0.7 (equal to the numerical aperture of the curved fiber bundle) and includes one or more concave lenses or convex lenses. The relay lens group is used to adjust the light output by the curved fiber bundle to achieve cold stop matching of the medium-wave infrared detector. On this basis, the image plane of the lobster-eye lens is completely imaged on the medium-wave infrared detector.

[0011] The medium-wave infrared detector can detect medium-wave infrared light with a wavelength of 3 to 5 μm. The medium-wave infrared detector is used to receive an image output by the relay lens group after proportionally magnifying the plane image output by the curved optical fiber bundle located at the object surface of the relay lens.

[0012] The light source is placed at the edge of the lobster-eye lens's field of view. The lobster-eye lens, curved fiber bundle, relay lens assembly, and medium-wave infrared detector are coaxially fixed to the base from left to right. The curved fiber bundle includes one or more optical fibers. The relay lens assembly includes one or more convex lenses or one or more concave lenses.

[0013] Furthermore, the lobster-eye lens is a square plane composed of several micro-matrix channels. After entering the lobster eye, light is reflected by the tiny matrix channels and converges to a focal point. Because the structure of the lobster-eye lens has the characteristic of independently converging light in two perpendicular directions, the focusing effect is not completely concentrated, but instead exhibits a unique "cross focal spot" phenomenon.

[0014] Furthermore, the aspect ratio of the lobster eye (the ratio of its length t to its channel width d) satisfies:

[0015]

[0016] where θ c is the critical grazing incidence angle. ε is a constant close to 1. Preferably, the optimal value of the constant ε is ε≈0.85.

[0017] Furthermore, when the lobster-eye lens receives parallel light from the central field of view, it passes through the lens and undergoes a single reflection before emerging at the focal point. At this point, the light rotates by an angle of 2θ, where θ is the axial angle of a single subchannel of the lobster-eye lens. The outgoing light, the straight line along the channel wall from which the light is reflected by a single subchannel, and the optical axis form an isosceles triangle. When the parallel light passes through the center of the lobster-eye lens and converges to the focal point after a single reflection, θ approaches 0. The two sides of the isosceles triangle approximately coincide with the base (the radius of curvature R of the lobster-eye lens), so the focal length of the lobster-eye lens is always equal to half of its radius of curvature R. Within the field of view, since parallel light incident at different angles converges on the focal plane, the image is always formed at a distance R / 2 from the lobster-eye lens, meaning that the image plane is a spherical surface with a radius of R / 2.

[0018] Furthermore, the front end face of the curved optical fiber bundle has a curvature that is the same as the curvature radius of the lobster-eye image plane, and the center of the front end face of the curved optical fiber bundle is located at the focal point of the central field of view of the lobster-eye lens.

[0019] Furthermore, the curved optical fiber bundle has a numerical aperture equal to the maximum numerical aperture of the image side of the lobster eye lens, thereby avoiding a large amount of energy loss caused by coupling the curved optical fiber bundle with the image plane of the lobster eye lens.

[0020] Furthermore, the magnification of the relay lens group is β, and the magnification β enables the image plane transmitted by the zoomed curved light beam to be completely imaged on the medium-wave infrared detector.

[0021] The present invention discloses a flat-field conversion system for a lobster-eye lens. The system employs the following operating method: a light source is placed at the edge of the lobster-eye lens's field of view. The lobster-eye lens, curved fiber bundle, relay lens assembly, and medium-wave infrared detector are coaxially fixed to a base in order from left to right. The lobster-eye lens detects objects in the edge of the field of view. The medium-wave infrared light emitted by the object passes through the lobster-eye lens and converges onto the front face of the curved fiber bundle, forming a primary image. The curved fiber bundle converts the curved image plane into a flat field and transmits it to the object plane of the relay lens assembly. The relay lens assembly transmits the image plane and performs cold-block matching with the medium-wave infrared detector. This resolves the contradiction between the lobster-eye lens's large field of view and high resolution, enabling the lobster-eye system to detect objects in the edge of the field of view with high precision.

[0022] Beneficial effects:

[0023] 1. The present invention discloses a flat-field conversion system for lobster-eye lenses. This system extends the lobster-eye lens system by using a curved fiber bundle without changing the lens's structure. Compared with methods that directly design the optical path for the lobster-eye lens, this system is easier to design, process, and assemble, making mass production of lobster-eye lens systems possible.

[0024] 2. The present invention discloses a flat-field conversion system for a lobster-eye lens. By coupling a curved fiber bundle with the curved image plane of the lobster-eye lens, the system solves the problem of the lobster-eye lens having a curved image plane when imaging at the edge of the field of view, which makes it difficult to directly couple with a flat detector, resulting in a large diffuse focal spot. This improves the lobster-eye optical system's ability to accurately detect targets at the edge of the field of view.

[0025] 3. The present invention discloses a flat-field conversion system for lobster-eye lenses. It uses a relay lens group to receive the flat image output by the curved fiber bundle, transmits the image plane, and matches the cold filter with the medium-wave infrared detector. This solves the problem that the fiber bundle can only be coupled with the medium-wave infrared detector without a cold filter in the medium-wave infrared band, and broadens the scope of application of the fiber bundle in the medium-wave infrared band optical system.

[0026] 4. This invention discloses a flat-field conversion system for lobster-eye lenses. This system couples the lobster-eye lens's large-field-of-view, high-resolution image plane with significant field curvature to an image-transmitting fiber bundle with a curved front end and the same curvature as the image plane. This curved fiber bundle transmits light and converts the lobster-eye lens's curved image plane into a flat surface. This system enables clear imaging and accurate detection of targets at the edge of the field of view. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the lobster eye lens structure.

[0028] Figure 2 This is the principle of reflective imaging of the lobster eye lens (cross section).

[0029] Figure 3 Schematic diagram of curved fiber bundle.

[0030] Figure 4 Schematic diagram of the flat-field conversion system for lobster-eye lenses.

[0031] Figure 5 Schematic diagram of imaging through a lobster eye lens.

[0032] Figure 6 Schematic diagram of the device of the present invention.

[0033] Figure 7 (a) is a schematic diagram of the edge field imaging of the lobster eye lens. Figure 7 (b) Schematic diagram of edge field imaging of the flat-field conversion system for the lobster-eye lens.

[0034] Among them, 1- lobster eye lens, 2- curved fiber bundle, 3- relay lens group, 4- medium wave infrared detector, 5- lobster eye lens, 6- curved fiber bundle, 7- relay lens group, 8- medium wave infrared detector. DETAILED DESCRIPTION

[0035] In order to better illustrate the purpose and advantages of the present invention, the invention is further described below with reference to the accompanying drawings and examples.

[0036] Example 1:

[0037] The imaging method of lobster eye lens is different from that of other traditional transmissive compound eyes. After the light enters the lobster eye, it is reflected through the tiny channels and converges to the focus (such as Figure 5 ). Since the structure of the lobster-eye lens has the characteristic of independently converging light in two perpendicular directions, its focusing effect is not completely concentrated, but presents a special "cross focal spot" phenomenon. Within the field of view, the image of the lobster eye is always formed at a distance of R / 2 from the lobster-eye lens, that is, the image plane is a sphere with O as the center and R / 2 as the radius. Therefore, the focal length of the lobster eye is defined as f=R / 2. When light passes through the lobster-eye lens, it is reflected through a tiny channel and forms a "cross focal spot" on the image plane. The energy is mainly concentrated in the center of the "cross focal spot", and a small part is dispersed in the cross focal arms. However, in the edge field of view, the central bright spot of the "cross focal spot" is diffused, mainly because the lobster-eye image plane has a large field curvature.

[0038] like Figure 4 As shown, this embodiment discloses a flat-field conversion system for a lobster-eye lens, comprising a lobster-eye lens 1, a curved optical fiber bundle 2, a relay lens group 3 and a medium-wave infrared detector 4.

[0039] The lobster eye lens 1 has a curvature radius of 100 mm, a focal length of 50 mm, a curvature radius of the curved image plane of 50 mm, and a field of view of 20°.

[0040] In order to couple with the image plane of the lobster-eye lens 1 , the curved optical fiber bundle 2 is selected to have a front face curvature radius of 50 mm and a numerical aperture of 0.5, and the center of the front face is placed at the focus of the lobster-eye lens 1 .

[0041] The relay lens group 3 is an infrared relay lens with a zoom ratio of 1:1, which forms a 1:1 image of the image transmitted by the curved optical fiber bundle 2 on the medium-wave infrared detector 4.

[0042] The medium-wave infrared detector 4 is an antimonide medium-wave infrared detector, and the distance between the window of the medium-wave infrared detector 4 and the detector chip is 30 mm.

[0043] Functions of each component:

[0044] The lobster eye lens 1 is used to receive light projected by a detection object within the field of view.

[0045] The curved optical fiber bundle 2 is used to convert the curved image surface of the lobster-eye lens into a flat image.

[0046] The relay lens group 3 is used to adjust the light so that it matches the cold filter of the medium-wave infrared detector 4 .

[0047] The relay lens group 3 is used to enlarge the image plane of the curved light beam so that the image is completely formed on the medium-wave infrared detector 4 .

[0048] The medium-wave infrared detector 4 is used to receive the image of the system.

[0049] The working method of a flat-field conversion system for a lobster-eye lens disclosed in this embodiment is as follows:

[0050] like Figure 6 As shown, a lobster-eye lens 1, a curved fiber bundle 2, a relay lens assembly 3, and a medium-wave infrared detector 4 are coaxially fixed to a base from left to right, with a light source placed at the edge of the field of view of lobster-eye lens 1. Lobster-eye lens 1 detects objects at the edge of the field of view. The medium-wave infrared light emitted by the object passes through the lobster-eye lens and converges on the front face of the curved fiber bundle 2, forming a primary image. The curved fiber bundle 2 converts the curved image plane into a flat field and transmits it to the object plane of relay lens assembly 3. Relay lens assembly 3 transmits the image plane in a 1:1 ratio and performs cold-block matching with medium-wave infrared detector 4. This resolves the contradiction between the lobster-eye lens's large field of view and high resolution, enabling the lobster-eye system to accurately detect targets at the edge of the field of view.

[0051] like Figure 7 (a) shows the schematic diagram of the imaging of the edge field of view of the lobster eye lens. The "cross focal spot" on the image plane is diffuse and the energy is not concentrated. Figure 7 (b) The edge field imaging of the flat-field conversion system for the lobster-eye lens. The diffusion of the "cross focal spot" is reduced, and a clear "cross focal arm" appears. The position of the object can be detected through the clear "cross focal arm".

[0052] The above specific description further illustrates the purpose, technical solutions and beneficial effects of the invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A flat-field conversion system for lobster-eye lenses, characterized by: It includes a light source, a lobster-eye lens, a curved optical fiber bundle, a relay lens assembly, a medium-wave infrared detector, and a base; The lobster eye lens has a curvature radius ranging from 100 to 800 mm, a field of view ranging from 20° to 60°, a focal length equal to half the curvature radius of the lobster eye lens, and a curvature radius of the imaging surface equal to the focal length. The lobster eye lens is used to receive light projected by a detection object within the field of view. The curved optical fiber bundle is coupled to the image plane of the lobster-eye lens, and a curved optical fiber bundle with a front face curvature radius equal to the curvature radius of the image plane of the lobster-eye lens and a numerical aperture range of 0.3 to 0.7 is selected, and the center of the front face is placed at the focal point of the central field of view of the lobster-eye lens; the curved optical fiber bundle is used to convert the curved image plane of the lobster-eye lens into a flat image; The relay lens assembly has an object-side numerical aperture of 0.3 to 0.7 and includes one or more concave or convex lenses. The relay lens assembly is used to adjust the light output by the curved optical fiber bundle to achieve cold stop matching of the medium-wave infrared detector. On this basis, the image plane of the lobster-eye lens is completely imaged on the medium-wave infrared detector. The medium-wave infrared detector detects medium-wave infrared light with a wavelength of 3 to 5 μm, and is used to receive an image output after the relay lens group proportionally magnifies the plane image output by the curved optical fiber bundle located at the object surface of the relay lens; The light source is placed at the edge of the lobster-eye lens's field of view. The lobster-eye lens, curved optical fiber bundle, relay lens group, and medium-wave infrared detector are coaxially fixed on the base from left to right.

2. The flat-field conversion system for lobster-eye lenses according to claim 1, characterized in that: The curved optical fiber bundle includes more than one optical fiber; the relay lens group includes more than one convex lens or more than one concave lens.

3. A flat-field conversion system for a lobster-eye lens according to claim 1 or 2, characterized in that: The lobster-eye lens is a square plane composed of several tiny matrix channels. After entering the lobster eye, light is reflected by the tiny matrix channels and converges to a focal point. Due to the structure of the lobster-eye lens having the characteristic of independently converging light in two perpendicular directions, its focusing effect is not completely concentrated, but presents a "cross focal spot".

4. A flat-field conversion system for a lobster-eye lens according to claim 1 or 2, characterized in that: When the lobster-eye lens receives parallel light from the central field of view, it passes through the lens and undergoes a single reflection before emerging at the focal point. At this point, the light rotates by an angle of 2θ, where θ is the axial angle of a single sub-channel of the lobster-eye lens. The outgoing light, the straight line along the channel wall reflecting the light from the single sub-channel, and the optical axis form an isosceles triangle. When the parallel light passes through the center of the lobster-eye lens and converges to the focal point after a single reflection, θ approaches 0. The two waists and base of the isosceles triangle approximately coincide with each other, so the focal length of the lobster-eye lens is always equal to half of its radius of curvature, R. Within the field of view, parallel light incident at different angles will converge on the focal plane and form an image, which is always formed at a distance of R / 2 from the lobster-eye lens. This means that the image plane is a sphere with a radius of R / 2.

5. The flat-field conversion system for lobster-eye lenses according to claim 1 or 2, characterized in that: The aspect ratio of the lobster eye satisfies: where θ c is the critical grazing incidence angle; ε is a constant close to 1.

6. The flat-field conversion system for lobster-eye lenses according to claim 5, characterized in that: The optimal value of the constant ε is ε≈0.

85.

7. The flat-field conversion system for lobster-eye lenses according to claim 1 or 2, characterized in that: The front end face of the curved optical fiber bundle has a curvature that is the same as the curvature radius of the lobster-eye image plane, and the center of the front end face of the curved optical fiber bundle is located at the focal point of the central field of view of the lobster-eye lens.

8. The flat-field conversion system for lobster-eye lenses according to claim 1 or 2, characterized in that: The curved fiber bundle has a numerical aperture equal to the maximum numerical aperture of the image side of the lobster eye lens, thereby avoiding a large amount of energy loss caused by coupling the curved fiber bundle with the image plane of the lobster eye lens.

9. The flat-field conversion system for lobster-eye lenses according to claim 1 or 2, characterized in that: The magnification of the relay lens group is β, and the magnification β enables the image plane transmitted by the curved light beam to be completely imaged on the medium-wave infrared detector.

10. The flat-field conversion system for lobster-eye lenses according to claim 1 or 2, characterized in that: The light source is placed at the edge of the lobster-eye lens's field of view. The lobster-eye lens, curved fiber bundle, relay lens group, and medium-wave infrared detector are coaxially fixed on the base from left to right. The lobster-eye lens detects objects in the edge of the field of view. The infrared radiation energy emitted by the object converges on the front end surface of the curved fiber bundle and forms an image. The curved fiber bundle converts the curved image plane into a flat field and transmits it to the object plane of the relay lens group. The relay lens group transmits the image plane and performs cold-stop matching with the medium-wave infrared detector, enabling the lobster-eye system to detect targets at the edge of the field of view with high precision.

Images