A telephoto lens

Abstract

An embodiment of the present invention provides a telephoto lens, which includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens and an eighth lens arranged in sequence from the object side to the image side along the optical axis; the first lens, the fourth lens, the sixth lens and the seventh lens all have positive optical powers, and the second lens, the third lens, the fifth lens and the eighth lens all have negative optical powers. An embodiment of the present invention provides a telephoto lens to provide a telephoto lens with a large target surface and a small volume.

Description

Technical Field

[0001] The present invention relates to the technology of optical lenses, and particularly to a telephoto lens. Background Art

[0002] With the rapid development of technology and economy, the society has higher and higher requirements for optical imaging lenses. For example, while ensuring the ability to capture and observe objects at a long distance, it is also required that the imaging chip be larger and the lens volume be smaller; however, the existing optical lenses are difficult to meet the increasing demands. Summary of the Invention

[0003] Embodiments of the present invention provide a telephoto lens to provide a telephoto lens with a large target surface and a small volume.

[0004] Embodiments of the present invention provide a telephoto lens, including a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, and an eighth lens arranged in sequence from the object side to the image side along the optical axis;

[0005] The first lens, the fourth lens, the sixth lens, and the seventh lens all have positive optical powers, and the second lens, the third lens, the fifth lens, and the eighth lens all have negative optical powers.

[0006] Optionally, the optical power of the first lens is φ1, the optical power of the second lens is φ2, the optical power of the third lens is φ3, the optical power of the fourth lens is φ4, the optical power of the fifth lens is φ5, the optical power of the sixth lens is φ6, the optical power of the seventh lens is φ7, the optical power of the eighth lens is φ8, and the optical power of the telephoto lens is φ, satisfying:

[0007] 0.50 ≤ |φ1 / φ| ≤ 0.60;

[0008] 0.35 ≤ |φ2 / φ| ≤ 0.60;

[0009] 0.55 ≤ |φ3 / φ| ≤ 0.95;

[0010] 0.50 ≤ |φ4 / φ| ≤ 1.30;

[0011] 0.50 ≤ |φ5 / φ| ≤ 1.30;

[0012] 0.60 ≤ |φ6 / φ| ≤ 1.5;

[0013] 0.30 ≤ |φ7 / φ| ≤ 0.8;

[0014] 0.25 ≤ |φ8 / φ| ≤ 0.55.

[0015] Optionally, the third lens and the fourth lens are adhesively bonded to form a doublet lens group with a positive optical power.

[0016] Optionally, the optical power of the doublet lens group formed by adhesively bonding the third lens and the fourth lens is φ9, and the optical power of the telephoto lens is φ, satisfying:

[0017] 0.25 ≤ |φ9 / φ| ≤ 0.55.

[0018] Optionally, the fifth lens and the sixth lens are adhesively bonded to form a doublet lens group with a positive optical power.

[0019] Optionally, the optical power of the doublet lens group formed by adhesively bonding the fifth lens and the sixth lens is φ10, and the optical power of the telephoto lens is φ, satisfying:

[0020] 0.25 ≤ |φ10 / φ| ≤ 0.55.

[0021] Optionally, the air gap between the fourth lens and the fifth lens on the optical axis is T45, the air gap between the sixth lens and the seventh lens on the optical axis is T67, the central thickness of the seventh lens is CT7, and the overall optical length of the telephoto lens is TTL, satisfying:

[0022] 0.002 ≤ T45 / TTL ≤ 0.1;

[0023] 0.002 ≤ T67 / TTL ≤ 0.1;

[0024] 0.02 ≤ CT7 / TTL ≤ 0.1.

[0025] Optionally, the Abbe number of the fifth lens is VD5, and the Abbe number of the sixth lens is VD6, satisfying:

[0026] 25 ≤ |VD5 - VD6| ≤ 65.

[0027] Optionally, the refractive index of the eighth lens is ND8, satisfying:

[0028] 1.55 ≤ ND8 ≤ 1.85.

[0029] Optionally, the focal length of the telephoto lens is EFL, and the overall optical length of the telephoto lens is TTL, satisfying:

[0030] 0.4 ≤ EFL / TTL ≤ 0.65.

[0031] In the long - focal - length lens of Embodiment 1 of the present invention, the optical powers of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens and the eighth lens are positive, negative, negative, positive, negative, positive, positive and negative respectively. Thus, a long - focal - length lens with a large image - plane size and a small volume is provided. This long - focal - length lens has good imaging performance, the overall optical length satisfies TTL≤40mm, and it can be used with a maximum 1 / 1.7” chip at most. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic structural diagram of the long - focal - length lens in Embodiment 1 of the present invention;

[0033] Figure 2 It is a spherical aberration curve graph of the long - focal - length lens in Embodiment 1 of the present invention;

[0034] Figure 3 It is a ray fan diagram of the long - focal - length lens in Embodiment 1 of the present invention;

[0035] Figure 4 It is a field curvature curve graph of the long - focal - length lens in Embodiment 1 of the present invention;

[0036] Figure 5 It is a distortion curve graph of the long - focal - length lens in Embodiment 1 of the present invention;

[0037] Figure 6 It is a spot diagram of the long - focal - length lens in Embodiment 1 of the present invention;

[0038] Figure 7 It is a schematic structural diagram of the long - focal - length lens in Embodiment 2 of the present invention;

[0039] Figure 8 It is a spherical aberration curve graph of the long - focal - length lens in Embodiment 2 of the present invention;

[0040] Figure 9 It is a ray fan diagram of the long - focal - length lens in Embodiment 2 of the present invention;

[0041] Figure 10 It is a field curvature curve graph of the long - focal - length lens in Embodiment 2 of the present invention;

[0042] Figure 11 It is a distortion curve graph of the long - focal - length lens in Embodiment 2 of the present invention;

[0043] Figure 12 It is a spot diagram of the long - focal - length lens in Embodiment 2 of the present invention;

[0044] Figure 13 It is a schematic structural diagram of the long - focal - length lens in Embodiment 3 of the present invention;

[0045] Figure 14 It is a spherical aberration curve graph of the long - focal - length lens in Embodiment 3 of the present invention;

[0046] Figure 15 It is the light fan diagram of the telephoto lens in Embodiment 3 of the present invention;

[0047] Figure 16 It is the field curvature curve diagram of the telephoto lens in Embodiment 3 of the present invention;

[0048] Figure 17 It is the distortion curve diagram of the telephoto lens in Embodiment 3 of the present invention;

[0049] Figure 18 It is the spot diagram of the telephoto lens in Embodiment 3 of the present invention. Detailed implementation manners

[0050] The present invention will be further described in detail below with reference to the drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the present invention, rather than limiting the present invention. Additionally, it should be noted that for the convenience of description, only the parts related to the present invention rather than all the structures are shown in the drawings.

[0051] Embodiment 1

[0052] Figure 1 It is the structural schematic diagram of the telephoto lens in Embodiment 1 of the present invention. Referring to Figure 1 , the telephoto lens includes a first lens 1, a second lens 2, a third lens 3, a fourth lens 4, a fifth lens 5, a sixth lens 6, a seventh lens 7, and an eighth lens 8 arranged in sequence from the object side to the image side along the optical axis. The first lens 1, the fourth lens 4, the sixth lens 6, and the seventh lens 7 all have positive optical powers, and the second lens 2, the third lens 3, the fifth lens 5, and the eighth lens 8 all have negative optical powers.

[0053] For the telephoto lens in Embodiment 1 of the present invention, the optical powers of the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, the sixth lens 6, the seventh lens 7, and the eighth lens 8 are positive, negative, negative, positive, negative, positive, positive, and negative respectively. Thus, a telephoto lens with a large target surface and a small volume is provided. This telephoto lens has good imaging performance, the overall optical length satisfies TTL ≤ 40 mm, and it can be used with a maximum chip of 1 / 1.7".

[0054] Exemplarily, the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, the sixth lens 6, the seventh lens 7, and the eighth lens 8 are all glass spherical lenses.

[0055] Optionally, the optical power of the first lens 1 is φ1, the optical power of the second lens 2 is φ2, the optical power of the third lens 3 is φ3, the optical power of the fourth lens 4 is φ4, the optical power of the fifth lens 5 is φ5, the optical power of the sixth lens 6 is φ6, the optical power of the seventh lens 7 is φ7, the optical power of the eighth lens 8 is φ8, and the optical power of the telephoto lens is φ. It satisfies: 0.50 ≤ |φ1 / φ| ≤ 0.60, 0.35 ≤ |φ2 / φ| ≤ 0.60, 0.55 ≤ |φ3 / φ| ≤ 0.95, 0.50 ≤ |φ4 / φ| ≤ 1.30, 0.50 ≤

[0056] |φ5 / φ| ≤ 1.30, 0.60 ≤ |φ6 / φ| ≤ 1.5, 0.30 ≤ |φ7 / φ| ≤ 0.8, 0.25 ≤ |φ8 / φ| ≤ 0.55. The eighth lens 8 is a glass spherical lens with negative optical power and is located close to the image plane, which can effectively correct aberrations such as field curvature. In the embodiment of the present invention, through the reasonable distribution of the optical powers of each lens, the light rays reach the imaging plane smoothly. While reducing aberrations and improving imaging quality, the assembly tolerance is reduced and the production yield is increased.

[0057] Optionally, the third lens 3 and the fourth lens 4 are bonded into a doublet lens group with positive optical power. In the embodiment of the present invention, the third lens 3 is a glass spherical lens with negative optical power, the fourth lens 4 is a glass spherical lens with positive optical power, and the third lens 3 and the fourth lens 4 are bonded into a doublet lens group with positive optical power. The cemented lenses can be spaced by compressed air, reducing the volume while reducing the assembly tolerance and increasing the yield, and reducing the production cost.

[0058] Optionally, the optical power of the doublet lens group formed by bonding the third lens 3 and the fourth lens 4 is φ9, and the optical power of the telephoto lens is φ, satisfying: 0.25 ≤ |φ9 / φ| ≤ 0.55.

[0059] Optionally, the fifth lens 5 and the sixth lens 6 are bonded into a doublet lens group with positive optical power. In the embodiment of the present invention, the fifth lens 5 is a glass spherical lens with negative optical power, the sixth lens 6 is a glass spherical lens with positive optical power, and the fifth lens 5 and the sixth lens 6 are bonded into a doublet lens group with positive optical power. The combination of the fifth lens 5 and the sixth lens 6 using materials with different dispersion coefficients can make the dispersions compensate each other to achieve the purpose of achromatism, which is beneficial to improving the imaging performance of the telephoto lens.

[0060] Optionally, the optical power of the doublet lens group formed by bonding the fifth lens 5 and the sixth lens 6 is φ10, and the optical power of the telephoto lens is φ, satisfying: 0.25 ≤ |φ10 / φ| ≤ 0.55.

[0061] Optionally, the air gap between the fourth lens 4 and the fifth lens 5 on the optical axis is T45, the air gap between the sixth lens 6 and the seventh lens 7 on the optical axis is T67, the central thickness of the seventh lens 7 is CT7, and the overall optical length of the telephoto lens is TTL, satisfying: 0.002 ≤ T45 / TTL ≤ 0.1, 0.002 ≤ T67 / TTL ≤ 0.1, 0.02 ≤ CT7 / TTL ≤ 0.1. In the embodiment of the present invention, by controlling the lens thickness and the air gap between the lenses on the optical axis, the overall structure can be made compact, effectively compressing the overall optical length and reducing the volume of the telephoto lens.

[0062] Optionally, the Abbe number of the fifth lens 5 is VD5, and the Abbe number of the sixth lens 6 is VD6, satisfying: 25 ≤ ∣VD5 - VD6∣ ≤ 65. When the Abbe numbers of the fifth lens 5 and the sixth lens 6 satisfy the condition 25 ≤

[0063] ∣VD5 - VD6∣ ≤ 65, chromatic dispersion can be compensated for each other, which is beneficial to the correction of the overall chromatic aberration of the telephoto lens.

[0064] Optionally, the refractive index of the eighth lens 8 is ND8, satisfying: 1.55 ≤ ND8 ≤ 1.85. In the embodiment of the present invention, the eighth lens 8 uses a material with a relatively high refractive index. By reasonably selecting the material, the deflection angle of the light exiting can be increased, thereby increasing the image height to ensure a sufficient target surface.

[0065] Optionally, the focal length of the telephoto lens is EFL, and the overall optical length of the telephoto lens is TTL, satisfying: 0.4 ≤ EFL / TTL ≤ 0.65. In the embodiment of the present invention, by controlling the ratio of the focal length to the overall length, it is possible to ensure that the overall length is shortened while the focal length remains unchanged, which is beneficial to reducing the volume of the telephoto lens while ensuring the optical performance.

[0066] Exemplarily, referring to Figure 1 , the telephoto lens further includes a diaphragm STO, and the diaphragm STO is located between the second lens 2 and the third lens 3. The telephoto lens further includes a filter 9, and the filter 9 is located on the side of the eighth lens 8 away from the seventh lens 7.

[0067] Table 1 shows a set of design values of the telephoto lens in Embodiment 1

[0068] Surface Serial Number Surface Type Radius of Curvature (mm) Thickness (mm) Refractive Index Abbe Number Semi-Diameter (mm) S1 Standard Surface 18.2227 1.9467 1.68 94.0 6.7741 S2 Standard Surface 60.9381 1.0320 6.4857 S3 Standard Surface -37.2826 0.4830 1.61 64.2 6.4308 S4 Standard Surface 188.0557 0.1368 6.2277 STO Standard Surface PL 12.5327 6.2189 S6 Standard Surface 59.7927 0.7923 1.56 94.0 5.7733 S7 Standard Surface 12.2421 3.2707 1.43 55.4 5.6944 S8 Standard Surface -24.5099 0.1407 5.6957 S9 Standard Surface 61.9318 0.8199 1.66 5.6030 S10 Standard Surface 10.2506 2.6886 1.55 30.0 5.4653 S11 Standard Surface -217.9666 0.1506 94.0 5.4378 S12 Standard Surface 11.8045 2.8034 1.68 5.3559 S13 Standard Surface 22.8616 0.0250 42.5 4.8835 S14 Standard Surface 11.1876 4.9182 1.56 4.8356 S15 Standard Surface 6.5511 7.0096 30.0 3.9037 S16 Standard Surface PL 0.7000 1.52 64.2 4.5928 S17 Standard Surface PL 0.5562 4.6496 IMA Standard Surface 4.7188

[0069] Table 1 shows a set of design values of the telephoto lens in Embodiment 1. The specific numerical values can be adjusted according to product requirements and are not a limitation to the embodiments of the present invention. The telephoto lens shown in Table 1 can be Figure 1As shown. A lens generally includes two surfaces, and each surface is a refractive surface. The surface numbers in Table 1 are numbered according to the surfaces of each lens. Among them, the surface number "S1" represents the front surface (i.e., the object side surface) of the first lens 1, and the surface number "S2" represents the rear surface (i.e., the image side surface) of the first lens 1, and so on, which will not be elaborated here. It should be noted that "STO" in the "Surface Number" column represents the plane where the stop STO is located. "IMA" in the "Surface Number" column represents the image plane. The radius of curvature represents the degree of curvature of the lens surface. A positive radius of curvature value indicates that the center of curvature is on the side of the surface close to the image side, and a negative radius of curvature value represents that the center of curvature is on the side of the surface far from the image side. "PL" in the "Radius of Curvature" column represents that the surface is a plane. The value in the "Thickness" column represents the axial distance from the current surface to the next surface. The "Refractive Index" column represents the refractive index of the medium between the current surface and the next surface. The space in the "Refractive Index" column is the refractive index of air, and the refractive index of air is 1. The value in the "Semi-Diameter" column represents half of the aperture size of the current surface. The Abbe number represents the dispersion characteristic of the material between the current surface and the next surface to light, and the space represents that the current position is air.

[0070] In Embodiment 1, the focal length of the telephoto lens is 21.5 mm, and the field of view angle FOV = 25°.

[0071] Figure 2 This is the spherical aberration curve graph of the telephoto lens in Embodiment 1 of the present invention. Refer to Figure 2 , the vertical direction represents the normalization of the aperture, 0 represents on the optical axis, and the vertex in the vertical direction represents the maximum pupil radius. The horizontal direction represents the offset relative to the ideal focus, with the unit of millimeter (mm). Figure 2 The different linear curves in Figure 2 represent different wavelengths of the system imaging. It can be seen from

[0072] Figure 3 that the axial aberrations of different wavelengths are all controlled within the range of (-0.1 mm, +0.1 mm), indicating that the spherical aberration of the telephoto lens at each wavelength is well controlled and can meet the requirements of wide-spectrum applications. Figure 3 This is the ray fan diagram of the telephoto lens in Embodiment 1 of the present invention. The scaling ratio is 40 um.

[0073] Figure 4 This is the field curvature curve graph of the telephoto lens in Embodiment 1 of the present invention. Refer to Figure 4 , Figure 4The horizontal coordinate represents the magnitude of field curvature, with the unit of mm. The vertical coordinate represents the normalized image height, without unit. Among them, T represents meridian, and S represents sagittal. From Figure 4 it can be seen that for the lens provided in this embodiment, from the light with a wavelength of 436 nm to the light with a wavelength of 656 nm, the field curvature is effectively controlled, that is, when imaging, the image quality difference between the center and the periphery is small.

[0074] Figure 5 This is the distortion curve graph of the telephoto lens in the first embodiment of the present invention. Refer to Figure 5 , the horizontal coordinate represents the magnitude of distortion, with the unit of %. The vertical coordinate represents the normalized image height, without unit. From Figure 5 it can be seen that the distortion of the telephoto lens provided in this embodiment is well corrected, and the imaging distortion is less than 1.3%.

[0075] Figure 6 This is the spot diagram of the telephoto lens in the first embodiment of the present invention. Refer to Figure 6 , Figure 6 which shows the spot sizes of each waveband in different fields of view. Among them, the maximum RMS radius is 5.33 um, indicating that the system has small aberrations and good imaging quality, and can meet the requirements of wide-spectrum applications.

[0076] Embodiment 2

[0077] The same parts as those in Embodiment 1 will not be described in detail here.

[0078] Table 2 shows a set of design values of the telephoto lens in Embodiment 2

[0079]

[0080]

[0081] Table 2 shows a set of design values of the telephoto lens in Embodiment 2. The specific numerical values can be adjusted according to product requirements, and it is not a limitation to the embodiments of the present invention. The telephoto lens shown in Table 2 can be Figure 7 as shown in

[0082] In Embodiment 2, the focal length of the telephoto lens is 21.4 mm, and the field of view angle FOV = 26°.

[0083] Figure 12 This is the spot diagram of the telephoto lens in the second embodiment of the present invention. Refer to Figure 12 , Figure 12 which shows the spot sizes of each waveband in different fields of view. Among them, the maximum RMS radius is 3.95 um, indicating that the system has small aberrations and good imaging quality, and can meet the requirements of wide-spectrum applications.

[0084] Embodiment 3

[0085] Details that are the same as those in the first embodiment will not be described herein again.

[0086] Table 3 shows a set of design values of the telephoto lens in the third embodiment

[0087]

[0088]

[0089] Table 3 shows a set of design values of the telephoto lens in the third embodiment. The specific numerical values can be adjusted according to product requirements, and it is not a limitation to the embodiments of the present invention. The telephoto lens shown in Table 3 can be Figure 13 as shown in

[0090] In the third embodiment, the focal length of the telephoto lens is 21.5 mm, and the field of view FOV = 25°.

[0091] Figure 18 This is the spot diagram of the telephoto lens in the third embodiment of the present invention. Refer to Figure 18 , Figure 18 which shows the spot sizes of each band at different fields of view. The maximum RMS radius is 4.68 um, indicating that the aberrations of the system are small and it has good imaging quality, which can meet the requirements of wide-spectrum applications.

[0092] Note that the above is only the preferred embodiment of the present invention and the technical principles applied. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein. Various obvious changes, re-adjustments, combinations with each other, and substitutions can be made by those skilled in the art without departing from the protection scope of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments. Without departing from the concept of the present invention, more other equivalent embodiments can be included, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A telephoto lens, characterized in that, It includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, and an eighth lens arranged in sequence from the object side to the image side along the optical axis; The first lens, the fourth lens, the sixth lens, and the seventh lens all have positive optical powers, and the second lens, the third lens, the fifth lens, and the eighth lens all have negative optical powers; The optical power of the first lens is φ1, the optical power of the second lens is φ2, the optical power of the third lens is φ3, the optical power of the fourth lens is φ4, the optical power of the fifth lens is φ5, the optical power of the sixth lens is φ6, the optical power of the seventh lens is φ7, the optical power of the eighth lens is φ8, and the optical power of the telephoto lens is φ, satisfying: 0.50 ≤ |φ1 / φ| ≤ 0.60; 0.35 ≤ |φ2 / φ| ≤ 0.60; 0.55 ≤ |φ3 / φ| ≤ 0.95; 0.50 ≤ |φ4 / φ| ≤ 1.30; 0.50 ≤ |φ5 / φ| ≤ 1.30; 0.60 ≤ |φ6 / φ| ≤ 1.5; 0.30 ≤ |φ7 / φ| ≤ 0.8; 0.25 ≤ |φ8 / φ| ≤ 0.55; The third lens and the fourth lens are cemented into a doublet lens group with positive optical power; The fifth lens and the sixth lens are cemented into a doublet lens group with positive optical power; The air gap between the fourth lens and the fifth lens on the optical axis is T45, the air gap between the sixth lens and the seventh lens on the optical axis is T67, the central thickness of the seventh lens is CT7, and the overall optical length of the telephoto lens is TTL, satisfying: 0.002 ≤ T45 / TTL ≤ 0.1; 0.002 ≤ T67 / TTL ≤ 0.1; 0.02 ≤ CT7 / TTL ≤ 0.

1.

2. The telephoto lens according to claim 1, wherein The optical power of the doublet lens group formed by cementing the third lens and the fourth lens is φ9, satisfying: 0.25 ≤ |φ9 / φ| ≤ 0.

55.

3. The telephoto lens according to claim 1, wherein, The optical power of the doublet lens group formed by cementing the fifth lens and the sixth lens is φ10, satisfying: 0.25 ≤ |φ10 / φ| ≤ 0.

55.

4. The telephoto lens according to claim 1, wherein The Abbe number of the fifth lens is VD5, and the Abbe number of the sixth lens is VD6, satisfying: 25 ≤ |VD5 - VD6| ≤ 65.

5. The telephoto lens according to claim 1, characterized in that, The refractive index of the eighth lens is ND8, satisfying: 1.55 ≤ ND8 ≤ 1.

85.

6. The telephoto lens according to claim 1, characterized in that, The focal length of the telephoto lens is EFL, satisfying: 0.4 ≤ EFL / TTL ≤ 0.65.

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