Long focal length

Abstract

The utility model discloses a long focus lens, long focus lens includes first lens, second lens, third lens, fourth lens, prism and image surface in proper order from object side to image side, wherein, first lens has positive focal power, second lens has positive focal power, third lens has negative focal power, fourth lens has positive focal power, prism has incident surface, first reflection surface, total reflection surface, second reflection surface and emergent surface, and the light of fourth lens emergent is shot into prism from incident surface, and at least reflects once through first reflection surface, total reflection surface and second reflection surface, and then emerges to image surface through emergent surface. The long focus lens of the utility model has the advantages of long focus and miniaturization, and can be used for light and thin smart mobile phone and other equipment.

Description

Technical Field

[0001] This utility model relates to the field of optical imaging technology, and in particular to a telephoto lens. Background Technology

[0002] With the rapid development of mobile communication technology and the widespread adoption of smartphones, the functions and application scenarios of mobile phone lenses are constantly being enriched and expanded. Among these, to achieve photography of distant objects, lenses need longer focal lengths. Therefore, telephoto lenses, as a functional module capable of long-distance shooting and optical zoom, have received widespread attention in the smartphone market.

[0003] However, a longer focal length means a longer optical path, resulting in a larger lens size, making it difficult to use in thin and light devices such as smartphones. Utility Model Content

[0004] In view of the above problems, the purpose of this utility model is to provide a telephoto lens with the advantages of telephoto and miniaturization, which can be used in thin and light smartphones and other devices.

[0005] This utility model provides a telephoto lens, which includes, in order from object to image, a first lens, a second lens, a third lens, a fourth lens, a prism, and an image plane; wherein, the first lens has positive optical power; the second lens has positive optical power; the third lens has negative optical power; the fourth lens has positive optical power; the prism has an incident surface, a first reflecting surface, a total reflection surface, a second reflecting surface, and an exit surface, and the light rays emitted from the fourth lens enter the prism from the incident surface, are reflected at least once by the first reflecting surface, the total reflection surface, and the second reflecting surface, and then exit the image plane through the exit surface.

[0006] Optionally, the telephoto lens further includes an aperture stop disposed on the object side of the first lens.

[0007] Optionally, the distance H10 between the fourth lens and the prism and the system focal length f of the telephoto lens satisfy the following condition: 0.02 <H 10 / f.

[0008] Optionally, the distance H from the exit surface of the prism to the image plane... 12-14 The distance between the aperture F of the telephoto lens and the aperture F of the telephoto lens satisfies: 0.3 ≤ (H 12-14 ) / F.

[0009] Optionally, the equivalent thickness H of the prism 11 The system focal length f of the telephoto lens satisfies: 0.3 <H 11 / f<1.5.

[0010] Optionally, the focal length f1 of the first lens and the system focal length f of the telephoto lens satisfy the following condition: 0.3 ≤ f1 / f ≤ 1.

[0011] Optionally, the equivalent thickness H of the prism 11 The aperture F of the telephoto lens satisfies: 3 ≤ H 11 / F≤9.

[0012] Optionally, the focal length f1 of the first lens and the focal length f2 of the second lens satisfy the condition: 0.5 ≤ f2 / f1.

[0013] Optionally, the refractive index IND1 of the first lens and the refractive index INDP of the prism satisfy the following condition: 0.56≤IND1 / INDP≤1.3.

[0014] Optionally, the refractive index INDP of the prism and the aperture F of the telephoto lens satisfy the following condition: 0.45≤INDP / F≤1.15.

[0015] Optionally, the imaging circle diameter MIC of the telephoto lens and the system focal length f of the telephoto lens satisfy the following condition: 0.33≤MIC / f≤1.

[0016] Optionally, the distance H from the object vertex of the first lens to the prism 2-10 The equivalent thickness H of the prism 11 The following condition must be met: 0.21 ≤ (H) 2-10 ) / H 11 ≤0.55.

[0017] The telephoto lens provided by this utility model includes, in order from object to image, a first lens, a second lens, a third lens, a fourth lens, a prism, and an image plane. The first lens has positive optical power; the second lens has positive optical power; the third lens has negative optical power; and the fourth lens has positive optical power. The prism has an incident surface, a first reflecting surface, a total reflection surface, a second reflecting surface, and an exit surface. The light rays emitted from the fourth lens enter the prism from the incident surface, are reflected at least once by the first reflecting surface, the total reflection surface, and the second reflecting surface, and then exit the image plane through the exit surface. The optical power of the first to fourth lenses follows a positive-positive-negative-positive arrangement. The first lens has positive optical power and can act as a light-gathering lens. The second to fourth lenses can correct aberrations. Using fewer lenses reduces the overall height. Furthermore, the back focal length is folded multiple times inside the prism, shortening the back focal length of the lens and reducing its height. Through the reasonable allocation of the optical power, spacing, and refractive index of each lens, as well as the configuration of the prism, the telephoto lens has the advantages of long focal length and miniaturization, making it suitable for thin and light smartphones and other devices. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of this utility model, the drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this utility model and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 A schematic diagram of the prism equivalent unfolding structure of a telephoto lens according to an embodiment of this application is shown.

[0020] Figure 2 It shows Figure 1 A schematic diagram of the structure of a telephoto lens according to one embodiment.

[0021] Figure 3 A schematic diagram of the prism equivalent unfolding structure of a telephoto lens according to Embodiment 1 of this application is shown.

[0022] Figures 4 to 6 The MTF curve, relative illumination and Y field of view diagram, and distortion diagram of the telephoto lens of Example 1 are shown respectively.

[0023] Figure 7 A schematic diagram of the prism equivalent unfolding structure of a telephoto lens according to Embodiment 2 of this application is shown.

[0024] Figures 8 to 10 The MTF curve, relative illumination and Y field of view diagram, and distortion diagram of the telephoto lens of Example 2 are shown respectively.

[0025] Figure 11 A schematic diagram of the prism equivalent unfolding structure of a telephoto lens according to Embodiment 3 of this application is shown.

[0026] Figures 12 to 14 The MTF curve, relative illumination and Y field of view diagram, and distortion diagram of the telephoto lens of Example 3 are shown respectively. Detailed Implementation

[0027] The foregoing and other technical contents, features, and effects of this utility model will be clearly presented in the following detailed description of the preferred embodiments with reference to the accompanying drawings. Through the description of the specific embodiments, a more in-depth and specific understanding can be gained of the technical means and effects adopted by this utility model to achieve its intended purpose. However, the accompanying drawings are for reference and illustration only and are not intended to limit this utility model; some well-known parts may not be shown. In the various drawings, the same elements are represented by similar reference numerals. For clarity, the various parts in the drawings are not necessarily drawn strictly to scale.

[0028] It is important to understand that the terms “first,” “second,” “third,” and “fourth,” etc., are used merely to distinguish elements or circuits with similar properties, and do not indicate or imply relative importance or a specific order. The terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, which includes not only the listed elements but also other elements not expressly listed.

[0029] In the accompanying drawings, the thickness, size, and shape of the lenses have been slightly exaggerated for ease of illustration. Specifically, the shape of the sphere shown in the drawings is illustrated by way of example. That is, the shape of the sphere is not limited to that shown in the drawings. The drawings are for illustrative purposes only and are not drawn strictly to scale.

[0030] In this article, the paraxial region refers to the region near the optical axis. If the lens surface is convex and the location of the convexity is not defined, it means that the lens surface is convex at least in the paraxial region; if the lens surface is concave and the location of the concaveness is not defined, it means that the lens surface is concave at least in the paraxial region. The surface of each lens closest to the subject is called the object plane of the lens, and the surface of each lens closest to the image plane is called the image plane of the lens.

[0031] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0032] The features, principles and other aspects of this application are described in detail below.

[0033] like Figure 1 and Figure 2 As shown, the telephoto lens according to an exemplary embodiment of this application includes, in order from object to image, a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a prism P, and an image plane IMG; wherein, the first lens L1 has positive optical power; the second lens L2 has positive optical power; the third lens L3 has negative optical power; the fourth lens L4 has positive optical power; and the prism P has an incident surface, a first reflecting surface, a total reflection surface, a second reflecting surface, and an exit surface (…). Figure 1 Not shown, please refer to Figure 2 The light rays emitted from the fourth lens L4 enter the prism P from the incident surface, are reflected at least once by the first reflecting surface, the total reflection surface, and the second reflecting surface, and then exit the image plane IMG through the exit surface.

[0034] Specifically, the optical powers of the first lens L1 to the fourth lens L4 follow a positive-positive-negative-positive arrangement. The first lens L1 has a positive optical power and acts as a light-gathering element, while the second lens L2 to the fourth lens L4 correct aberrations. The light rays exiting the fourth lens L4 enter the prism P from the incident surface, undergo at least one reflection via the first reflecting surface, the total internal reflection surface, and the second reflecting surface, and then exit through the exit surface to the image plane IMG. This folds the back focal length within the prism P, shortening the lens's back focal length and reducing its height. Through the rational allocation of the optical powers, spacing, and refractive indices of each lens, and the configuration of the prism P, the telephoto lens achieves the advantages of both long focal length and miniaturization, making it suitable for use in thin and light devices such as smartphones.

[0035] In an exemplary embodiment, the lenses in the lens assembly of the telephoto lens according to this application can be set aspherical. For example, the first lens L1, the second lens L2, the third lens L3 and the fourth lens L4 are all aspherical. Aspherical lenses can better correct spherical aberration, reduce chromatic aberration and improve light transmittance, and can more accurately control the focusing and distribution of light, thereby improving image quality.

[0036] In one exemplary embodiment, the telephoto lens according to this application has a first lens L1 that is biconvex, a second lens L2 that is biconvex, a third lens L3 that is biconcave, and a fourth lens L4 that is biconvex.

[0037] In an exemplary embodiment, the telephoto lens according to this application further includes an aperture stop STO, which can be disposed on the object side of the first lens L1. Thus, the amount of light entering the optical system can be controlled by the aperture stop STO, and the incident beam angle can be limited, which helps to optimize image quality. Furthermore, the aperture stop STO can optimize incident beam control, and a large aperture can achieve a large aperture for the system. At a large aperture, for example, less than f / 2.2, it can meet the requirements for use of a telephoto lens in low-light environments such as at night. In other exemplary embodiments, the aperture stop STO can be disposed between adjacent lenses.

[0038] In an exemplary embodiment, the telephoto lens according to this application can satisfy 0.02. <H 10 / f; where the distance between the fourth lens L4 and the prism P is H10, and the system focal length of the telephoto lens is f. Satisfying 0.02 <H 10 / f, by controlling the ratio of the distance H10 between the fourth lens L4 and the prism P to the system focal length f of the telephoto lens, helps to avoid collisions between the lens and the prism P after the assembly module.

[0039] In an exemplary embodiment, the telephoto lens according to this application can satisfy 0.3≤(H 12-14 ) / F; where H is the distance H from the exit surface of prism P to the image plane IMG. 12-14The aperture F of the telephoto lens satisfies 0.3 ≤ (H) 12-14 ) / F, by controlling the distance H from the exit surface of prism P to the image plane IMG. 12-14 The ratio of the aperture F of a telephoto lens to the aperture of a telephoto lens helps to control the impact of dirt on the image.

[0040] In an exemplary embodiment, the telephoto lens according to this application can satisfy 0.3. <H 11 / f<1.5; where the equivalent thickness of prism P is H. 11 The system focal length of the telephoto lens is f. It satisfies 0.3. <H 11 / f<1.5, by controlling the equivalent thickness H of prism P. 11 The ratio of the system focal length f to that of a telephoto lens can prevent the prism P from being too long, which is beneficial for controlling the system volume within a certain range.

[0041] In an exemplary embodiment, the telephoto lens according to this application satisfies 0.3≤f1 / f≤1; wherein the focal length of the first lens L1 is f1, and the system focal length of the telephoto lens is f. Satisfying 0.3≤f1 / f≤1, by controlling the ratio of the focal length f1 of the first lens L1 to the system focal length f of the telephoto lens, is beneficial for correcting spherical aberration and increasing the aperture of the system.

[0042] In an exemplary embodiment, the telephoto lens according to this application can satisfy 3≤H 11 / F≤9; where the equivalent thickness of prism P is H. 11 The aperture of the telephoto lens is F. It satisfies 3 ≤ H. 11 / F≤9, by controlling the equivalent thickness H of prism P. 11 The ratio of the aperture F of the telephoto lens to the aperture of the telephoto lens is beneficial for increasing the system's aperture.

[0043] In an exemplary embodiment, the telephoto lens according to this application satisfies 0.5 ≤ f2 / f1; wherein the focal length of the first lens L1 is f1 and the focal length of the second lens L2 is f2. Satisfying 0.5 ≤ f2 / f1, by controlling the ratio of the focal length f1 of the first lens L1 to the focal length f2 of the second lens L2, helps to control system spherical aberration and improve image quality.

[0044] In an exemplary embodiment, the telephoto lens according to this application satisfies 0.56≤IND1 / INDP≤1.3; wherein the refractive index of the first lens L1 is IND1, and the refractive index of the prism P is INDP. Satisfying 0.56≤IND1 / INDP≤1.3, by controlling the ratio of the refractive index IND1 of the first lens L1 to the refractive index INDP of the prism P, is beneficial for correcting chromatic aberration in the system and improving image quality.

[0045] In an exemplary embodiment, the telephoto lens according to this application satisfies 0.45≤INDP / F≤1.15; wherein the refractive index of prism P is INDP, and the aperture of the telephoto lens is F. Satisfying 0.45≤INDP / F≤1.15, by controlling the ratio of the refractive index INDP of prism P to the aperture F of the telephoto lens, helps to control the focal length of the system to meet the requirements.

[0046] In an exemplary embodiment, the telephoto lens according to this application satisfies 0.33≤MIC / f≤1; wherein, the imaging circle diameter of the telephoto lens is MIC, and the system focal length of the telephoto lens is f. Satisfying 0.33≤MIC / f≤1, by controlling the ratio of the imaging circle diameter MIC of the telephoto lens to the system focal length f of the telephoto lens, is beneficial to control the system focal length to meet the requirements.

[0047] In an exemplary embodiment, the telephoto lens according to this application can satisfy 0.21≤(H 2-10 ) / H 11 ≤0.55; where the distance from the object vertex of the first lens L1 to the prism P is H. 2-10 The equivalent thickness of prism P is H. 11 Satisfying 0.21≤(H) 2-10 ) / H 11 ≤0.55, by controlling the distance H from the object vertex of the first lens L1 to the prism P. 2-10 Equivalent thickness H of prism P 11 The ratio of [value] is beneficial for controlling the system length, reasonably reducing the overall thickness of the lens assembly, and realizing lens miniaturization.

[0048] In an exemplary embodiment, the telephoto lens according to this application further includes a color filter IR for correcting color aberrations and / or a protective glass for protecting the photosensitive element located on the image plane IMG. In one exemplary embodiment, the color filter IR and / or the protective glass may be disposed between the image plane IMG and the exit surface of the prism P.

[0049] Based on the same inventive concept, the electronic device according to the exemplary embodiments of this application includes the telephoto lens described above. The electronic device is, but is not limited to, smartphones, tablets, laptops, gimbal cameras, surveillance cameras, and other imaging devices. Implementations of this electronic device can refer to embodiments of the telephoto lens; repeated details will not be elaborated further.

[0050] However, those skilled in the art will understand that the number of lenses constituting the optical imaging lens can be varied to obtain the various results and advantages described herein without departing from the technical solutions claimed in this application. For example, although four lenses are described as an example in the embodiments, the optical imaging lens is not limited to including four lenses. If desired, the optical imaging lens may also include other numbers of lenses.

[0051] The following describes in further detail, with reference to the accompanying drawings, specific embodiments of the telephoto lens applicable to the above-described embodiments.

[0052] Example 1

[0053] The following is for reference Figure 3 A telephoto lens according to Embodiment 1 of this application is described. Figure 3 A schematic diagram of the prism equivalent unfolding structure of a telephoto lens according to Embodiment 1 of this application is shown.

[0054] like Figure 3 As shown, the telephoto lens, from object side to image side, includes a first lens L1, an aperture stop STO, a second lens L2, a third lens L3, a fourth lens L4, a prism P, a filter IR, and an image plane IMG. Each of the first lens L1 to the fourth lens L4 includes an object-side surface facing the object side and allowing imaging light to pass through, and an image-side surface facing the image side and allowing imaging light to pass through. The aperture stop STO can be positioned on the object-side surface of the first lens L1. The filter IR can be positioned between the image plane IMG and the exit surface of the prism P.

[0055] Please refer to the following as well. Figure 3 As per Table 1, the first lens L1 has positive optical power, with both its object and image surfaces being convex. The second lens L2 has positive optical power, with both its object and image surfaces being convex. The third lens L3 has negative optical power, with both its object and image surfaces being concave. The fourth lens L4 has positive optical power, with both its object and image surfaces being convex. The incident surface of prism P is positioned opposite to that of the fourth lens L4, and the exit surface of prism P can be positioned opposite to the object surface of filter IR. Filter IR has both an object surface and an image surface. Light rays can pass sequentially through aperture STO, the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, prism P, and filter IR, and finally form an image on the image plane IMG.

[0056] Table 1 shows the basic parameters of the telephoto lens of Example 1, where the units for radius of curvature, thickness, and optical power are millimeters (mm).

[0057] Table 1:

[0058]

[0059] Wherein, L1-R1 represents the object aspect of the first lens L1, L1-R2 represents the image aspect of the first lens L1, L2-R1 represents the object aspect of the second lens L2, L2-R2 represents the image aspect of the second lens L2, L3-R1 represents the object aspect of the third lens L3, L3-R2 represents the image aspect of the third lens L3, L4-R1 represents the object aspect of the fourth lens L4, L4-R2 represents the image aspect of the fourth lens L4, IR-R1 represents the object aspect of the filter IR, and IR-R2 represents the image aspect of the filter IR.

[0060] In Embodiment 1, the object and image aspects of the first lens L1 to the fourth lens L4 can both be extended aspherical surfaces, and the surface shape of each extended aspherical surface can be defined using, but is not limited to, the following aspherical formula:

[0061] (1)

[0062] Where x is the distance vector from the vertex of the extended aspherical surface at a height h along the optical axis; c is the paraxial curvature of the extended aspherical surface, c = 1 / R (i.e., the paraxial curvature c is the reciprocal of the radius of curvature in Table 1 above); k is the conic coefficient; Ai is the i-th order correction coefficient of the extended aspherical surface. Table 2 shows the higher-order coefficients A4, A6, A8, A10, A12, A14, A16, A18, A20, and A22 of the extended aspherical mirror surface that can be used for the object and image aspects of the first lens L1 to the fourth lens L4 in Embodiment 1.

[0063] Table 2:

[0064]

[0065]

[0066] In this embodiment, based on the reasonable allocation of optical power distribution, spacing, and refractive index of the first lens L1 to the fourth lens L4 in the table above, and the back focal ray folding under the equivalent thickness of prism P, a telephoto lens with both long focal length and miniaturization can be achieved. Specifically, the telephoto lens has a focal length f of 13mm, a working wavelength of 430-650nm, an aperture of F2.2, an imaging circle diameter of 7.8mm, and a field of view of 33.2°. The relationship between the distance H10 between the fourth lens L4 and prism P and the system focal length f of the telephoto lens is H... 10 / f = 0.037, which satisfies: 0.02 <H 10 / f. The distance H from the exit surface of prism P to the image plane IMG. 12-14 The relationship between H and the aperture F of a telephoto lens is (H) 12-14 ) / F=0.414, satisfying: 0.3≤(H) 12-14 The equivalent thickness H of prism P is ) / F.11 The relationship between H and the system focal length f of the telephoto lens is... 11 / f=1.073, which satisfies: 0.3 <H 11 / f<1.5. The relationship between the focal length f1 of the first lens L1 and the system focal length f of the telephoto lens is f1 / f=0.554, satisfying: 0.3≤f1 / f≤1. The equivalent thickness H of the prism P. 11 The relationship between H and the aperture F of a telephoto lens is... 11 / F=6.341, satisfying: 3≤H 11 / F≤9. The relationship between the focal length f1 of the first lens L1 and the focal length f2 of the second lens L2 is f2 / f1=1.153, satisfying: 0.5≤f2 / f1. The relationship between the refractive index IND1 of the first lens L1 and the refractive index INDP of the prism P is IND1 / INDP=0.910, satisfying: 0.56≤IND1 / INDP≤1.3. The relationship between the refractive index INDP of the prism P and the aperture F of the telephoto lens is INDP / F=0.805, satisfying: 0.45≤INDP / F≤1.15. The relationship between the imaging circle diameter MIC of the telephoto lens and the system focal length f of the telephoto lens is MIC / f=0.600, satisfying: 0.33≤MIC / f≤1. The distance H from the object vertex of the first lens L1 to the prism P. 2-10 Equivalent thickness H of prism P 11 The relationship between them is (H) 2-10 ) / H 11 =0.352, satisfying: 0.21≤(H 2-10 ) / H 11 ≤0.55.

[0067] Figure 4 The MTF curve of the telephoto lens in Example 1 is shown. The MTF (Modulation Transfer Function) curve shows the transmission of image details (i.e. image contrast) at different spatial frequencies by the imaging system. At a spatial frequency of 89 lp / mm, the OTF modulus is greater than 0.5, which meets the resolution requirements. Figure 5 The relative illumination and Y-field diagram of the telephoto lens of Example 1 are shown. The relative illumination is greater than 50%, and the image illumination is uniform. Figure 6 The distortion diagram of the telephoto lens in Example 1 is shown; the distortion is less than 1%, indicating good correction. According to... Figures 4 to 6 As can be seen, the telephoto lens given in Example 1 has excellent resolution, uniform image illumination, and good correction, and can achieve good image quality.

[0068] Example 2

[0069] The following is for reference Figure 7 Describes a telephoto lens according to Embodiment 2 of this application. Figure 7 A schematic diagram of the prism equivalent unfolding structure of a telephoto lens according to Embodiment 2 of this application is shown.

[0070] like Figure 7 As shown, the telephoto lens, from object side to image side, includes a first lens L1, an aperture stop STO, a second lens L2, a third lens L3, a fourth lens L4, a prism P, a filter IR, and an image plane IMG. Each of the first lens L1 to the fourth lens L4 includes an object-side surface facing the object side and allowing imaging light to pass through, and an image-side surface facing the image side and allowing imaging light to pass through. The aperture stop STO can be positioned on the object-side surface of the first lens L1. The filter IR can be positioned between the image plane IMG and the exit surface of the prism P.

[0071] Please refer to the following as well. Figure 7 As per Table 3, the first lens L1 has positive optical power, with both its object and image surfaces being convex. The second lens L2 has positive optical power, with both its object and image surfaces being convex. The third lens L3 has negative optical power, with both its object and image surfaces being concave. The fourth lens L4 has positive optical power, with both its object and image surfaces being convex. The incident surface of prism P is positioned opposite to that of the fourth lens L4, and the exit surface of prism P can be positioned opposite to the object surface of filter IR. Filter IR has both an object surface and an image surface. Light rays can pass sequentially through aperture STO, the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, prism P, and filter IR, and finally form an image on the image plane IMG.

[0072] Table 3 shows the basic parameters of the telephoto lens in Example 2, where the units for radius of curvature, thickness, and optical power are millimeters (mm).

[0073] Table 3:

[0074]

[0075] Table 4 shows the higher-order coefficients A4, A6, A8, A10, A12, A14, A16, A18, A20, and A22 of the extended aspherical mirrors that can be used for the object and image aspects of the first lens L1 to the fourth lens L4 in Embodiment 2.

[0076] Table 4:

[0077]

[0078]

[0079] In this embodiment, based on the reasonable allocation of optical power distribution, spacing, and refractive index of the first lens L1 to the fourth lens L4 in the table above, and the back focal ray folding under the equivalent thickness of prism P, a telephoto lens with both long focal length and miniaturization can be achieved. Specifically, the telephoto lens has a focal length f of 13mm, a working wavelength of 430-650nm, an aperture of F2.2, an imaging circle diameter of 7.8mm, and a field of view of 33.2°. The relationship between the distance H10 between the fourth lens L4 and prism P and the system focal length f of the telephoto lens is H... 10 / f = 0.037, which satisfies: 0.02 <H 10 / f. The distance H from the exit surface of prism P to the image plane IMG. 12-14 The relationship between H and the aperture F of a telephoto lens is (H) 12-14 ) / F=0.414, satisfying: 0.3≤(H) 12-14 The equivalent thickness H of prism P is ) / F. 11 The relationship between H and the system focal length f of the telephoto lens is... 11 / f=1.073, which satisfies: 0.3 <H 11 / f<1.5. The relationship between the focal length f1 of the first lens L1 and the system focal length f of the telephoto lens is f1 / f=0.579, satisfying: 0.3≤f1 / f≤1. The equivalent thickness H of prism P. 11 The relationship between H and the aperture F of a telephoto lens is... 11 / F=6.341, satisfying: 3≤H 11 / F≤9. The relationship between the focal length f1 of the first lens L1 and the focal length f2 of the second lens L2 is f2 / f1=1.096, satisfying: 0.5≤f2 / f1. The relationship between the refractive index IND1 of the first lens L1 and the refractive index INDP of the prism P is IND1 / INDP=0.910, satisfying: 0.56≤IND1 / INDP≤1.3. The relationship between the refractive index INDP of the prism P and the aperture F of the telephoto lens is INDP / F=0.805, satisfying: 0.45≤INDP / F≤1.15. The relationship between the imaging circle diameter MIC of the telephoto lens and the system focal length f of the telephoto lens is MIC / f=0.600, satisfying: 0.33≤MIC / f≤1. The distance H from the object vertex of the first lens L1 to the prism P. 2-10 Equivalent thickness H of prism P 11 The relationship between them is (H) 2-10 ) / H 11 =0.356, satisfying: 0.21≤(H 2-10 ) / H 11 ≤0.55.

[0080] Figure 8The MTF curve of the telephoto lens in Example 2 is shown. The MTF (Modulation Transfer Function) curve shows the transmission of image details (i.e. image contrast) at different spatial frequencies by the imaging system. At a spatial frequency of 89 lp / mm, the OTF modulus is greater than 0.5, which meets the resolution requirements. Figure 9 The relative illumination and Y-field diagram of the telephoto lens in Example 2 are shown. The relative illumination is greater than 50%, and the image illumination is uniform. Figure 10 The distortion diagram of the telephoto lens in Example 2 is shown; the distortion is less than 1%, indicating good correction. According to... Figures 8 to 10 As can be seen, the telephoto lens given in Example 2 has excellent resolution, uniform image illumination, and good correction, and can achieve good image quality.

[0081] Example 3

[0082] The following is for reference Figure 11 Description of a telephoto lens according to Embodiment 3 of this application. Figure 11 A schematic diagram of the prism equivalent unfolding structure of a telephoto lens according to Embodiment 3 of this application is shown.

[0083] like Figure 11 As shown, the telephoto lens, from object side to image side, includes a first lens L1, an aperture stop STO, a second lens L2, a third lens L3, a fourth lens L4, a prism P, a filter IR, and an image plane IMG. Each of the first lens L1 to the fourth lens L4 includes an object-side surface facing the object side and allowing imaging light to pass through, and an image-side surface facing the image side and allowing imaging light to pass through. The aperture stop STO can be positioned on the object-side surface of the first lens L1. The filter IR can be positioned between the image plane IMG and the exit surface of the prism P.

[0084] Please refer to the following as well. Figure 11 As per Table 5, the first lens L1 has positive optical power, with both its object and image surfaces being convex. The second lens L2 has positive optical power, with both its object and image surfaces being convex. The third lens L3 has negative optical power, with both its object and image surfaces being concave. The fourth lens L4 has positive optical power, with both its object and image surfaces being convex. The incident surface of prism P is positioned opposite to the fourth lens L4, and the exit surface of prism P can be positioned opposite to the object surface of filter IR. Filter IR has both an object surface and an image surface. Light rays can pass sequentially through aperture STO, the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, prism P, and filter IR, and finally form an image on the image plane IMG.

[0085] Table 5 shows the basic parameters of the telephoto lens in Example 3, where the units for radius of curvature, thickness, and optical power are all millimeters (mm).

[0086] Table 5:

[0087]

[0088] Table 6 shows the higher-order coefficients A4, A6, A8, A10, A12, A14, A16, A18, A20, and A22 of the extended aspherical mirrors that can be used for the object and image aspects of the first lens L1 to the fourth lens L4 in Embodiment 3.

[0089] Table 6:

[0090]

[0091]

[0092] In this embodiment, based on the reasonable allocation of optical power distribution, spacing, and refractive index of the first lens L1 to the fourth lens L4 in the table above, and the back focal ray folding under the equivalent thickness of prism P, a telephoto lens with both long focal length and miniaturization can be achieved. Specifically, the telephoto lens has a focal length f of 14.66mm, a working wavelength of 470-650nm, an aperture of F2.4, an imaging circle diameter of 7.88mm, and a field of view of 30.2°. The relationship between the distance H10 between the fourth lens L4 and prism P and the system focal length f of the telephoto lens is H... 10 / f = 0.033, which satisfies: 0.02 <H 10 / f. The distance H from the exit surface of prism P to the image plane IMG. 12-14 The relationship between H and the aperture F of a telephoto lens is (H) 12-14 ) / F=0.379, satisfying: 0.3≤(H) 12-14 The equivalent thickness H of prism P is ) / F. 11 The relationship between H and the system focal length f of the telephoto lens is... 11 / f=1.037, which satisfies: 0.3 <H 11 / f<1.5. The relationship between the focal length f1 of the first lens L1 and the system focal length f of the telephoto lens is f1 / f=0.600, satisfying: 0.3≤f1 / f≤1. The equivalent thickness H of the prism P. 11 The relationship between H and the aperture F of a telephoto lens is... 11 / F=6.334, satisfying: 3≤H 11 / F≤9. The relationship between the focal length f1 of the first lens L1 and the focal length f2 of the second lens L2 is f2 / f1=0.924, satisfying: 0.5≤f2 / f1. The relationship between the refractive index IND1 of the first lens L1 and the refractive index INDP of the prism P is IND1 / INDP=0.893, satisfying: 0.56≤IND1 / INDP≤1.3. The relationship between the refractive index INDP of the prism P and the aperture F of the telephoto lens is INDP / F=0.738, satisfying: 0.45≤INDP / F≤1.15. The relationship between the imaging circle diameter MIC of the telephoto lens and the system focal length f of the telephoto lens is MIC / f=0.532, satisfying: 0.33≤MIC / f≤1. The distance H from the object vertex of the first lens L1 to the prism P. 2-10 Equivalent thickness H of prism P 11 The relationship between them is (H) 2-10 ) / H 11 =0.328, satisfying: 0.21≤(H 2-10 ) / H 11 ≤0.55.

[0093] Figure 12 The MTF curve of the telephoto lens in Example 3 is shown. The MTF (Modulation Transfer Function) curve shows the transmission of image details (i.e., image contrast) at different spatial frequencies by the imaging system. At a spatial frequency of 89 lp / mm, the OTF modulus is greater than 0.5, which meets the resolution requirements. Figure 13 The relative illumination and Y-field diagram of the telephoto lens in Example 3 are shown. The relative illumination is greater than 50%, and the image illumination is uniform. Figure 14 The distortion diagram of the telephoto lens in Example 3 is shown; the distortion is less than 1%, indicating good correction. According to... Figures 12 to 14 As can be seen, the telephoto lens given in Example 3 has excellent resolution, uniform image illumination, and good correction, and can achieve good image quality.

[0094] In summary, Examples 1, 2, and 3 satisfy the relationships shown in Table 7.

[0095] Table 7:

[0096]

[0097] The above description is merely a preferred embodiment of this application and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the utility model involved in this application is not limited to the technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the inventive concept. For example, technical solutions formed by substituting the above features with (but not limited to) technical features with similar functions disclosed in this application.

Claims

1. A telephoto lens, characterized in that, The sequence from object to image includes the first lens, second lens, third lens, fourth lens, prism, and image plane; among which, The first lens has positive optical power; the second lens has positive optical power; the third lens has negative optical power; and the fourth lens has positive optical power. The prism has an incident surface, a first reflecting surface, a total reflection surface, a second reflecting surface, and an exit surface. The light rays emitted from the fourth lens enter the prism from the incident surface, are reflected at least once by the first reflecting surface, the total reflection surface, and the second reflecting surface, and then exit to the image plane through the exit surface.

2. The telephoto lens according to claim 1, characterized in that, The telephoto lens also includes an aperture stop, which is disposed on the object side of the first lens.

3. The telephoto lens according to claim 1, characterized in that, The distance H10 between the fourth lens and the prism satisfies the following condition with respect to the system focal length f of the telephoto lens: 0.

02. <H10 / f。 4. The telephoto lens according to claim 1, characterized in that, The focal length f1 of the first lens and the system focal length f of the telephoto lens satisfy the following condition: 0.3 ≤ f1 / f ≤ 1.

5. The telephoto lens according to claim 1, characterized in that, The equivalent thickness H11 of the prism and the aperture F of the telephoto lens satisfy the following condition: 3≤H11 / F≤9.

6. The telephoto lens according to claim 1, characterized in that, The focal length f1 of the first lens and the focal length f2 of the second lens satisfy the condition: 0.5 ≤ f2 / f1.

7. The telephoto lens according to claim 1, characterized in that, The refractive index IND1 of the first lens and the refractive index INDP of the prism satisfy the following condition: 0.56≤IND1 / INDP≤1.

3.

8. The telephoto lens according to claim 1, characterized in that, The refractive index INDP of the prism and the aperture F of the telephoto lens satisfy the following condition: 0.45≤INDP / F≤1.

15.

9. The telephoto lens according to claim 1, characterized in that, The imaging circle diameter MIC of the telephoto lens and the system focal length f of the telephoto lens satisfy the following condition: 0.33≤MIC / f≤1.

10. The telephoto lens according to claim 1, characterized in that, The distance H2-10 from the object vertex of the first lens to the prism and the equivalent thickness H11 of the prism satisfy the following condition: 0.21≤(H2-10) / H11≤0.55.

Images