A large-aperture medium-format wide-angle autofocus lens and an image pickup device

Abstract

The present invention provides a large-aperture medium-format wide-angle autofocus lens and an image pickup device. The lens sequentially includes, from the object side to the image side: a first lens group with positive optical power, a second lens group with negative optical power, a third lens group with negative optical power, an aperture stop, a fourth lens group with positive optical power, and a fifth lens group with negative optical power; during the focusing process, the second lens group moves along the optical axis from the object side to the image side, and the fourth lens group moves along the optical axis from the image side to the object side; the lens satisfies the following conditional expressions: 0.5 < F1 / F < 2.5; -3.5 < F2 / F < -2; 0.5 < F4 / F < 1.5; 1 < F / H < 2.5. This solution can achieve better imaging quality at a relatively large aperture, so that the medium-format lens can be adapted to large-aperture photography and videography.

Description

Technical Field

[0001] The present invention relates to the field of imaging technologies, and in particular, to a large-aperture medium-format wide-angle autofocus lens and an image pickup device. Background Art

[0002] With the development of the photography industry, users have higher and higher requirements for cameras. Even full-frame cameras cannot meet the pursuit of these high-end users for extreme photography, so they turn to medium-format cameras.

[0003] In the related art, due to the relatively large size of the sensor of medium-format cameras, there are some limitations in the lenses matching such cameras on the market. For example, although some lenses are short in length and high in resolution, their apertures are not large enough, and more exposure time is required for night shooting; or, some other lenses are small in size and have high-performance optical image quality, but their apertures are also not large enough, resulting in poor adaptability of these lenses in specific environments. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a large-aperture medium-format wide-angle autofocus lens and an image pickup device, aiming to solve the problem that medium-format lenses in the related art are difficult to adapt to large-aperture photography and imaging.

[0005] To solve the above technical problem, in a first aspect of the present invention, a large-aperture medium-format wide-angle autofocus lens is provided, which sequentially includes, from the object side to the image side: a first lens group with positive optical power, a second lens group with negative optical power, a third lens group with negative optical power, an aperture stop, a fourth lens group with positive optical power, and a fifth lens group with negative optical power;

[0006] During the focusing process, the second lens group moves along the optical axis from the object side to the image side, and the fourth lens group moves along the optical axis from the image side to the object side;

[0007] The large-aperture medium-format wide-angle autofocus lens satisfies the following conditional formulas:

[0008] 0.5 < F1 / F < 2.5;

[0009] -3.5 < F2 / F < -2;

[0010] 0.5 < F4 / F < 1.5;

[0011] 1 < F / H < 2.5;

[0012] Wherein, F1 is the combined focal length of the first lens group, F2 is the combined focal length of the second lens group, F4 is the combined focal length of the fourth lens group, F is the effective focal length of the lens at infinity working distance, and H is the semi-image height of the lens.

[0013] Optionally, at least two of the lenses of the first lens group, the second lens group, the third lens, the fourth lens group, and the fifth lens group are aspherical lenses.

[0014] Optionally, during the focusing process, the first lens group, the third lens group, and the fifth lens group are fixed lens groups.

[0015] Optionally, the first lens group sequentially includes, from the object side to the image side: a first lens with a negative optical power, a first optical element with a positive or negative optical power, and a fourth lens with a positive optical power;

[0016] Wherein, the first optical element sequentially includes, from the object side to the image side, a second lens with a negative optical power and a third lens with a positive optical power, and the second lens and the third lens are combined into a cemented lens; or,

[0017] The first optical element is a single lens.

[0018] Optionally, the second lens group includes at least one lens with a refractive index Nd≥1.8.

[0019] Optionally, the second lens group includes a second optical element with a negative optical power;

[0020] Wherein, the second optical element sequentially includes, from the object side to the image side, a fifth lens with a positive optical power and a sixth lens with a negative optical power, and the fifth lens and the sixth lens are combined into a cemented lens; or,

[0021] The second optical element is a single lens.

[0022] Optionally, the third lens group includes a third optical element with a negative optical power;

[0023] Wherein, the third optical element sequentially includes a seventh lens and an eighth lens, one of the seventh lens and the eighth lens has a positive optical power and the other has a negative optical power, and the seventh lens and the eighth lens are combined into a cemented lens; or,

[0024] The third optical element is a single lens.

[0025] Optionally, the seventh lens and the eighth lens satisfy the following conditional formula:

[0026] |Nd07 - Nd08| < 0.3;

[0027] Wherein, Nd07 is the refractive index of the seventh lens, and Nd08 is the refractive index of the eighth lens.

[0028] Optionally, the fourth lens group includes at least one lens with an Abbe number Vd≥60.

[0029] Optionally, the fourth lens group includes, in order from the object side to the image side: a ninth lens with a positive refractive power and a fourth optical element with a positive refractive power;

[0030] wherein the fourth optical element includes, in order from the object side to the image side, a tenth lens with a positive refractive power and an eleventh lens with a negative refractive power, and the tenth lens and the eleventh lens are combined into a cemented lens; or,

[0031] the fourth optical element is a single lens.

[0032] Optionally, the fourth lens group includes, in order from the object side to the image side: a fifth optical element with a positive refractive power and an eleventh lens with a positive refractive power;

[0033] wherein the fifth optical element includes, in order from the object side to the image side, a ninth lens with a negative refractive power and a tenth lens with a positive refractive power, and the ninth lens and the tenth lens are combined into a cemented lens; or,

[0034] the fifth optical element is a single lens.

[0035] Optionally, the fifth lens group includes at least one lens with a refractive index Nd≥1.8.

[0036] Optionally, the fifth lens group includes, in order from the object side to the image side: a twelfth lens with a positive refractive power, a thirteenth lens with a negative refractive power, a fourteenth lens with a negative refractive power, and a fifteenth lens with a positive refractive power;

[0037] wherein the refractive index Nd≥1.8 of at least one of the twelfth lens, the fourteenth lens, and the fifteenth lens.

[0038] Optionally, the fifth lens group includes, in order from the object side to the image side: a twelfth lens with a positive refractive power, a sixth optical element with a negative refractive power, and a fifteenth lens with a negative refractive power;

[0039] wherein the sixth optical element includes, in order from the object side to the image side, a thirteenth lens with a positive refractive power and a fourteenth lens with a negative refractive power, and the thirteenth lens and the fourteenth lens are combined into a cemented lens; or,

[0040] the sixth optical element is a single lens.

[0041] In a second aspect of the present invention, an image pickup device is provided, including an image sensor and the large-aperture medium-format wide-angle autofocus lens described in any one of the above, and the image sensor is configured to receive an optical image formed by the large-aperture medium-format wide-angle autofocus lens.

[0042] Compared with the related art, a large-aperture medium-format wide-angle autofocus lens and an image pickup device in the present invention have the beneficial effects that: by adjusting the size of the aperture stop, the aperture value of the lens is controlled, and thus large-aperture photography and videography are realized; the second lens group moves along the optical axis from the object side to the image side, and the fourth lens group moves along the optical axis from the image side to the object side, that is, the second lens group and the fourth lens group move towards each other for focusing, so that the optical system of the entire lens can achieve better imaging quality under a larger aperture, and thus the medium-format lens can be adapted to large-aperture photography and videography. Moreover, through the combination of positive, negative, negative, positive, and negative lens groups, the lens can effectively correct various aberrations, such as spherical aberration, chromatic aberration, and distortion, etc., improve the imaging quality, and ensure the clarity and sharpness of the picture while maintaining a large aperture. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the related art, the following will briefly introduce the drawings required for use in the description of the embodiments or the related art. Obviously, the following drawings are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative efforts.

[0044] Figure 1 is a schematic structural diagram of the lens provided in Embodiment 1 of the present invention;

[0045] Figure 2 is an axial chromatic aberration curve diagram of the lens provided in Embodiment 1 of the present invention when focused at infinity;

[0046] Figure 3 is a field curvature and distortion schematic diagram of the lens provided in Embodiment 1 of the present invention when focused at infinity;

[0047] Figure 4 is an axial chromatic aberration curve diagram of the lens provided in Embodiment 1 of the present invention at the closest focusing distance;

[0048] Figure 5 is a field curvature and distortion schematic diagram of the lens provided in Embodiment 1 of the present invention at the closest focusing distance;

[0049] Figure 6 is a schematic structural diagram of the lens provided in Embodiment 2 of the present invention;

[0050] Figure 7It is the axial chromatic aberration curve diagram of the lens provided in Embodiment 2 of the present invention when focused at infinity;

[0051] Figure 8 It is a schematic diagram of field curvature and distortion of the lens provided in Embodiment 2 of the present invention when focused at infinity;

[0052] Figure 9 It is the axial chromatic aberration curve diagram of the lens provided in Embodiment 2 of the present invention when focused at the nearest focusing distance;

[0053] Figure 10 It is a schematic diagram of field curvature and distortion of the lens provided in Embodiment 2 of the present invention when focused at the nearest focusing distance. Detailed implementation manners

[0054] The embodiments of the present invention will be described in detail below. Examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals indicate the same or similar elements or elements with the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to explain the present invention and should not be construed as limiting the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0055] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "circumferential", "radial", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the present invention.

[0056] In addition, the terms "first" and "second" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, "a plurality of" means two or more unless otherwise specifically defined.

[0057] Embodiment:

[0058] An embodiment of the present invention provides an image pickup device, including an image sensor and a large-aperture medium-format wide-angle autofocus lens. The image sensor is configured to receive an optical image formed by the large-aperture medium-format wide-angle autofocus lens. Specifically, the light reflected by the object passes through the large-aperture medium-format wide-angle autofocus lens and then forms an image and irradiates on the photosensitive surface of the image sensor. The photosensitive surface of the image sensor receives the optical image and converts it into an image electrical signal for output, thereby realizing functions such as photographing or video recording of the image pickup device. Among them, the image sensor can be a charge-coupled device, a complementary metal oxide semiconductor, etc. The image pickup device can be a camera. The imaging module of the camera is detachably connected to the large-aperture medium-format wide-angle autofocus lens. The imaging module is provided with an image sensor. When the imaging module is connected to the large-aperture medium-format wide-angle autofocus lens, the image sensor is located on the image side of the large-aperture medium-format wide-angle autofocus lens.

[0059] Please refer to Figure 1 and Figure 6 , the large-aperture medium-format wide-angle autofocus lens sequentially includes, from the object side to the image side: a first lens group G01 with a positive optical power, a second lens group G02 with a negative optical power, a third lens group G03 with a negative optical power, an aperture stop STO, a fourth lens group G04 with a positive optical power, and a fifth lens group G05 with a negative optical power. During the focusing process, the second lens group G02 moves along the optical axis from the object side to the image side, and the fourth lens group G04 moves along the optical axis from the image side to the object side. The large-aperture medium-format wide-angle autofocus lens satisfies the following conditional formulas:

[0060] 0.5 < F1 / F < 2.5, (1);

[0061] -3.5 < F2 / F < -2, (2);

[0062] 0.5 < F4 / F < 1.5, (3);

[0063] 1 < F / H < 2.5, (4);

[0064] Among them, F1 is the combined focal length of the first lens group G01, F2 is the combined focal length of the second lens group G02, F4 is the combined focal length of the fourth lens group G04, F is the effective focal length of the lens at infinite working distance, and H is the semi-image height of the lens.

[0065] The technical solution of the present invention can control the aperture value of the lens by adjusting the size of the aperture stop STO, and thus achieve large-aperture photography and videography. The second lens group G02 moves along the optical axis from the object side to the image side, and the fourth lens group G04 moves along the optical axis from the image side to the object side, that is, the second lens group G02 and the fourth lens group G04 move towards each other for focusing, so that the optical system of the entire lens can achieve better imaging quality under a larger aperture, thereby enabling the medium-format lens to adapt to large-aperture photography and videography. Moreover, through the combination of positive, negative, negative, positive, and negative lens groups, the lens can effectively correct various aberrations, such as spherical aberration, chromatic aberration, and distortion, etc., improve the imaging quality, and ensure the clarity and sharpness of the picture while maintaining a larger aperture.

[0066] In addition, it is designed that the second lens group G02 moves along the optical axis from the object side to the image side, and the fourth lens group G04 moves along the optical axis from the image side to the object side. This focusing method of moving towards each other is the "internal focusing" method, which can reduce the change in the total length of the lens during the focusing process, making the focusing speed faster and smoother.

[0067] It should be noted that the first lens group G01 has a positive optical power and is used to collect and initially focus light. The second lens group G02 and the fourth lens group G04 can move along the optical axis during the autofocus process to adjust the focal position. The third lens group G03 and the fifth lens group G05 have negative optical powers and can further correct light rays to improve the imaging quality. The aperture stop STO is used to control the amount of light entering the lens, thereby adjusting the exposure and depth of field.

[0068] It should be understood that by satisfying specific conditional expressions (1), (2), (3), and (4), the proportional relationships between the combined focal lengths of each lens group and the effective focal length of the lens, and between the effective focal length of the lens and the semi-image height are defined, so that the lens structure can be optimized to achieve a compact design and improve the imaging quality and focusing performance of the lens.

[0069] Specifically, setting the conditional expression (1) to define the relationship between the combined focal length of the first lens group G01 and the effective focal length of the lens at the infinite working distance helps to balance light collection and imaging quality. Exceeding the upper limit of this range will make the length of the entire first lens group G01 longer, reduce the tolerance sensitivity, but is not conducive to the miniaturization of the lens; being lower than the lower limit of this range is conducive to reducing the size and weight of the first lens group G01, but will increase the tolerance sensitivity and is not conducive to the assembly of the lens. For example, the value of F1 / F can be 0.6, 1, 1.4, 1.8, 2, 2.4, etc.

[0070] The setting condition (2) defines the relationship between the combined focal length of the second lens group G02 and the effective focal length when the lens is focused at infinity, reflecting the range of focal length variation of the second lens group G02 in the lens design. Exceeding the upper limit of this range is not conducive to correcting the chromatic aberration of the lens optical system; being lower than the lower limit of this range will increase the focusing stroke and is not conducive to miniaturizing the lens. For example, the value of F2 / F can be -3.45, -3.22, -3, -2.9, -2.5, -2.2, etc.

[0071] The setting condition (3) defines the relationship between the combined focal length of the fourth lens group G04 and the effective focal length when the lens is focused at infinity, reflecting the range of focal length variation of the fourth lens group G04 in the lens design. Exceeding the upper limit of this range is not conducive to miniaturizing the lens; being lower than the lower limit of this range is not conducive to correcting the chromatic aberration and will increase the sensitivity of assembly. For example, the value of F4 / F can be 0.55, 0.6, 0.8, 1, 1.2, 1.45, etc.

[0072] The setting condition (4) defines the relationship between the effective focal length when the lens is focused at infinity and the semi-image height of the lens, reflecting the relationship between the focal length of the lens and the imaging size, that is, the longer the focal length, the smaller the imaging (under the same sensor size). Exceeding the upper limit of this range will reduce the field of view angle, restricting the shooting range; being lower than the lower limit of this range will increase the field of view angle, which is not conducive to correcting the lens distortion and will distort the captured image. For example, the value of F / H can be 1.1, 1.6, 2, 2.2, 2.4, 2.45, etc.

[0073] In some embodiments, during the focusing process, the first lens group G01, the third lens group G03, and the fifth lens group G05 are fixed lens groups, that is, the first lens group G01, the third lens group G03, and the fifth lens group G05 remain unchanged relative to the position of the image plane IMG, so that the first lens group G01, the third lens group G03, and the fifth lens group G05 remain relatively fixed during the focusing process, which helps to maintain the overall stability and imaging consistency of the lens.

[0074] Please refer to Figure 1 and Figure 6, in some embodiments, the first lens group G01 includes, in order from the object side to the image side: a first lens L01 with negative optical power, a first optical element with positive or negative optical power, and a fourth lens L04 with positive optical power. This arrangement of multiple lenses can achieve high-quality imaging effects, including high definition, low aberration, low distortion, and low dispersion. Among them, the first optical element includes, in order from the object side to the image side, a second lens L02 with negative optical power and a third lens L03 with positive optical power, and the second lens L02 and the third lens group G03 are combined into a cemented lens; alternatively, the first optical element is a single lens. Compared with the arrangement where the first optical element is two independent lenses, it can reduce the volume and weight of the lens, making the lens more compact and portable.

[0075] It should be noted that a cemented lens is a single lens assembly formed by bonding two or more lenses together with an optical cement. Since lenses made of different materials have different degrees of light dispersion, by selecting a suitable combination of materials, a cemented lens can effectively correct chromatic aberration and improve the color reproducibility of imaging. Therefore, it has the performance of correcting chromatic aberration; moreover, the cemented lens eliminates the air gap between the lenses, reduces the reflection and scattering caused by the air gap, and improves the contrast of imaging; and by combining multiple lenses into one cemented lens, the structure of the lens can be simplified, the number and weight of the lenses can be reduced, and the lens can be made more compact and lightweight.

[0076] The lens design of the first lens group G01 will be illustrated by examples below.

[0077] Please refer to Figure 1 , in a specific example, the first lens group G01 includes, in order from the object side to the image side: a first lens L01 with negative optical power, a second lens L02 with negative optical power, a third lens L03 with positive optical power, and a fourth lens L04 with positive optical power; among them, the second lens L02 and the third lens group G03 are combined into a cemented lens with negative optical power.

[0078] Please refer to Figure 6 , in a specific example, the first lens group G01 includes, in order from the object side to the image side: a first lens L01 with negative optical power, a second lens L02 with negative optical power, a third lens L03 with positive optical power, and a fourth lens L04 with positive optical power; among them, the second lens L02 and the third lens group G03 are combined into a cemented lens with positive optical power.

[0079] The above presents two specific structural designs of the lenses of the first lens group G01, both based on the combination of four lenses. By configuring different combinations of optical powers, they can provide better imaging effects in specific application scenarios to meet specific optical design requirements.

[0080] In some embodiments, the second lens group G02 includes at least one lens with a refractive index Nd≥1.8, that is, the second lens group G02 includes at least one high-refractive-index lens, which can achieve a smaller volume and higher imaging quality of the second lens group G02. For example, the second lens group G02 may include one high-refractive-index lens, or the second lens group G02 may include two high-refractive-index lenses, etc. The refractive index Nd of the high-refractive-index lens may be 1.8, 1.82, 1.85, 1.88, 1.9, 1.95, etc.

[0081] It should be noted that the refractive index is a physical quantity that describes the degree of change in the propagation direction of light when it propagates from one medium to another. In optical lens design, materials with a high refractive index can make the lens thinner while maintaining the same focal length and optical performance, which means that using materials with a high refractive index helps to achieve a more compact lens design, reducing the volume and weight of the lens. Moreover, high-refractive-index lenses are also beneficial for eliminating spherical aberration and correcting chromatic aberration.

[0082] Please refer to Figure 1 and Figure 6 , in some embodiments, the second lens group G02 includes a second optical element with a negative optical power; wherein, the second optical element sequentially includes a fifth lens L05 with a positive optical power and a sixth lens L06 with a negative optical power from the object side to the image side, and the fifth lens L05 and the sixth lens L06 are combined into a cemented lens; or, the second optical element is a single lens. Compared with the setting where the second optical element is two independent lenses, it can reduce the volume and weight of the lens, make the lens more compact and portable, and moreover, it is also beneficial for the rapid movement of the second lens group G02.

[0083] The lens design of the second lens group G02 will be illustrated by way of example below.

[0084] Please refer to Figure 1 and Figure 6 , in a specific example, the second lens group G02 sequentially includes from the object side to the image side: a fifth lens L05 with a positive optical power and a sixth lens L06 with a negative optical power; wherein, the fifth lens L05 and the sixth lens L06 are combined into a cemented lens with a negative optical power, and the refractive index Nd of the fifth lens L05 is ≥1.8. In this specific example, the second lens group G02 has only two lenses, one of which is a high-refractive-index lens, and the two lenses are designed with positive and negative optical powers and combined into a cemented lens, which can not only optimize aberration correction and dispersion control, improve imaging quality, but also greatly reduce the volume of the focusing group and enable rapid focusing.

[0085] It should be noted that in other specific examples, the refractive index Nd of the fifth lens L05 and the sixth lens L06 can be set to be ≥ 1.8, or the refractive index Nd06 of the sixth lens L06 can be set to be ≥ 1.8.

[0086] Please refer to Figure 1 and Figure 6 , in some embodiments, the third lens group G03 includes a third optical element with a negative optical power; wherein, the third optical element sequentially includes a seventh lens L07 and an eighth lens L08 from the object side to the image side, one of the seventh lens L07 and the eighth lens L08 has a positive optical power and the other has a negative optical power, and the seventh lens L07 and the eighth lens L08 are combined into a cemented lens; or, the third optical element is a single lens. The lens design of the third lens group G03 can provide better imaging effects in specific application scenarios by configuring different combinations of optical powers to meet specific optical design requirements.

[0087] The following gives examples of the lens design of the third lens group G03.

[0088] Please refer to Figure 1 , in a specific example, the third lens group G03 sequentially includes from the object side to the image side: a seventh lens L07 with a positive optical power and an eighth lens L08 with a negative optical power; wherein, the seventh lens L07 and the eighth lens L08 are combined into a cemented lens with a negative optical power.

[0089] Please refer to Figure 6 , in another specific example, the third lens group G03 sequentially includes from the object side to the image side: a seventh lens L07 with a negative optical power and an eighth lens L08 with a positive optical power; wherein, the seventh lens L07 and the eighth lens L08 are combined into a cemented lens with a negative optical power.

[0090] The above proposes two specific structural designs of the lenses of the third lens group G03, both of which are based on the combination of two lenses. Combining the seventh lens L07 and the eighth lens L08 into a cemented lens can further reduce the number of lenses, simplify the lens structure, and make the lens more compact and portable; moreover, the seventh lens L07 and the eighth lens L08 are designed with positive and negative optical powers, which can optimize aberration correction and dispersion control and improve imaging quality.

[0091] Furthermore, the seventh lens L07 and the eighth lens L08 in the above embodiments satisfy the following conditional formula:

[0092] |Nd07 - Nd08| < 0.3, (5);

[0093] wherein, Nd07 is the refractive index of the seventh lens L07, and Nd08 is the refractive index of the eighth lens L08.

[0094] It should be understood that since the seventh lens L07 and the eighth lens L08 are combined into a cemented lens, when light passes through the cemented lens, the uneven distribution of the refractive index will cause spherical aberration in the focusing of light, affecting the imaging quality.

[0095] Specifically, conditional formula (5) defines the relationship between the refractive index of the seventh lens L07 and the refractive index of the eighth lens L08, reflecting the refractive index distribution of the cemented lens formed by the combination of the seventh lens L07 and the eighth lens L08. When it is greater than or equal to the upper limit of this range, it will be difficult to control the spherical aberration of the lens optical system. For example, the value of |Nd07 - Nd08| can be 0.298, 0.29, 0.285, 0.28, 0.2, 0.1, etc.

[0096] In some embodiments, the fourth lens group G04 includes at least one lens with an Abbe number Vd≥60, that is, the fourth lens group G04 includes at least one high-Abbe-number lens, which can reduce chromatic aberration and avoid blurring and color distortion caused by chromatic aberration, especially in the edge and wide-angle parts, thereby further improving the imaging quality of the lens. For example, the fourth lens group G04 includes one high-Abbe-number lens, or the fourth lens group G04 includes two high-Abbe-number lenses, etc.; the Abbe number Vd of the high-Abbe-number lens can be 60, 61, 62, 63, 64, 65, etc.

[0097] It should be noted that the Abbe number is a parameter describing the dispersion ability of a material, and a high Abbe number indicates less dispersion of the material. In a photographic lens, dispersion is one of the main factors causing colored fringes (i.e., the "dispersion" phenomenon) to appear at the edges of the image. Especially under a large aperture, since the refraction angle of light in the lens is larger, the dispersion phenomenon will be more obvious. By using a lens with a high Abbe number, this dispersion phenomenon can be significantly reduced, making the imaging consistency of the lens better for different colors and improving the clarity and contrast of the image.

[0098] The lens design of the fourth lens group G04 will be exemplified below.

[0099] Please refer to Figure 1 , in some embodiments, the fourth lens group G04 sequentially includes a ninth lens L09 with a positive focal power and a fourth optical element with a positive focal power from the object side to the image side; wherein, the fourth optical element sequentially includes a tenth lens L10 with a positive focal power and an eleventh lens L11 with a negative focal power from the object side to the image side, and the tenth lens L10 and the eleventh lens L11 are combined into a cemented lens; or, the fourth optical element is a single lens. At least one of the ninth lens L09 and the tenth lens L10 has an Abbe number Vd≥60 with respect to light with a wavelength of 587.6 nm.

[0100] Please continue to refer toFigure 1 , in a specific example, the fourth lens group G04 includes, in order from the object side to the image side: a ninth lens L09 with a positive focal power, a tenth lens L10 with a positive focal power, and an eleventh lens L11 with a negative focal power. Among them, the tenth lens L10 and the eleventh lens L11 are combined into a cemented lens with a positive focal power, and the Abbe number Vd of the ninth lens L09 and the tenth lens L10 is ≥ 60.

[0101] It should be noted that in other specific examples, the Abbe number Vd09 of the ninth lens L09 can be set to ≥ 60, or the Abbe number Vd10 of the tenth lens L10 can be set to ≥ 60, etc.

[0102] Please refer to Figure 6 , the fourth lens group G04 includes, in order from the object side to the image side: a fifth optical element with a positive focal power and an eleventh lens L11 with a positive focal power; among them, the fifth optical element includes, in order from the object side to the image side, a ninth lens L09 with a negative focal power and a tenth lens L10 with a positive focal power, and the ninth lens L09 and the tenth lens L10 are combined into a cemented lens; or the fifth optical element is a single lens. The Abbe number Vd of at least one of the tenth lens L10 and the eleventh lens L11 with respect to light of wavelength 587.6 nm is ≥ 60.

[0103] Please continue to refer to Figure 6 , in a specific example, the fourth lens group G04 includes, in order from the object side to the image side: a ninth lens L09 with a negative focal power, a tenth lens L10 with a positive focal power, and an eleventh lens L11 with a positive focal power. Among them, the ninth lens L09 and the tenth lens L10 are combined into a cemented lens with a positive focal power, and the Abbe number Vd of the tenth lens L10 and the eleventh lens L11 is ≥ 60.

[0104] It should be noted that in other specific examples, the Abbe number Vd11 of the eleventh lens L11 can be set to ≥ 60, or the Abbe number Vd10 of the tenth lens L10 can be set to ≥ 60, etc.

[0105] The above proposes two specific structural designs of the lenses of the fourth lens group G04, both of which are based on the combination of three lenses. By configuring different focal power combinations, they can provide better imaging effects in specific application scenarios to meet specific optical design requirements. Moreover, based on the setting of high-Abbe-number lenses, the imaging quality of the lens can be improved; based on the setting of combined cemented lenses, not only can the volume and weight of the lens be reduced, making the lens more compact and portable, but also the volume of the focusing group can be greatly reduced, enabling rapid focusing.

[0106] In some embodiments, the fifth lens group G05 includes at least one lens with a refractive index Nd≥1.8, that is, the fifth lens group G05 includes at least one high-refractive-index lens, which can achieve a smaller volume and higher imaging quality of the fifth lens group G05. For example, the fifth lens group G05 may include one high-refractive-index lens, or the fifth lens group G05 may include two high-refractive-index lenses, etc. The refractive index Nd of the high-refractive-index lens may be 1.8, 1.82, 1.85, 1.88, 1.9, 1.95, etc.

[0107] The lens design of the fifth lens group G05 will be illustrated by way of example below.

[0108] Please refer to Figure 1 , in a specific example, the fifth lens group G05 includes, in order from the object side to the image side: a twelfth lens L12 with a positive optical power, a thirteenth lens L13 with a negative optical power, a fourteenth lens L14 with a negative optical power, and a fifteenth lens L15 with a positive optical power; wherein, the refractive indices Nd of the twelfth lens L12, the fourteenth lens L14, and the fifteenth lens L15 are ≥1.8.

[0109] According to actual needs, in other specific examples, the refractive index Nd12 of the twelfth lens L12 may be set to ≥1.8, or the refractive indices Nd of the fourteenth lens L14 and the fifteenth lens L15 may be ≥1.8, etc.

[0110] Please refer to Figure 6 , in some embodiments, the fifth lens group G05 includes, in order from the object side to the image side: a twelfth lens L12 with a positive optical power, a sixth optical element with a negative optical power, and a fifteenth lens L15 with a negative optical power; wherein, the sixth optical element includes, in order from the object side to the image side, a thirteenth lens L13 with a positive optical power and a fourteenth lens L14 with a negative optical power, and the thirteenth lens L13 and the fourteenth lens L14 are combined into a cemented lens; or, the sixth optical element is a single lens. At least one of the twelfth lens L12 and the fifteenth lens L15 has a refractive index Nd≥1.8.

[0111] Please continue to refer to Figure 6 , in a specific example, the fifth lens group G05 includes, in order from the object side to the image side: a twelfth lens L12 with a positive optical power, a thirteenth lens L13 with a positive optical power, a fourteenth lens L14 with a negative optical power, and a fifteenth lens L15 with a negative optical power. Among them, the thirteenth lens L13 and the fourteenth lens L14 are combined into a cemented lens with a negative optical power, and the refractive indices Nd of the twelfth lens L12 and the fifteenth lens L15 are ≥1.8.

[0112] According to actual needs, the refractive index Nd12 of the twelfth lens L12 can be set to Nd12 ≥ 1.8, or the refractive index Nd of the fourteenth lens L14 and the fifteenth lens L15 can be set to Nd ≥ 1.8, etc.

[0113] The above presents two specific structural designs of the fifth lens group G05. Based on a combination of multiple lenses, by configuring different combinations of optical powers, it can provide better imaging effects in specific application scenarios to meet specific optical design requirements. Moreover, based on the setting of high-refractive-index lenses, the imaging quality of the lens can be improved; based on the setting of combined cemented lenses, not only can the volume and weight of the lens be reduced, making the lens more compact and portable, but also the mechanical stability and reliability of the lens can be improved.

[0114] Please refer to Figure 1 and Figure 6 , in some embodiments, at least two aspherical lenses are included in the lenses of the first lens group G01, the second lens group G02, the third lens L03, the fourth lens group G04, and the fifth lens group G05, which can effectively shorten the length of the system and improve the imaging quality. For example, one aspherical lens is provided in each of the first lens group G01 and the fifth lens group G05, or two aspherical lenses are provided in the fifth lens group G05, or two aspherical lenses are provided in the first lens group G01 and one aspherical lens is provided in the fifth lens group G05.

[0115] It should be noted that aspherical lenses are relative to traditional spherical lenses. Traditional spherical lenses are relatively simple in design and manufacture, but due to the constant curvature radius of their surfaces, this will cause aberration when light passes through the lens, especially at the edge part. Aspherical lenses, on the other hand, modify the curvature of the lens surface so that light can pass through the lens more evenly, thereby effectively reducing or eliminating these aberrations, making the image edge clearer, improving sharpness, and making the focus more accurate, thus achieving high-quality imaging under a large aperture. Therefore, aspherical lenses can achieve a large aperture and improve sharpness, and when designing a lens, the number and thickness of lenses can also be reduced through aspherical lenses, thereby reducing the volume and weight of the lens.

[0116] Please refer to Figure 1 and Figure 6 , in some embodiments, a parallel glass plate GL configured by a kind of filter is arranged between the last lens of the fifth lens group G05 and the image plane IMG. The function of the parallel glass plate GL is to filter light to improve the imaging quality. Specifically, it can absorb or reflect light of certain wavelengths to eliminate or reduce interference factors such as chromatic aberration and stray light, thereby improving the contrast and clarity of the image.

[0117] The following presents specific embodiments of a large-aperture medium-format wide-angle autofocus lens.

[0118] Example 1

[0119] Please refer to Figure 1 , Figure 1 , which is a schematic structural diagram of the large-aperture medium-format wide-angle autofocus lens provided in this embodiment. The first lens group G01 includes, in order from the object side to the image side, a first lens L01 with a negative focal power, a second lens L02 with a negative focal power, a third lens L03 with a positive focal power, and a fourth lens L04 with a positive focal power; among them, the second lens L02 and the third lens group G03 form a cemented lens with a negative focal power, and the fourth lens L04 is an aspherical lens. The second lens group G02 includes, in order from the object side to the image side, a fifth lens L05 with a positive focal power and a sixth lens L06 with a negative focal power; among them, the fifth lens L05 and the sixth lens L06 form a cemented lens with a negative focal power, and the refractive index Nd of the fifth lens L05 is 1.92. The third lens group G03 includes, in order from the object side to the image side, a seventh lens L07 with a positive focal power and an eighth lens L08 with a negative focal power; among them, the seventh lens L07 and the eighth lens L08 form a cemented lens with a negative focal power, the refractive index Nd07 of the seventh lens L07 is 1.59, and the refractive index Nd08 of the eighth lens L08 is 1.67. The fourth lens group G04 includes, in order from the object side to the image side, a ninth lens L09 with a positive focal power, a tenth lens L10 with a positive focal power, and an eleventh lens L11 with a negative focal power; among them, the tenth lens L10 and the eleventh lens L11 form a cemented lens with a positive focal power, the Abbe number Vd of the ninth lens L09 is 68.62, and the Abbe number Vd of the tenth lens L10 is 68.62. The aperture stop STO is located between the eighth lens L08 and the ninth lens L09. The fifth lens group G05 includes, in order from the object side to the image side, a twelfth lens L12 with a positive focal power, a thirteenth lens L13 with a negative focal power, a fourteenth lens L14 with a negative focal power, and a fifteenth lens L15 with a positive focal power; among them, the refractive index Nd of the twelfth lens L12 is 1.95, the refractive index Nd of the fourteenth lens L14 is 1.81, the refractive index Nd of the fifteenth lens L15 is 1.83, and the fourteenth lens L14 is an aspherical lens.

[0120] In this embodiment, the numerical data of the large-aperture medium-format wide-angle autofocus lens are shown in Tables 1 and 2:

[0121] Table 1

[0122]

[0123] Table 2

[0124]

[0125] Among them, the surface numbers represent the surface numbers of the lenses from the object side to the image side.

[0126] Please refer to Figures 2 to 5 , Figure 2 which is the axial chromatic aberration curve graph when the lens is focused at infinity, Figure 3 which is the schematic diagram of field curvature and distortion when the lens is focused at infinity, Figure 4 which is the axial chromatic aberration curve graph when the lens is focused at the nearest focusing distance, Figure 5 which is the schematic diagram of field curvature and distortion when the lens is focused at the nearest focusing distance. It can be seen from Figures 2 to 5 that the lens of Embodiment 1 has a good imaging effect.

[0127] It should be noted that the axial chromatic aberration curve graph represents the axial chromatic aberration curve at an f-number of 1.47. Among them, the F line, D line, and C line respectively represent the axial chromatic aberration at wavelengths of 486 nm, 587 nm, and 656 nm. The abscissa represents the magnitude of the spherical aberration value, and the ordinate represents the field of view. The field curvature curve graph represents the field curvature curve at a semi-field angle ω of 14.02°. Among them, the dashed line S represents the value of the chief ray D line on the sagittal image plane, and the solid line T represents the value of the chief ray D line on the meridional image plane. The abscissa represents the magnitude of the field curvature value, and the ordinate represents the field of view. The distortion curve graph represents the distortion curve at a semi-field angle ω of 14.02°. Among them, the abscissa represents the distortion value, and the ordinate represents the field of view.

[0128] It should be understood that the above descriptions of various spherical aberration, field curvature, and distortion curve graphs are the same as those of other embodiments and will not be repeated hereinafter.

[0129] Embodiment 2

[0130] Please refer to Figure 6 , Figure 6It is a schematic structural diagram of a large-aperture medium-format wide-angle autofocus lens provided in this embodiment. The first lens group G01 includes, in order from the object side to the image side, a first lens L01 with negative optical power, a second lens L02 with negative optical power, a third lens L03 with positive optical power, and a fourth lens L04 with positive optical power; among them, the second lens L02 and the third lens group G03 are combined into a cemented lens with positive optical power, and the fourth lens L04 is an aspherical lens. The second lens group G02 includes, in order from the object side to the image side, a fifth lens L05 with positive optical power and a sixth lens L06 with negative optical power; among them, the fifth lens L05 and the sixth lens L06 are combined into a cemented lens with negative optical power, and the refractive index Nd of the fifth lens L05 is 1.95. The third lens group G03 includes, in order from the object side to the image side, a seventh lens L07 with negative optical power and an eighth lens L08 with positive optical power; among them, the seventh lens L07 and the eighth lens L08 are combined into a cemented lens with negative optical power, the refractive index Nd07 of the seventh lens L07 is 1.67, and the refractive index Nd08 of the eighth lens L08 is 1.59. The fourth lens group G04 includes, in order from the object side to the image side, a ninth lens L09 with negative optical power, a tenth lens L10 with positive optical power, and an eleventh lens L11 with positive optical power; among them, the ninth lens L09 and the tenth lens L10 are combined into a cemented lens with positive optical power, the Abbe number Vd of the tenth lens L10 is 68.62, and the Abbe number Vd of the eleventh lens L11 is 68.62. The aperture stop STO is disposed between the eighth lens L08 and the ninth lens L09. The fifth lens group G05 includes, in order from the object side to the image side, a twelfth lens L12 with positive optical power, a thirteenth lens L13 with positive optical power, a fourteenth lens L14 with negative optical power, and a fifteenth lens L15 with negative optical power; among them, the thirteenth lens L13 and the fourteenth lens L14 are combined into a cemented lens with negative optical power, the refractive index Nd of the twelfth lens L12 is 1.95, the refractive index Nd of the fifteenth lens L15 is 1.85, and the fifteenth lens L15 is an aspherical lens.

[0131] In this embodiment, the numerical data of the large-aperture medium-format wide-angle autofocus lens are shown in Tables 3 and 4:

[0132] Table 3

[0133]

[0134] Table 4

[0135]

[0136] Among them, the surface number indicates the surface numbers of each lens from the object side to the image side.

[0137] Please refer to Figures 7 to 10 , Figure 7 which is the axial chromatic aberration curve graph when the lens is focused at infinity, Figure 8 and Figure 9 which is the schematic diagram of field curvature and distortion when the lens is focused at infinity, Figure 10 and Figures 7 to 10 which is the axial chromatic aberration curve graph when the lens is focused at the nearest focusing distance,

[0138] and

[0138] which is the schematic diagram of field curvature and distortion when the lens is focused at the nearest focusing distance. It can be seen from Figures 7 to 10 that the lens of Embodiment 2 has good imaging effect.

[0138] The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A large aperture medium format wide angle autofocus lens, characterized in that: The lens is composed of, from the object side to the image side, a first lens group having positive power, a second lens group having negative power, a third lens group having negative power, an aperture stop, a fourth lens group having positive power, and a fifth lens group having negative power; The first lens group is composed of a first lens with negative power, a second lens with negative power, a third lens with positive power, and a fourth lens with positive power in order from the object side to the image side; the second lens group is composed of a fifth lens with positive power and a sixth lens with negative power in order from the object side to the image side; the third lens group is composed of a seventh lens with positive power and an eighth lens with negative power in order from the object side to the image side; the fourth lens group is composed of a ninth lens with positive power, a tenth lens with positive power, and an eleventh lens with negative power in order from the object side to the image side; the fifth lens group is composed of a twelfth lens with positive power, a thirteenth lens with negative power, a fourteenth lens with negative power, and a fifteenth lens with positive power in order from the object side to the image side; or, The first lens group is composed of a first lens with negative power, a second lens with negative power, a third lens with positive power, and a fourth lens with positive power in order from the object side to the image side; the second lens group is composed of a fifth lens with positive power and a sixth lens with negative power in order from the object side to the image side; the third lens group is composed of a seventh lens with negative power and an eighth lens with positive power in order from the object side to the image side; the fourth lens group is composed of a ninth lens with negative power, a tenth lens with positive power, and an eleventh lens with positive power in order from the object side to the image side; the fifth lens group is composed of a twelfth lens with positive power, a thirteenth lens with positive power, a fourteenth lens with negative power, and a fifteenth lens with negative power in order from the object side to the image side; During the focusing process, the second lens group moves along the optical axis from the object side to the image side, and the fourth lens group moves along the optical axis from the image side to the object side; The large aperture medium format wide angle autofocus lens satisfies the following conditional formula: 0.5<F1 / F<2.5; -3.5<F2 / F<-2; 0.5<F4 / F<1.5; 1<F / H<2.5; Among them, F1 is the synthetic focal length of the first lens group, F2 is the synthetic focal length of the second lens group, F4 is the synthetic focal length of the fourth lens group, F is the effective focal length of the lens at infinite working distance, and H is the half image height of the lens.

2. The large aperture medium format wide angle autofocus lens according to claim 1, characterized in that: The lenses of the first lens group, the second lens group, the third lens group, the fourth lens group, and the fifth lens group include at least two aspherical lenses.

3. The large aperture medium format wide angle autofocus lens according to claim 1, characterized in that: During the focusing process, the first lens group, the third lens group, and the fifth lens group are fixed lens groups.

4. The large aperture medium format wide angle autofocus lens according to claim 1, characterized in that: The second lens and the third lens are combined into a cemented lens.

5. The large aperture medium format wide angle autofocus lens according to claim 1, characterized in that: The second lens group includes at least one lens with a refractive index Nd≥1.

8.

6. The large aperture medium format wide angle autofocus lens according to claim 1, characterized in that: The fifth lens and the sixth lens are combined into a cemented lens.

7. The large aperture medium format wide angle autofocus lens according to claim 1, characterized in that: The seventh lens and the eighth lens satisfy the following conditional formula: |Nd07-Nd08|<0.3; Wherein, Nd07 is the refractive index of the seventh lens, and Nd08 is the refractive index of the eighth lens.

8. The large aperture medium format wide angle autofocus lens according to claim 1, characterized in that: The seventh lens and the eighth lens are combined into a cemented lens.

9. The large aperture medium format wide angle autofocus lens according to any one of claims 1 to 8, characterized in that: The fourth lens group includes at least one lens with an Abbe number Vd≥60.

10. The large aperture medium format wide angle autofocus lens according to claim 1, characterized in that: When the fourth lens group consists of a ninth lens having positive power, a tenth lens having positive power and an eleventh lens having negative power in sequence from the object side to the image side, the tenth lens and the eleventh lens are combined into a cemented lens.

11. The large aperture medium format wide angle autofocus lens according to claim 1, characterized in that: When the fourth lens group consists of a ninth lens having negative power, a tenth lens having positive power and an eleventh lens having positive power in sequence from the object side to the image side, the ninth lens and the tenth lens are combined into a cemented lens.

12. The large aperture medium format wide angle autofocus lens according to claim 1, characterized in that: The fifth lens group includes at least one lens with a refractive index Nd≥1.

8.

13. The large aperture medium format wide angle autofocus lens according to claim 1, characterized in that: When the fifth lens group consists of a twelfth lens with positive refractive power, a thirteenth lens with positive refractive power, a fourteenth lens with negative refractive power, and a fifteenth lens with negative refractive power in sequence from the object side to the image side, the thirteenth lens and the fourteenth lens are combined into a cemented lens.

14. An image pickup device, characterized in that: The invention comprises an image sensor and the large aperture medium format wide angle autofocus lens according to any one of claims 1 to 13, wherein the image sensor is configured to receive an optical image formed by the large aperture medium format wide angle autofocus lens.

Images