A low-distortion mapping lens

Abstract

This invention discloses a low-distortion mapping lens, comprising, from the object side to the image side, a first lens with negative optical power, a second and third lens with positive optical power, a fourth, fifth, and sixth lens with negative optical power, a seventh and eighth lens with positive optical power, and a ninth lens with negative optical power; the fourth and fifth lenses form a first cemented lens group, and the sixth and seventh lenses form a second cemented lens group. This invention further reduces optical distortion and can be widely applied in the field of optical device technology.

Description

Technical Field

[0001] This invention relates to the field of optical device technology, and in particular to a low-distortion mapping lens. Background Technology

[0002] In surveying work, lens distortion can affect the accuracy of measurements, especially in applications requiring high-precision measurements. Surveying lenses are very sensitive to distortion, and currently, the optical distortion of surveying lenses cannot meet the requirements of these applications. Summary of the Invention

[0003] In view of this, in order to solve one of the above problems, the purpose of this invention is to provide a low-distortion mapping lens that can further reduce optical distortion.

[0004] This invention provides a low-distortion mapping lens, which, from the object side to the image side, sequentially includes a first lens with negative optical power, a second and a third lens with positive optical power, a fourth, a fifth, and a sixth lens with negative optical power, a seventh and an eighth lens with positive optical power, and a ninth lens with negative optical power; the fourth and fifth lenses form a first cemented lens group, and the sixth and seventh lenses form a second cemented lens group.

[0005] Optionally, the full field of view of the lens satisfies the following relationship:

[0006] 45°<2θ<65°

[0007] Where 2θ represents the full field of view of the lens.

[0008] Optionally, the total length of the lens and the image plane size of the lens satisfy the following relationship:

[0009] 2 <T / h<3.5

[0010] Where T represents the total length of the lens, and h represents the image plane size of the lens.

[0011] Optionally, the incident angle of the principal ray of the lens satisfies the following relationship:

[0012] 20 <CRA<26

[0013] CRA indicates the angle of incidence of the principal ray from the lens.

[0014] Optionally, the optical back focal length of the lens and the total length of the lens satisfy the following relationship:

[0015] 0.12 <BFL / T<0.3

[0016] Where BFL represents the optical back focal length of the lens, and T represents the total length of the lens.

[0017] Optionally, any one or more of the materials used in the first to the ninth lenses include spherical glass.

[0018] Optionally, the refractive index and Abbe number of the first lens satisfy the following relationship:

[0019] 1.45 <N1<1.6

[0020] 63 <V1<65

[0021] Where N1 represents the refractive index of the first lens and V1 represents the Abbe number of the first lens.

[0022] Optionally, the refractive index of the third lens satisfies the following relationship:

[0023] 1.8 <N3<2.1

[0024] Where N3 represents the refractive index of the third lens.

[0025] Optionally, the refractive index of the eighth lens satisfies the following relationship:

[0026] 1.85 <N8<2.05

[0027] N8 represents the refractive index of the eighth lens.

[0028] Optionally, the focal length of the lens satisfies the following relationship:

[0029] 35 <f<45

[0030] Where f represents the focal length of the lens.

[0031] Implementing the embodiments of the present invention has the following beneficial effects: In this embodiment, the low-distortion mapping lens includes nine lenses, including two sets of cemented lens groups. The incident light passes through the first lens to compress and correct chromatic aberration, the third lens to control aberration, the first and second cemented lens groups to further correct chromatic aberration, and the eighth lens to further control aberration, thereby further reducing optical distortion and controlling optical distortion to within 0.2%. In addition, the lens is small and lightweight, optimizing the quality and size of the lens. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the structure of a low-distortion mapping lens provided in an embodiment of the present invention;

[0033] Figure 2 This is an aberration map of a low-distortion mapping lens provided in an embodiment of the present invention;

[0034] Figure 3 This is a field curvature diagram of a low-distortion mapping lens provided in an embodiment of the present invention;

[0035] Figure 4 This is a peripheral brightness map of a low-distortion mapping lens provided in an embodiment of the present invention;

[0036] Figure 5 This is a distortion map of a low-distortion mapping lens provided in an embodiment of the present invention;

[0037] Figure 6 This is an aberration diagram of another low-distortion mapping lens provided in an embodiment of the present invention;

[0038] Figure 7 This is a field curvature diagram of another low-distortion mapping lens provided in an embodiment of the present invention;

[0039] Figure 8 This is a peripheral brightness map of another low-distortion mapping lens provided in an embodiment of the present invention;

[0040] Figure 9 This is a distortion map of another low-distortion mapping lens provided in an embodiment of the present invention. Detailed Implementation

[0041] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. The step numbers in the following embodiments are only for ease of explanation and do not limit the order of the steps. The execution order of each step in the embodiments can be adapted according to the understanding of those skilled in the art.

[0042] like Figure 1 As shown, this embodiment of the invention provides a low-distortion mapping lens, which, from the object side to the image side, sequentially includes a first lens L1 with negative optical power, a second lens L2 and a third lens L3 with positive optical power, a fourth lens L4, a fifth lens L5 and a sixth lens L6 with negative optical power, a seventh lens L7 and an eighth lens L8 with positive optical power, and a ninth lens L9 with negative optical power; the fourth lens L4 and the fifth lens L5 form a first cemented lens group, and the sixth lens L6 and the seventh lens L7 form a second cemented lens group.

[0043] Specifically, see Figure 1The first lens L1 has a convex object-side surface S1 and a concave image-side surface S2. It is made of low-refractive-index, high-Abbe-number glass to reduce light and correct chromatic aberration. The second lens L2 has a convex object-side surface S3 and a concave image-side surface S4. It is made of crown glass. The third lens L3 has a convex object-side surface S5 and a concave image-side surface S6. The fourth lens L4 has a flat object-side surface S7 and a concave image-side surface S8. The fifth lens L5 has a convex object-side surface S9. The fourth lens L4 is cemented with the fifth lens L5, which helps to correct chromatic aberration. The sixth lens L6 has a concave object-side surface S10 and a convex image-side surface S11. The seventh lens L7 has a convex object-side surface S12. The sixth lens L6 is cemented with the seventh lens L7. The eighth lens L8 has a convex object-side surface S13 and a convex image-side surface S14. The ninth lens L9 has a concave object-side surface S15 and a convex image-side surface S14. The first and second cemented lens groups effectively correct chromatic aberration.

[0044] The selection of glass material for the lens, the requirements for the coating, and the design of the internal black object mechanism all effectively control glare suppression.

[0045] Optionally, the full field of view of the lens satisfies the following relationship:

[0046] 45°<2θ<65°

[0047] Where 2θ represents the full field of view of the lens.

[0048] The field of view (FOV) is a crucial concept in optical engineering, determining the field of view of an optical instrument. The size of the FOV directly impacts the performance and application scenarios of optical equipment. A larger FOV results in a wider field of view, but the optical magnification will decrease accordingly. Simply put, when the size of the target object exceeds the FOV, part of the object will not be fully captured by the lens.

[0049] Optionally, the total length of the lens and the image plane size of the lens satisfy the following relationship:

[0050] 2 <T / h<3.5

[0051] Where T represents the total length of the lens, and h represents the image plane size of the lens.

[0052] The total length of a lens refers to the distance from the first surface of the lens to the image plane, reflecting the length of the internal optical components of the lens.

[0053] Optionally, the incident angle of the principal ray of the lens satisfies the following relationship:

[0054] 20 <CRA<26

[0055] CRA indicates the angle of incidence of the principal ray from the lens.

[0056] The angle of incidence of the principal ray is the angle between the incident ray and the normal to the lens surface when the ray enters the lens. In optics, the angle of incidence is the angle between the incident ray and the normal to the incident surface, and the angle of reflection is equal to the angle of incidence. When light enters the lens, it undergoes reflection and refraction at the lens surface. The smaller the angle of incidence, the more light energy is transmitted and the less light energy is reflected. Therefore, the smaller the angle of incidence of the principal ray, the higher the image sharpness. To reduce reflected light energy, an "anti-reflective coating" is usually applied to the lens surface, which increases transmitted light energy and improves image quality.

[0057] Optionally, the optical back focal length of the lens and the total length of the lens satisfy the following relationship:

[0058] 0.12 <BFL / T<0.3

[0059] Where BFL represents the optical back focal length of the lens, and T represents the total length of the lens.

[0060] Optical back focal length (BFL) is defined as the distance from the last surface of a lens in an optical system to the image plane. Several factors need to be considered when determining BFL, including the lens's focal length, aperture size, and lens design. A well-designed BFL ensures that light is correctly focused onto the image plane, thus improving image quality. Furthermore, adjusting the BFL can affect the overall length and weight of the system, which is particularly important for the design of portable devices.

[0061] Optionally, any one or more of the materials used in the first to the ninth lenses include spherical glass.

[0062] Spherical glass can focus more uniformly, reduce aberrations, and thus improve image quality. Compared with flat glass, spherical glass can better correct light refraction, reduce distortion and blurring, and make the image clearer and more realistic.

[0063] Optionally, the refractive index and Abbe number of the first lens satisfy the following relationship:

[0064] 1.45 <N1<1.6

[0065] 63 <V1<65

[0066] Where N1 represents the refractive index of the first lens and V1 represents the Abbe number of the first lens.

[0067] The low refractive index and high Abbe number of the first lens can further reduce light and correct chromatic aberration.

[0068] Optionally, the refractive index of the third lens satisfies the following relationship:

[0069] 1.8 <N3<2.1

[0070] Where N3 represents the refractive index of the third lens.

[0071] The third lens uses a high refractive index material, which can further and more effectively control aberrations.

[0072] Optionally, the refractive index of the eighth lens satisfies the following relationship:

[0073] 1.85 <N8<2.05

[0074] N8 represents the refractive index of the eighth lens.

[0075] The eighth lens uses a high refractive index material, which can further and more effectively control aberrations.

[0076] Optionally, the focal length of the lens satisfies the following relationship:

[0077] 35 <f<45

[0078] Where f represents the focal length of the lens.

[0079] focal length length Field of view aperture 40mm 65mm 57° F5.6

[0080] The focal length of the lens is determined based on the actual application, and this embodiment does not impose specific limitations. In one specific embodiment, the lens has a focal length of 40mm, an optical length of 65mm, a field of view of 57°, and an aperture of F5.6. The lens has a built-in aperture and shutter, which can be adjusted according to different ambient light conditions to achieve good imaging results. In this embodiment, the pixel count can reach 60 megapixels.

[0081] The low-distortion mapping lens of this application is illustrated below with two specific embodiments.

[0082] Example 1

[0083] The structural parameters of the low-distortion mapping lenses are shown in Table 1, and the focal length and capability values ​​of each lens are shown in Table 2. Wherein, OBJ: object plane, STO: aperture, IMA: image plane, R: radius of curvature, D: distance from one surface to the next, N: lens refractive index, and V: lens Abbe number.

[0084] Table 1

[0085]

[0086]

[0087] Table 2

[0088]

[0089] The aberrations, field curvature, peripheral brightness ratio, and distortion of a low-distortion mapping lens are as follows: Figures 2-5 Specifically, Figures 2-5 The wavelength of the medium curve is 435nm-650nm. Figure 2 Intermediate aberrations are controlled within the range of -2μm to 4μm. Figure 3 The meridional field curvature and sagittal field curvature are controlled within the range of -0.2mm to 0.2mm; because surveying requires strict distortion control, lens distortion is controlled within 0.2%. Figure 4 The peripheral light ratio of the lens is not less than 40% at an image height of 21.5mm; Figure 5 The Airy disk in the center field of view of the midpoint array diagram is controlled within 1.5 μm. Figures 2-5 The results show that the lens can accurately reproduce proportions, with minimal distortion and good color correction in surveying and mapping.

[0090] Example 2

[0091] The structural parameters of the low-distortion mapping lenses are shown in Table 3, and the focal length and capability values ​​of each lens are shown in Table 4. Wherein, OBJ: object plane, STO: aperture, IMA: image plane, R: radius of curvature, D: distance from one surface to the next, N: lens refractive index, and V: lens Abbe number.

[0092] Table 3

[0093]

[0094]

[0095] Table 4

[0096]

[0097]

[0098] The aberrations, field curvature, peripheral brightness ratio, and distortion of a low-distortion mapping lens are as follows: Figures 6-9 Specifically, Figures 6-9 The wavelength of the medium curve is 435nm-650nm; Figure 6 Intermediate aberrations are controlled within the range of (-2μm to 4μm); Figure 7 The meridional field curvature and sagittal field curvature are controlled within the range of (-0.2mm to 0.2mm); because surveying requires strict distortion control, lens distortion is controlled within 0.2%. Figure 8 The peripheral light ratio of the lens is not less than 40% at an image height of 21.5mm; Figure 9 The Airy disk in the center field of view of the midpoint array diagram is controlled within 1.5 μm. Figures 6-9 The results show that the lens can accurately reproduce proportions, with minimal distortion and good color correction in surveying and mapping.

[0099] Implementing the embodiments of the present invention has the following beneficial effects: In this embodiment, the low-distortion mapping lens includes nine lenses, including two sets of cemented lens groups. The incident light passes through the first lens to compress and correct chromatic aberration, the third lens to control aberration, the first and second cemented lens groups to further correct chromatic aberration, and the eighth lens to further control aberration, thereby further reducing optical distortion and controlling optical distortion to within 0.2%. In addition, the lens is small and lightweight, optimizing the quality and size of the lens.

[0100] The above is a detailed description of the preferred embodiments of the present invention. However, the present invention is not limited to the embodiments described. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention. All such equivalent modifications or substitutions are included within the scope defined by the claims of this application.

Claims

1. A low-distortion mapping lens, characterized in that, From the object side to the image side, the lens comprises, in sequence, a first lens with negative optical power, a second lens with positive optical power, a third lens with positive optical power, a fourth lens with negative optical power, a fifth lens with negative optical power, a sixth lens with negative optical power, a seventh lens with positive optical power, an eighth lens with positive optical power, and a ninth lens with negative optical power; the fourth and fifth lenses form a first cemented lens group, and the sixth and seventh lenses form a second cemented lens group. The full field of view of the lens satisfies the following relationship: 45°<2θ<65° Where 2θ represents the full field of view of the lens; The total length of the lens and the image plane size of the lens satisfy the following relationship: 2 <T / h<3.5 Where T represents the total length of the lens, and h represents the image plane size of the lens; The incident angle of the principal ray of the lens satisfies the following relationship: 20 <CRA<26 CRA represents the angle of incidence of the principal ray from the lens; The optical back focal length of the lens and the total length of the lens satisfy the following relationship: 0.12 <BFL / T<0.3 Where BFL represents the optical back focal length of the lens, and T represents the total length of the lens.

2. The low-distortion mapping lens according to claim 1, characterized in that, The material of any one or more of the first lens to the ninth lens includes spherical glass.

3. The low-distortion mapping lens according to claim 1, characterized in that, The refractive index and Abbe number of the first lens satisfy the following relationship: 1.45<N1<1.6 63<V1<65 Where N1 represents the refractive index of the first lens and V1 represents the Abbe number of the first lens.

4. The low-distortion mapping lens according to claim 1, characterized in that, The refractive index of the third lens satisfies the following relationship: 1.8<N3<2.1 Where N3 represents the refractive index of the third lens.

5. The low-distortion mapping lens according to claim 1, characterized in that, The refractive index of the eighth lens satisfies the following relationship: 1.85<N8<2.05 N8 represents the refractive index of the eighth lens.

6. The low-distortion mapping lens according to claim 1, characterized in that, The focal length of the lens satisfies the following relationship: 35<f<45 Where f represents the focal length of the lens.

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