Optical lens

Abstract

The utility model discloses an optical lens, which comprises a lens group and flexible sheets, and sequentially comprises a diaphragm, a first lens, a second lens and a third lens from an object side to an image side, and the flexible sheets are arranged between the first lens and the second lens and between the second lens and the third lens; the distance between the first lens and the second lens is d1, the distance between the second lens and the third lens is d2, and the following relational expressions are satisfied: 0.1 lt; d1lt; 2 mm; 0.1 lt; d2lt; d2lt; 2 mm. According to the utility model, the flexible sheet is not easy to deform, the distance between the lenses can be better maintained, so that the optical performance is optimized, the lenses are not scratched in the assembling and core adjusting processes, and the problems of poor appearance and function damage are avoided. Besides, the adjustable range of the d1 and the d2 is relatively large, so that the distance between the lenses can be flexibly adjusted according to specific requirements, a better achromatic effect is achieved, and the assembly process is simplified at the same time.

Description

Technical Field

[0001] The utility model relates to the technical field of telescope lenses, in particular to an optical lens. Background Art

[0002] Large-aperture telescopes are usually composed of 2 to 3 optical lenses, and achromatism is one of the key design goals. Traditional achromatism designs often rely on lens bonding technology, that is, bonding lenses of different materials together to offset the dispersion effect. However, there are many disadvantages of bonding lenses with too large an aperture. In order to solve the above problems, the separated achromatism design has gradually attracted attention. This design keeps the lenses separated, and in large-aperture telescopes, the way to maintain a stable air gap between lenses is usually to set a metal spacer. Since the metal spacer is only a few millimeters thick, its thin-walled structure is prone to deformation, especially under the pressure during assembly and core adjustment. More importantly, the metal spacer may scratch the surface of the lens during rotation and adjustment, causing irreversible damage to the appearance and function. In addition, the metal spacer is produced by mechanical processing, and it is difficult to ensure the consistency of each batch, which further increases the difficulty of assembly and reduces the overall production efficiency. Utility Model Content

[0003] The technical problem to be solved by the utility model is that the existing method of maintaining a stable air gap between lenses usually adopts the method of setting a metal spacer, which easily causes the metal spacer to deform and may scratch the surface of the lens during rotation adjustment.

[0004] In order to solve the above technical problems, the utility model provides an optical lens, including a lens group and a flexible sheet, which includes an aperture, a first lens, a second lens and a third lens in order from the object side to the image side, and the flexible sheet is arranged between the first lens and the second lens, and between the second lens and the third lens;

[0005] The distance between the first lens and the second lens is d1, the distance between the second lens and the third lens is d2, and the following relationship is satisfied:

[0006] 0.1 <d1<2mm;

[0007] 0.1 <d2<2mm。

[0008] Furthermore, the first lens has negative optical power, the second lens has positive optical power, and the third lens has negative optical power.

[0009] Further, the focal length of the first lens is f1, the refractive index of the first lens is N1, the Abbe number of the first lens is V1, and the following relationship is satisfied:

[0010] -350 <f1<-300mm;

[0011] 1.55 <N1<1.70;

[0012] 45 <V1<70。

[0013] Furthermore, the thickness of the first lens is T1, and satisfies the following relationship:

[0014] 3.5 <T1<8.5mm。

[0015] Further, the focal length of the second lens is f2, the refractive index of the second lens is N2, the Abbe number of the second lens is V2, and the following relationship is satisfied:

[0016] 100 <f2<130mm;

[0017] 1.40 <N2<1.65;

[0018] 75 <V2<95。

[0019] Furthermore, the thickness of the second lens is T2, and satisfies the following relationship:

[0020] 12 <T2<22mm。

[0021] Furthermore, the focal length of the third lens is f3, the refractive index of the third lens is N3, the Abbe number of the third lens is V3, and the following relationship is satisfied:

[0022] -500 <f3<-400mm;

[0023] 1.45 <N3<1.65;

[0024] 55 <V3<70。

[0025] Furthermore, the thickness of the third lens is T3, and satisfies the following relationship:

[0026] 6.5 <T3<9.0mm。

[0027] Furthermore, the distance between the aperture and the first lens is d3, and satisfies the following relationship:

[0028] d3=0.0mm.

[0029] Furthermore, the distance between the third lens and the imaging plane is d4, and satisfies the following relationship:

[0030] 300 <d4<320mm。

[0031] Compared with the prior art, the optical lens of the embodiment of the utility model has the following beneficial effects:

[0032] Compared with traditional metal spacers, the flexible sheets in the embodiments of the utility model are less likely to deform and can better maintain the distance between lenses, thereby optimizing optical performance. And due to the material characteristics of the flexible sheets, they will not scratch the lenses during assembly and core adjustment, thereby avoiding the problems of poor appearance and impaired function. In addition, since the adjustable range of d1 and d2 is large, the distance between lenses can be flexibly adjusted according to specific needs to achieve a better achromatic effect, while simplifying the assembly process and reducing the dependence on high-precision metal spacers. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a structural principle diagram of the optical lens provided by the embodiment of the utility model;

[0034] Figure 2 The utility model embodiment provides Figure 1 A partial enlarged view of the circled portion A;

[0035] Figure 3 The utility model embodiment provides Figure 1 A partial enlarged view of the circled portion B;

[0036] Figure 4 is an imaging quality point diagram of the optical lens provided by the embodiment of the utility model;

[0037] Figure 5 It is an optical distortion & field curvature diagram of the optical lens provided by the embodiment of the utility model;

[0038] Figure 6 is an axial chromatic aberration diagram of the optical lens provided by the embodiment of the utility model;

[0039] Figure 7 It is the focus shift curve of different color wavelengths of the optical lens provided by the embodiment of the utility model;

[0040] Figure 8 is a visible light PSF diagram of the optical lens provided by an embodiment of the utility model;

[0041] In the figure, 1, lens group; L1, first lens; L2, second lens; L3, third lens; 2, flexible sheet. DETAILED DESCRIPTION

[0042] The following is a further detailed description of the specific implementation of the present invention in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0043] like Figures 1 to 3 As shown in Figures 1 to 3 , the present utility model provides an optical lens, which includes a lens group 1 and a flexible thin sheet 2. From the object side to the image side, it sequentially includes a diaphragm, a first lens L1, a second lens L2, and a third lens L3. Flexible thin sheets 2 are provided between the first lens L1 and the second lens L2, and between the second lens L2 and the third lens L3; the distance between the first lens L1 and the second lens L2 is d1, and the distance between the second lens L2 and the third lens L3 is d2, and the following relational expressions are satisfied: 0.1 < d1 < 2 mm, 0.1 < d2 < 2 mm, ensuring that there is sufficient air gap between the lenses to achieve achromatism, while avoiding the risk of increasing lens deformation due to excessive gap.

[0044] Based on the above structure, compared with the traditional metal spacer rings, the flexible thin sheets 2 in this embodiment are not easily deformed, can better maintain the distance between the lenses, thereby optimizing the optical performance. And due to the material characteristics of the flexible thin sheets 2, they will not scratch the lenses during the assembly and centering processes, thus avoiding the problems of poor appearance and impaired function. In addition, since the adjustable ranges of d1 and d2 are relatively large, the distance between the lenses can be flexibly adjusted according to specific requirements to achieve a better achromatic effect, while simplifying the assembly process and reducing the dependence on high-precision metal spacer rings.

[0045] It should be noted that by controlling the edge distance between the first lens L1 and the second lens L2 to make it meet the thickness of the first specification flexible thin sheet, the first specification flexible thin sheet can be obtained by stamping according to specific aperture requirements. It should not be too thick. The obtained first specification flexible thin sheet has sufficient rigidity, is relatively smooth, and has a certain thickness, which can ensure the lens separation interval and can bear the weight of the lens without deformation (such as SOMA thin sheet, tin foil thin sheet). The relatively smooth surface can ensure the rotational adjustment of the individual lenses so that the central optical axes of each lens are on the same straight line and do not scratch the optical lens, meeting the imaging quality requirements of the center point and the design requirements. Moreover, the first specification flexible thin sheets obtained by stamping have good consistency and stable output. In this embodiment, the design freedom is wide by only controlling this distance and ignoring the central air gap between the first lens L1 and the second lens L2 and the curvature changes of the first lens L1 and the second lens L2.

[0046] Similarly, the edge distance between the second lens L2 and the third lens L3 is controlled according to this principle, but the thickness of the second specification flexible thin sheet can be different to meet different design requirements. It can be understood that the second specification flexible thin sheet can be of the same specification as the first specification flexible thin sheet.

[0047] It should also be noted that in the attached drawings, S1 is a diaphragm, S2 is the object side of the first lens L1, S3 is the image side of the first lens L1, S4 is the object side of the second lens L2, S5 is the image side of the second lens L2, S6 is the object side of the third lens L3, S7 is the image side of the third lens L3, and S8 is the imaging surface.

[0048] Furthermore, the first lens L1 has a negative focal power to diverge the light entering the telescope, providing a basis for the focusing of the subsequent lens group 1. The second lens L2 has a positive focal power and can converge parallel light beams to a point. The third lens L3 has a negative focal power and can diverge light to correct the aberrations that may be generated by the first two lenses, especially chromatic aberration and spherical aberration.

[0049] In this embodiment, the focal power distribution form of "-", "+", "-" is adopted to ensure that the second lens L2 is in the middle position and is not scratched or contaminated. It should be noted that the first lens L1 in this embodiment uses lanthanum series glass with high transmittance to improve the transmission effect of the system and make the field of view brighter. The second lens L2 uses an ultra-low dispersion material to correct axial chromatic aberration. The material has relatively soft characteristics and is easy to be scratched. Placing it in the middle is beneficial to reducing the surface defect degree of the system. The third lens L3 uses low-cost K9 glass to achieve a better imaging effect.

[0050] Furthermore, the focal length of the first lens L1 is f1, the refractive index of the first lens L1 is N1, and the Abbe number of the first lens L1 is V1, and the following relational expressions are satisfied: -350 < f1 < -300 mm to ensure the gentle divergence of light and contribute to the balance of the entire optical system; 1.55 < N1 < 1.70 to ensure that the first lens L1 can effectively bend light and avoid aberrations caused by excessive refraction; 45 < V1 < 70 to make it have a better function of reducing chromatic aberration and is beneficial to achieving high-quality imaging.

[0051] Through the above parameter design in this embodiment, it is helpful to reduce chromatic aberration, ensure that light rays of different wavelengths are focused at similar positions, and improve image clarity and color accuracy.

[0052] Furthermore, the thickness of the first lens L1 is T1, and the following relational expression is satisfied: 3.5 < T1 < 8.5 mm to ensure that the lens is strong enough to withstand the pressure during assembly and use, while maintaining appropriate light weight, avoiding that an overly thin lens may be easily damaged or deformed during installation or use, and an overly thick lens may cause an increase in weight, affecting the balance and operation convenience of the overall system.

[0053] In addition, a lens that is too thick may cause additional spherical aberration and chromatic aberration, while a lens that is too thin may not be able to adequately correct these aberrations. Through the above thickness design, the optical performance of the lens is optimized, aberrations are reduced, and image clarity and contrast are improved.

[0054] Further, the focal length of the second lens L2 is f2, the refractive index of the second lens L2 is N2, and the Abbe number of the second lens L2 is V2, and the following relational expressions are satisfied: 100 < f2 < 130 mm to effectively converge light rays; 1.40 < N2 < 1.65 to have good light transmittance and appropriate refractive power, which helps to achieve a clear image; 75 < V2 < 95 to have low dispersion, which helps to reduce chromatic aberration and improve imaging quality.

[0055] Further, the thickness of the second lens L2 is T2, and the following relational expression is satisfied: 12 < T2 < 22 mm, which helps to ensure the structural strength of the lens. In addition, it avoids an overly thick lens from increasing internal reflection and scattering, resulting in light flux loss and a decrease in imaging quality.

[0056] Further, the focal length of the third lens L3 is f3, the refractive index of the third lens L3 is N3, and the Abbe number of the third lens L3 is V3, and the following relational expressions are satisfied: -500 < f3 < -400 mm to ensure that the lens can effectively diverge light rays, and at the same time cooperate with the first two lenses to achieve the balance and performance optimization of the entire optical system; 1.45 < N3 < 1.65 to be able to effectively change the light path while maintaining appropriate refractive power and avoiding aberrations caused by excessive refraction; 55 < V3 < 70 to help reduce chromatic aberration, ensure that light rays of different wavelengths are focused near the same plane, and improve imaging quality.

[0057] Further, the thickness of the third lens L3 is T3, and the following relational expression is satisfied: 6.5 < T3 < 9.0 mm to ensure that the third lens L3 can maintain sufficient rigidity to resist mechanical stresses that may be encountered during manufacturing, assembly, and use, preventing deformation or breakage. In addition, an appropriate thickness helps to reduce the scattering and internal reflection of marginal light beams, thereby reducing aberrations such as coma and field curvature, while maintaining good light flux to ensure image clarity and brightness.

[0058] Further, the distance between the aperture stop and the first lens L1 is d3, and the following relational expression is satisfied: d3 = 0.0 mm. In this embodiment, placing the aperture stop adjacent to the first lens L1 can simplify the optical path design and reduce the propagation path length of light rays in the system, which helps to reduce the design complexity and cost of the entire optical lens. In addition, placing the aperture stop at the forefront can reduce multiple reflections and refractions of light rays inside the system, thereby reducing aberrations.

[0059] Further, the distance between the third lens L3 and the imaging surface is d4, and it satisfies the following relational expression: 300 < d4 < 320 mm, so as to optimize aberration correction while maintaining the compactness of the system, and avoid the increase in aberrations such as spherical aberration and coma that may be caused by too short a distance. An overly long distance may increase the volume and weight of the system and affect the flexibility of the optical path design at the same time.

[0060] The total optical power φ of the above optical lens system is 0.003; the product of the optical aperture and the total optical power of the system is 0.21; the total length (that is, the system length from S1 to S8) is 370 mm; the DFOV is 1.5°; the diameter of the imaging circle is D8.84 mm.

[0061] Combined Figures 4 to 8 as shown Figure 4 is the spot diagram of the imaging quality of the optical lens. The central spot diagram of its imaging quality is within the Airy Radius range, and it has excellent on-axis imaging quality.

[0062] Figure 5 is the optical distortion & field curvature diagram of the optical lens. The resulting field curvature is less than 0.5 mm. At the focal length of this system, the image field is flat, which can meet the CCD shooting requirements.

[0063] Figure 6 is the axial chromatic aberration diagram of the optical lens. In the bandwidth range of 435 nm - 656 nm of the on-axis field of view, the chromatic aberrations at 0.95 aperture basically coincide, and good correction is obtained.

[0064] Figure 7 is the focus shift curve of different color wavelengths of the optical lens. In the bandwidth range of 486 nm, 546 nm, and 656 nm of the on-axis field of view, the focus shifts of different color wavelengths at 0.95 aperture basically coincide, representing the apochromatism of the system.

[0065] The visible light wavelength values are approximately 486 nm, 546 nm, and 656 nm. A telescopic optical system generally needs to correct chromatic aberration, that is, the focus shifts of the 486 nm and 656 nm wavelengths at the maximum aperture or above 0.707 aperture should basically coincide so as not to appear multi-color colored circles. For 546 nm, it is generally not corrected. However, apochromatism requires that the focus shifts of 486 nm, 546 nm, and 656 nm at the maximum aperture or above 0.707 aperture should basically coincide to be called apochromatism. Generally, optical glass materials with ultra-low dispersion (corresponding to a very large Vd value) are required. That is, the second lens L2 of this optical lens plays an important role in the apochromatism of this optical lens.

[0066] Figure 8This is the visible light complex color PSF diagram of the optical lens. It can be seen that the Strehl value of the center point is greater than 0.68. Under the conditions of this optical lens and a certain NA value, it has a higher resolution.

[0067] In summary, the embodiment of the utility model provides an optical lens, whose flexible thin sheet 2 is less likely to deform than the traditional metal spacer, and can better maintain the distance between lenses, thereby optimizing the optical performance. And due to the material characteristics of the flexible thin sheet 2, they will not scratch the lens during the assembly and core adjustment process, thereby avoiding the problems of poor appearance and impaired function. In addition, since the adjustable range of d1 and d2 is large, the distance between lenses can be flexibly adjusted according to specific needs to achieve a better achromatic effect, while simplifying the assembly process, achieving core adjustment, improving product yield, and reducing dependence on high-precision metal spacers.

[0068] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and substitutions can be made without departing from the technical principle of the present invention. These improvements and substitutions should also be regarded as the protection scope of the present invention.

Claims

1. An optical lens, characterized in that: The lens group includes a lens group and a flexible sheet, which includes an aperture, a first lens, a second lens and a third lens in order from the object side to the image side, and the flexible sheet is disposed between the first lens and the second lens, and between the second lens and the third lens; The distance between the first lens and the second lens is d1, the distance between the second lens and the third lens is d2, and the following relationship is satisfied: 0.1 <d1<2mm; 0.1 <d2<2mm。 2. The optical lens according to claim 1, characterized in that: The first lens has negative optical power, the second lens has positive optical power, and the third lens has negative optical power.

3. The optical lens according to claim 1, characterized in that: The focal length of the first lens is f1, the refractive index of the first lens is N1, the Abbe number of the first lens is V1, and the following relationship is satisfied: -350 <f1<-300mm; 1.55<N1<1.70； 45<V1<70。 4. The optical lens according to claim 1, characterized in that: The thickness of the first lens is T1, and satisfies the following relationship: 3.5 <T1<8.5mm。 5. The optical lens according to claim 1, characterized in that: The focal length of the second lens is f2, the refractive index of the second lens is N2, the Abbe number of the second lens is V2, and the following relationship is satisfied: 100 <f2<130mm; 1.40<N2<1.65； 75<V2<95。 6. The optical lens according to claim 1, characterized in that: The thickness of the second lens is T2, and satisfies the following relationship: 12 <T2<22mm。 7. The optical lens according to claim 1, characterized in that: The focal length of the third lens is f3, the refractive index of the third lens is N3, the Abbe number of the third lens is V3, and the following relationship is satisfied: -500 <f3<-400mm; 1.45<N3<1.65； 55<V3<70。 8. The optical lens according to claim 1, characterized in that: The thickness of the third lens is T3, and satisfies the following relationship: 6.5 <T3<9.0mm。 9. The optical lens according to claim 1, characterized in that: The distance between the aperture and the first lens is d3, and satisfies the following relationship: d3=0.0mm.

10. The optical lens according to claim 1, characterized in that: The distance between the third lens and the imaging plane is d4, and satisfies the following relationship: 300 <d4<320mm。

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