An internal focusing photographic lens

Abstract

The utility model discloses an inner focusing photographic lens. The lens comprises a first lens group with positive focal length, a second lens group with positive focal length and a third lens group with positive or negative focal length arranged in order along the optical axis from the object side to the image side; the second lens group is a focusing group of the inner focusing photographic lens, the first lens group and the third lens group are fixed groups of the inner focusing photographic lens, the first lens group comprises at least one meniscus lens, and in the focusing process of the object distance from far to near, the focusing group moves to the object side along the optical axis; the focal length of the first lens group and the focal length of the inner focusing photographic lens satisfy: 2 < F1 / F < 6.96; wherein, F1 represents the focal length of the first lens group, and F represents the focal length of the inner focusing photographic lens. The utility model realizes the inner focusing photographic lens design of high image quality and small volume by matching the lens material and reasonably distributing the focal length of each element, and the object distance range of 120mm~inf can be imaged well.

Description

Technical Field

[0001] This utility model relates to the field of lens technology, and in particular to an internal focusing photographic lens. Background Technology

[0002] In recent years, the mirrorless camera market has continued to grow, gradually replacing DSLRs as the mainstream, achieving breakthroughs in lightweight body design and electronic viewfinder technology. With its compact design and DSLR-like image quality, mirrorless cameras have quickly become an important category in the photography market and have driven technological innovation in the camera industry. The global market share of mirrorless cameras has surpassed that of DSLRs, especially among amateur and professional photographers. However, the rise of smartphone photography has squeezed the entry-level camera market, forcing mirrorless camera manufacturers to shift towards high-end and professional models.

[0003] The image quality of camera lenses on the market varies greatly. Some lenses with clear images and good image quality are too large, making them inconvenient to carry and use by photographers; others have a narrow object distance range, resulting in blurry close-up shots that make it impossible to distinguish actual objects. Utility Model Content

[0004] This invention provides an internal focusing photographic lens. By combining lens materials and rationally allocating the optical power of each component, it achieves an internal focusing photographic lens design that balances high image quality and small size, and can produce good images in the object distance range of 120mm to inf (infinity).

[0005] According to one aspect of the present invention, an internal focusing photographic lens is provided, comprising a first lens group with positive optical power, a second lens group with positive optical power, and a third lens group with positive or negative optical power arranged sequentially along the optical axis from the object side to the image side. The second lens group is the focusing group of the internal focusing camera lens, and the first lens group and the third lens group are the fixed groups of the internal focusing camera lens. The first lens group includes at least one meniscus lens. During the focusing process from far to near the object distance, the focusing group moves along the optical axis to the object side. The focal length of the first lens group and the focal length of the internal focusing camera lens satisfy the following: 2 <F1 / F<6.96; Wherein, F1 represents the focal length of the first lens group, and F represents the focal length of the internal focusing camera lens.

[0006] Optionally, the focal length of the second lens group and the focal length of the internal focusing camera lens satisfy the following: 1.3 <F2 / F<2.6; Wherein, F2 represents the focal length of the second lens group, and F represents the focal length of the internal focusing camera lens.

[0007] Optionally, the optical back focal distance and total optical length of the internal focusing camera lens satisfy the following: 0.18 <BF / TTL<0.25; Wherein, BF represents the optical back focal distance of the internal focusing camera lens, and TTL represents the total optical length of the internal focusing camera lens.

[0008] Optionally, the maximum effective aperture and total optical length of the internal focusing camera lens satisfy the following: 0.35 <SD / TTL<0.41; Wherein, SD represents the maximum effective aperture of the internal focusing camera lens, and TTL represents the total optical length of the internal focusing camera lens.

[0009] Optionally, the first lens group includes a first lens, a second lens, a third lens, a fourth lens, and a fifth lens arranged sequentially from the object side to the image side; the second lens group includes a sixth lens, a seventh lens, and an eighth lens arranged sequentially from the object side to the image side; and the third lens group includes a ninth lens and a tenth lens arranged sequentially from the object side to the image side.

[0010] Optionally, the fourth and fifth lenses can be used separately or combined to form a cemented lens, the sixth lens has positive optical power, the seventh lens is a meniscus lens bent towards the image side, and the eighth lens is a meniscus lens bent towards the object side.

[0011] Optionally, the Abbe number vd6 of the sixth lens satisfies: vd6≥53.

[0012] Optionally, the refractive index nd4 of the fourth lens satisfies: nd4≥1.8.

[0013] Optionally, the second lens and the eighth lens are both plastic aspherical lenses, and the first lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens, the ninth lens and the tenth lens are all glass spherical lenses.

[0014] Optionally, an aperture stop is also included, which is located between the first lens group and the second lens group.

[0015] The internal focusing photographic lens provided in this embodiment includes a first lens group with positive optical power, a second lens group with positive optical power, and a third lens group with positive or negative optical power arranged sequentially from the object side to the image side along the optical axis; the second lens group is the focusing group of the internal focusing photographic lens, and the first and third lens groups are the fixing groups of the internal focusing photographic lens; the first lens group contains at least one meniscus lens; during the focusing process from far to near object distance, the focusing group moves along the optical axis to the object side. The internal focusing photographic lens provided in this embodiment of the invention can effectively control the angle and direction of light by controlling the optical power of the lenses in the first lens group, avoiding excessive divergence of light entering the lens, thereby reducing the generation of off-axis aberrations in the system, which is beneficial to improving the image quality of the photographic lens and also facilitates a smooth transition of light at the rear of the lens, resulting in better tolerances for individual lenses and assembly. In addition, the first lens group includes at least one meniscus lens, which can better correct the field curvature of the system. By moving the position of the second lens group on the optical axis, focusing can be achieved at different object distances. Good imaging can be achieved in the object distance range of 120mm to inf, realizing an internal focusing photographic lens design that can balance high image quality and small size.

[0016] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of this utility model, nor is it intended to limit the scope of this utility model. Other features of this utility model will become readily apparent from the following description. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this utility model, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A schematic diagram of the structure of an internal focusing photographic lens provided in an embodiment of this utility model; Figure 2 A transverse chromatic aberration diagram of an internal focusing photographic lens at infinity object distance, provided for an embodiment of this utility model; Figure 3 A field curvature distortion curve of an internal focusing photographic lens at infinity object distance is provided for an embodiment of this utility model; Figure 4 An axial aberration diagram of an internal focusing photographic lens at infinity object distance, provided for an embodiment of this utility model; Figure 5 A schematic diagram of another internal docking camera lens provided in an embodiment of this utility model; Figure 6Another transverse chromatic aberration diagram of an internal focusing photographic lens at infinity object distance, provided for an embodiment of this utility model; Figure 7 Another field curvature distortion curve of an internal focusing photographic lens at infinity object distance, provided for an embodiment of this utility model; Figure 8 Another axial aberration diagram of an internal focusing photographic lens at infinity object distance provided in this embodiment of the present invention; Figure 9 A schematic diagram of the structure of another internal docking camera lens provided in this embodiment of the utility model; Figure 10 Another transverse chromatic aberration diagram of an internal focusing photographic lens at infinity object distance provided in this embodiment of the present invention; Figure 11 Another field curvature distortion curve of an internal focusing photographic lens at infinity object distance provided for an embodiment of this utility model; Figure 12 This is another example of an internal focusing photographic lens with an axial aberration at infinity, provided as an embodiment of the present invention. Detailed Implementation

[0019] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0020] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this utility model are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the utility model described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0021] Figure 1 This is a schematic diagram of the structure of an internal focusing photographic lens provided in an embodiment of the present invention, with reference to... Figure 1, the inner-focusing photographic lens comprises, arranged in order along an optical axis from an object side to an image side, a first lens group (10) with positive refractive power, a second lens group (20) with positive refractive power, and a third lens group (30) with positive refractive power or negative refractive power; the second lens group (20) is a focusing group of the inner-focusing photographic lens, the first lens group (10) and the third lens group (30) are fixed groups of the inner-focusing photographic lens, the first lens group (10) comprises at least one meniscus lens, and during a focusing process where the object distance changes from far to near, the focusing group moves along the optical axis toward the object side; The focal length of the first lens group (10) and the focal length of the inner-focusing photographic lens satisfy: 2<F1 / F<6.96; wherein F1 represents the focal length of the first lens group (10), and F represents the focal length of the inner-focusing photographic lens.

[0022] It can be understood that refractive power is the reciprocal of focal length, which characterizes the ability of an optical system to bend light. A larger absolute value of refractive power indicates a stronger ability to bend light, while a smaller absolute value of refractive power indicates a weaker ability to bend light. When refractive power is positive, the refraction of light is convergent; when refractive power is negative, the refraction of light is divergent. In specific implementation, with reference to Figure 1 , the inner-focusing photographic lens further comprises a stop (40), and the stop (40) is located between the first lens group (10) and the second lens group (20). The stop (40) can be used to block light far from the optical axis, thereby improving image quality. The inner-focusing photographic lens may further comprise a flat glass (50), the flat glass (50) is arranged at a side closest to an image plane, and the flat glass (50) can protect a photosensitive chip in an image sensor, wherein the photosensitive chip is configured to convert optical signals collected by the inner-focusing photographic lens into electrical signals, thereby ensuring the imaging effect of the inner-focusing photographic lens. The first lens group (10), the stop (40), the second lens group (20), the third lens group (30) and the flat glass (50) can be arranged in a lens barrel ( Figure 1 not shown herein), positions of the first lens group (10) and the third lens group (30) are fixed, and focusing of the lens at different object distances is realized through movement of the second lens group (20). It should be noted that, Figure 1 the structural schematic diagrams corresponding to this embodiment and subsequent embodiments are only structural illustrations, and shapes such as aspheric surfaces are not represented according to actual conditions.

[0023] By setting the focal length of the first lens group (10) and the focal length of the inner-focusing photographic lens to satisfy 2<F1 / F<6.96, the refractive power of lenses at the front end of the stop is controlled, which can effectively constrain the angle and propagation trend of light, avoid excessively divergent angles of light entering the lens, thereby reducing off-axis aberration of the system, and facilitating improvement of the image quality of the photographic lens. It also facilitates smooth transition of light at the rear end of the lens, resulting in good tolerance of single lens tolerance and assembly tolerance. In addition, the first lens group (10) in front of the stop (40) comprises at least one meniscus lens, which can better correct field curvature of the system.

[0024] Optionally, the focal length of the second lens group 20 and the focal length of the internal focusing camera lens satisfy the following: 1.3 <F2 / F<2.6; Where F2 represents the focal length of the second lens group 20, and F represents the focal length of the internal focusing camera lens.

[0025] If the upper limit of the above-mentioned limit is exceeded, the refractive power of the second lens group 20 will be too weak, making it impossible to meet the focusing state at different object distances within the limited length range, thus affecting near-object distance imaging. If the lower limit of the above-mentioned limit is exceeded, the refractive power of the second lens group 20 will become stronger, which will make it easier to meet the focusing state at different object distances, but at the same time, it will also cause the second lens group 20 to produce larger aberrations, which will have an adverse effect on the overall aberration correction of the system, and the amount of residual aberration correction that the system needs to bear will increase.

[0026] Optionally, the optical back focal distance and total optical length of the internal focusing camera lens satisfy the following: 0.18 <BF / TTL<0.25; Where BF represents the optical back focal distance of the internal focusing camera lens, and TTL represents the total optical length of the internal focusing camera lens.

[0027] By limiting the relationship between the lens's optical back focal length and its overall optical length, the lens can maintain a relatively short overall length and a compact structure while having a sufficiently long back focal length for easy installation.

[0028] Optionally, the maximum effective aperture and total optical length of the internal focusing camera lens must meet the following requirements: 0.35 <SD / TTL<0.41; Wherein, SD represents the maximum effective aperture of the internal focusing camera lens, and TTL represents the total optical length of the internal focusing camera lens.

[0029] By controlling the size of the lens aperture, the lens size is prevented from being too large, effectively limiting the weight of the optical system, controlling costs, and further preventing the overall length of the lens from being too long due to an excessively large aperture, which helps to reduce the lens size.

[0030] Continue to refer to Figure 1 Optionally, the first lens group 10 includes a first lens 101, a second lens 102, a third lens 103, a fourth lens 104, and a fifth lens 105 arranged sequentially from the object side to the image side; the second lens group 20 includes a sixth lens 201, a seventh lens 202, and an eighth lens 203 arranged sequentially from the object side to the image side; and the third lens group 30 includes a ninth lens 301 and a tenth lens 302 arranged sequentially from the object side to the image side.

[0031] Optionally, the second lens 102 and the eighth lens 203 are both plastic aspherical lenses, while the first lens 101, the third lens 103, the fourth lens 104, the fifth lens 105, the sixth lens 201, the seventh lens 202, the ninth lens 301 and the tenth lens 302 are all glass spherical lenses.

[0032] The technical solution of this embodiment uses 10 lenses to form an 8G2P (8 glass 2 plastic) structure. By comprehensively designing the optical power of each lens, clear imaging can be achieved in the object distance range of 120mm to inf.

[0033] Optionally, the fourth lens 104 and the fifth lens 105 can be used separately or combined to form a cemented lens, the sixth lens 201 has positive optical power, the seventh lens 202 is a meniscus lens bent towards the image side, and the eighth lens 203 is a meniscus lens bent towards the object side.

[0034] Optionally, the Abbe number vd6 of the sixth lens 201 satisfies: vd6≥53.

[0035] By designing the sixth lens 201 as a high Abbe number lens, it was found that high Abbe number lenses offer excellent control over chromatic aberration, promoting the actual focusing of light of various wavelengths at the same point and significantly reducing color distortion. Through the characteristic of low-dispersion wavelengths, and by combining it with other lenses using appropriate materials, chromatic aberration was reduced, and image sharpness and color reproduction were improved.

[0036] Optionally, the refractive index nd4 of the fourth lens 104 satisfies: nd4≥1.8.

[0037] By designing the fourth lens 104 as a high-refractive-index lens, the high-refractive-index lens has a better ability to refract light, enabling the lens to meet imaging requirements even with a limited overall length. In addition, using a high-refractive-index lens can reduce the thickness of the lens, which is beneficial for reducing the size and weight of the lens.

[0038] The internal focusing photographic lens provided in this embodiment of the invention can effectively control the angle and direction of light by controlling the optical power of the lenses in the first lens group, avoiding excessive divergence of light entering the lens, thereby reducing the generation of off-axis aberrations in the system, which is beneficial to improving the image quality of the photographic lens and also facilitates a smooth transition of light at the rear of the lens, resulting in better tolerances for individual lenses and assembly. In addition, the first lens group includes at least one meniscus lens, which can better correct the field curvature of the system. By moving the position of the second lens group on the optical axis, focusing can be achieved at different object distances. Good imaging can be achieved in the object distance range of 120mm to inf, realizing an internal focusing photographic lens design that can balance high image quality and small size.

[0039] In this embodiment of the invention, the aspherical lens surface of the internal focusing photographic lens satisfies the following formula: Where z is the axial distance from the vertex of the surface at a position perpendicular to the optical axis at a height r along the optical axis; c represents the curvature at the vertex of the aspherical surface; k is the fitted conic coefficient; and A, B, and C are the fourth, sixth, and eighth order higher-order aspherical coefficients corresponding to the aspherical surface.

[0040] For example, Table 1 shows the relationship with Figure 1 The specific parameters of the corresponding internal focusing camera lens are as follows: In this embodiment, the lens focal length is 22.12mm: Table 1. Specific parameters of internal focusing photography lenses Table 2 is... Figure 1 The specific design parameters of each lens in the internal focusing camera lens are as follows: Table 2 Design values ​​of lens parameters for internal focusing photography lenses In Table 2, the surface numbers are assigned according to the surface sequence of each lens. Surface number 0 represents the object plane, 11 represents the aperture stop of an internal focusing camera lens, and 24 represents the image plane. The radius of curvature represents the curvature of the corresponding lens surface. A positive value indicates that the surface bends towards the image plane, and a negative value indicates that the surface bends towards the object plane. "INF" indicates that the surface is flat and the radius of curvature is infinite. D1 and D2 represent the focusing interval, and the thickness represents the central axial distance between the current surface and the next surface. The units for both the radius of curvature and the thickness are millimeters. The refractive index nd determines the ability of the material between the current surface and the next surface to deflect light. A blank space indicates that the current position is air and the refractive index is 1. The Abbe number vd determines the dispersion characteristics of the material between the current surface and the next surface.

[0041] Table 3 shows the focus interval values ​​in Table 2 (this focus interval limit ensures clear imaging at different object distances): Table 3. One design value for the focus interval of an internal focusing photographic lens. Table 4 is... Figure 1 Aspherical surface parameters in in-center focusing lenses: Table 4 Aspherical parameters of internal focusing lenses Where -1.26934843E-04 indicates that the A coefficient of face number 3 is -1.26934843 × 10 -4 .

[0042] Figure 2This invention provides a transverse chromatic aberration diagram of an internally focused photographic lens at infinity. The horizontal axis of the diagram represents the Y-coordinate difference of the principal rays at different wavelengths on the image plane, and the vertical axis represents the field of view. The greater the deviation of the curve from the zero baseline, the more significant the chromatic aberration. Figure 2 It can be seen that the vertical chromatic aberration of the lens in this embodiment is within 10μm, and the vertical chromatic aberration is well corrected.

[0043] Figure 3 A field curvature distortion curve of an internal focusing camera lens at infinity object distance is provided for an embodiment of this utility model. Figure 3 In the left-hand coordinate system, the horizontal coordinate represents the magnitude of the field curvature in mm; the vertical coordinate represents the normalized image height, which has no unit; where T represents the meridion and S represents the sagitta; Figure 3 As shown in the left figure, the lens provided in this embodiment effectively controls field curvature, meaning that the difference in image quality between the center and the periphery is small during imaging; in the coordinate system on the right, the horizontal axis represents the magnitude of distortion, expressed as a percentage, and the vertical axis represents the normalized image height, which has no unit; Figure 3 As can be seen from the right figure, the distortion of the lens provided in this embodiment has been well corrected, and the imaging distortion is small.

[0044] Figure 4 This embodiment of the invention provides an axial aberration diagram of an internally focused photographic lens at infinity object distance. The horizontal axis represents the focal position, and the vertical axis represents the normalized pupil size. Each line represents a different wavelength, used to analyze the focusing differences of different wavelengths of light. The difference in focal position between different wavelengths of light reflects the dispersive characteristics of the optical system. If different wavelengths of light are focused at the same position, it indicates low dispersiveness; conversely, it indicates high dispersiveness. Figure 4 It can be seen that the focal shift variation of different wavelengths is within 70μm, and the system has a small chromatic difference.

[0045] Figure 5 Table 5 shows a schematic diagram of another internal docking camera lens provided in this embodiment of the present invention. Figure 5 The specific parameters of the corresponding internal focusing camera lens are as follows: In this embodiment, the lens focal length is 21.35mm: Table 5 Specific parameters of internal focusing photography lenses Table 6 is... Figure 5 The specific design parameters of each lens in the internal focusing camera lens are as follows: Table 6 Design values ​​of lens parameters for internal focusing cameras In Table 6, the surface numbers are assigned according to the surface sequence of each lens. Surface number 0 represents the object plane, 11 represents the aperture stop of an internal focusing camera lens, and 24 represents the image plane. The radius of curvature represents the curvature of the corresponding lens surface. A positive value indicates that the surface bends towards the image plane, and a negative value indicates that the surface bends towards the object plane. "INF" indicates that the surface is flat and the radius of curvature is infinite. D1 and D2 represent the focusing interval, and the thickness represents the central axial distance between the current surface and the next surface. The units for both the radius of curvature and the thickness are millimeters. The refractive index nd determines the ability of the material between the current surface and the next surface to deflect light. A blank space indicates that the current position is air and the refractive index is 1. The Abbe number vd determines the dispersion characteristics of the material between the current surface and the next surface.

[0046] Table 7 shows the focus interval values ​​from Table 6 (this focus interval limit ensures clear imaging at different object distances): Table 7. One design value for the focus interval of an internal focusing photographic lens. Table 8 is... Figure 5 Aspherical surface parameters in in-center focusing lenses: Table 8 Aspherical parameters of internal focusing lenses Where -1.85914472E-04 indicates that the A coefficient of face number 3 is -1.85914472 × 10 -4 .

[0047] Figure 6 This invention provides another embodiment of an internal focusing photographic lens with a transverse chromatic aberration diagram at infinity object distance. The horizontal axis of the transverse chromatic aberration diagram represents the Y-coordinate difference of different wavelengths of the principal ray on the image plane, and the vertical axis represents the field of view. The greater the deviation of the curve from the zero baseline, the more significant the chromatic aberration. Figure 6 It can be seen that the vertical chromatic aberration of the lens in this embodiment is within 11μm, and the vertical chromatic aberration is well corrected.

[0048] Figure 7 Another field curvature distortion curve of an internal focusing camera lens at infinity object distance, provided as an embodiment of this utility model. Figure 7 In the left-hand coordinate system, the horizontal coordinate represents the magnitude of the field curvature in mm; the vertical coordinate represents the normalized image height, which has no unit; where T represents the meridion and S represents the sagitta; Figure 7 As shown in the left figure, the lens provided in this embodiment effectively controls field curvature, meaning that the difference in image quality between the center and the periphery is small during imaging; in the coordinate system on the right, the horizontal axis represents the magnitude of distortion, expressed as a percentage, and the vertical axis represents the normalized image height, which has no unit; Figure 7As can be seen from the figure, the distortion of the lens provided in this embodiment has been well corrected, and the imaging distortion is small.

[0049] Figure 8 This is an axial aberration diagram of an internal focusing photographic lens at infinity, provided as an embodiment of the present invention. The horizontal axis represents the focal position, and the vertical axis represents the normalized pupil size. Each line represents a different wavelength, used to analyze the focusing differences of light of different wavelengths. The difference in focal position between different wavelengths reflects the dispersive characteristics of the optical system. If light of different wavelengths is focused at the same position, it indicates small dispersiveness; conversely, it indicates large dispersiveness. As can be seen from the figure, the focal shift variation of different wavelengths is within 70 μm, indicating small chromatic aberration in the system.

[0050] Figure 9 This is a schematic diagram of another internal docking camera lens provided in an embodiment of the present invention. Table 9 shows the structure of the lens. Figure 9 The specific parameters of the corresponding internal focusing camera lens are as follows: In this embodiment, the lens focal length is 21.61mm: Table 9 Specific parameters of internal focusing photography lenses Table 10 is... Figure 9 The specific design parameters of each lens in the internal focusing camera lens are as follows: Table 10 Design values ​​of lens parameters for internal focusing photography lenses In Table 10, the surface numbers are assigned according to the surface sequence of each lens. Surface number 0 represents the object plane, 8 and 18 represent the cemented surfaces of cemented doublet lenses, 10 represents the aperture of an internal focusing camera lens, and 22 represents the image plane. The radius of curvature represents the curvature of the corresponding lens surface. A positive value indicates that the surface bends towards the image plane, and a negative value indicates that the surface bends towards the object plane. "INF" indicates that the surface is flat and the radius of curvature is infinite. D1 and D2 represent the focusing interval, and the thickness represents the central axial distance between the current surface and the next surface. The units for the radius of curvature and the thickness are millimeters. The refractive index nd determines the ability of the material between the current surface and the next surface to deflect light. A blank space indicates that the current position is air and the refractive index is 1. The Abbe number vd determines the dispersion characteristics of the material between the current surface and the next surface.

[0051] Table 11 shows the focus interval values ​​in Table 10 (this focus interval limit ensures clear imaging at different object distances): Table 11. One design value for the focus interval of an internal focusing photographic lens. Table 12 is... Figure 9 Aspherical surface parameters in in-center focusing lenses: Table 12 Aspherical parameters of internal focusing lenses Where -5.30327246E-06 indicates that the A coefficient of face number 3 is -5.30327246 × 10 -6 .

[0052] Figure 10 This embodiment of the present invention provides a transverse chromatic aberration diagram of an internally focused photographic lens at infinity object distance. The horizontal axis of the transverse chromatic aberration diagram represents the Y-coordinate difference of the principal rays of different wavelengths on the image plane, and the vertical axis represents the field of view. The greater the deviation of the curve from the zero baseline in the figure, the more significant the chromatic aberration. As can be seen from the figure, the transverse chromatic aberration of the lens in this embodiment is within 12μm, and the transverse chromatic aberration is well corrected.

[0053] Figure 11 This invention provides another example of a field curvature distortion curve of an internally focused photographic lens at infinity object distance, as shown in this embodiment of the invention. Figure 11 In the left-hand coordinate system, the horizontal coordinate represents the magnitude of the field curvature in mm; the vertical coordinate represents the normalized image height, which has no unit; where T represents the meridion and S represents the sagitta; Figure 11 As shown in the left figure, the lens provided in this embodiment effectively controls field curvature, meaning that the difference in image quality between the center and the periphery is small during imaging; in the coordinate system on the right, the horizontal axis represents the magnitude of distortion, expressed as a percentage, and the vertical axis represents the normalized image height, which has no unit; Figure 11 As can be seen from the right figure, the distortion of the lens provided in this embodiment has been well corrected, and the imaging distortion is small.

[0054] Figure 12 This embodiment of the present invention provides an axial aberration diagram of an internally focused photographic lens at infinity object distance. The horizontal axis represents the focal position, and the vertical axis represents the normalized pupil size. Each line represents a different wavelength, used to analyze the focusing differences of different wavelengths of light. The difference in focal position between different wavelengths of light reflects the dispersive characteristics of the optical system. If different wavelengths of light are focused at the same position, it indicates small dispersiveness; conversely, it indicates large dispersiveness. Figure 12 It can be seen that the focal shift variation of different wavelengths is within 65μm, and the system has a small chromatic difference.

[0055] The specific embodiments described above do not constitute a limitation on the scope of protection of this utility model. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this utility model should be included within the scope of protection of this utility model.

Claims

1. An internal focusing photographic lens, characterized in that, It includes a first lens group with positive optical power, a second lens group with positive optical power, and a third lens group with positive or negative optical power arranged sequentially from the object side to the image side along the optical axis. The second lens group is the focusing group of the internal focusing camera lens, and the first lens group and the third lens group are the fixed groups of the internal focusing camera lens. The first lens group includes at least one meniscus lens. During the focusing process from far to near the object distance, the focusing group moves along the optical axis to the object side. The focal length of the first lens group and the focal length of the internal focusing camera lens satisfy the following: 2 <F1 / F<6.96; Wherein, F1 represents the focal length of the first lens group, and F represents the focal length of the internal focusing camera lens.

2. The internal focusing photographic lens according to claim 1, characterized in that, The focal length of the second lens group and the focal length of the internal focusing camera lens satisfy the following: 1.3 <F2 / F<2.6; Wherein, F2 represents the focal length of the second lens group, and F represents the focal length of the internal focusing camera lens.

3. The internal focusing photographic lens according to claim 1, characterized in that, The optical back focal distance and total optical length of the internal focusing camera lens satisfy the following: 0.18 <BF / TTL<0.25; Wherein, BF represents the optical back focal distance of the internal focusing camera lens, and TTL represents the total optical length of the internal focusing camera lens.

4. The internal focusing photographic lens according to claim 1, characterized in that, The maximum effective aperture and total optical length of the internal focusing camera lens satisfy the following: 0.35 <SD / TTL<0.41; Wherein, SD represents the maximum effective aperture of the internal focusing camera lens, and TTL represents the total optical length of the internal focusing camera lens.

5. The internal focusing photographic lens according to claim 1, characterized in that, The first lens group includes a first lens, a second lens, a third lens, a fourth lens, and a fifth lens arranged sequentially from the object side to the image side; the second lens group includes a sixth lens, a seventh lens, and an eighth lens arranged sequentially from the object side to the image side; and the third lens group includes a ninth lens and a tenth lens arranged sequentially from the object side to the image side.

6. The internal focusing photographic lens according to claim 5, characterized in that, The fourth and fifth lenses are used separately or combined to form a cemented lens. The sixth lens has positive optical power. The seventh lens is a meniscus lens that bends towards the image side. The eighth lens is a meniscus lens that bends towards the object side.

7. The internal focusing photographic lens according to claim 5, characterized in that, The Abbe number vd6 of the sixth lens satisfies: vd6≥53.

8. The internal focusing photographic lens according to claim 5, characterized in that, The refractive index nd4 of the fourth lens satisfies: nd4≥1.

8.

9. The internal focusing photographic lens according to claim 5, characterized in that, The second lens and the eighth lens are both plastic aspherical lenses, while the first lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens, the ninth lens, and the tenth lens are all glass spherical lenses.

10. The internal focusing photographic lens according to claim 1, characterized in that, It also includes an aperture stop, which is located between the first lens group and the second lens group.

Images