Telephoto lenses and electronic devices

Abstract

This invention discloses a telephoto lens and electronic device, comprising a lens assembly, a reflecting prism, and a compensating prism from the object side to the image side. The lens assembly includes multiple lenses arranged in sequence. The reflecting prism includes a first working surface, a second working surface, and a third working surface. Light emitted from the lens assembly enters the reflecting prism from the first working surface, undergoes a first reflection from the second working surface back to the first working surface, undergoes a second reflection from the first working surface back to the third working surface, and exits from the third working surface. The compensating prism includes a fourth working surface and a fifth working surface. Light emitted from the reflecting prism enters the compensating prism from the fourth working surface and exits from the fifth working surface, so that the zero-field-of-view principal ray is perpendicularly incident on the imaging surface of the imaging chip, which is vertically arranged inside the lens module. The telephoto lens and electronic device of this invention can reduce the height of the telephoto lens, achieving lens miniaturization.

Description

Technical Field

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

[0002] With the increasing multifunctionality of various electronic products, camera functionality has become an essential feature for many electronic products, such as smartphones and tablets with camera capabilities.

[0003] However, as users have higher and higher requirements for lenses, telephoto lenses with long back focal lengths generally have the problem of being too tall and protruding from the camera body, resulting in an unsightly appearance. Summary of the Invention

[0004] In view of the above problems, the purpose of this invention is to provide a telephoto lens and an electronic device that can reduce the height of the telephoto lens and achieve lens miniaturization.

[0005] This invention provides a telephoto lens, which includes a lens assembly, a reflecting prism, and a compensating prism from the object side to the image side. The lens assembly includes a plurality of lenses arranged in sequence. The reflecting prism includes a first working surface, a second working surface, and a third working surface. Light emitted from the lens assembly enters the reflecting prism from the first working surface, undergoes a first reflection from the second working surface back to the first working surface, undergoes a second reflection from the first working surface back to the third working surface, and exits from the third working surface. The compensating prism includes a fourth working surface and a fifth working surface. Light emitted from the reflecting prism enters the compensating prism from the fourth working surface and exits from the fifth working surface, so that the zero-field principal ray is perpendicularly incident on the imaging surface of the imaging chip, which is vertically arranged inside the lens module.

[0006] Optionally, the compensation prism is a wedge prism, and the fourth working surface and the fifth working surface form a wedge angle.

[0007] Optionally, the reflecting prism is a trapezoidal prism.

[0008] Optionally, the fourth working surface of the compensation prism coincides with the third working surface of the reflection prism.

[0009] Optionally, the compensating prism and the reflecting prism form a combined prism.

[0010] Optionally, the Abbe coefficient Ab5 of the reflecting prism and the Abbe coefficient Ab6 of the compensating prism satisfy: Ab5>40, Ab6>40.

[0011] Optionally, the refractive index N5 of the reflecting prism and the refractive index N6 of the compensating prism satisfy: 0.1 <ABS(N5-N6)。

[0012] Optionally, the distance M1 from the lens surface of the lens assembly to the first working surface, and the distance M2 from the first working surface to the lower end point of the imaging surface, satisfy: M1 < 5.1 mm, M2 < 5 mm, 0.5 <M1 / ML2<1.5。

[0013] Optionally, the focal length f' and the imaging circle diameter ImC of the telephoto lens satisfy: 1 <f’ / ImC<2.2。

[0014] Optionally, the angle α1 between the first working surface and the second working surface satisfies: 25°≤α1≤45°.

[0015] Optionally, the angle α2 between the fourth working surface and the fifth working surface satisfies: 8°≤α2≤25°.

[0016] Optionally, the lens assembly includes a first lens, a second lens, a third lens, and a fourth lens, wherein the first lens has positive optical power and the second lens has negative optical power.

[0017] Optionally, the focal length f1 of the first lens and the focal length f2 of the second lens satisfy: 1≤|f2 / f1|≤2.

[0018] The present invention also provides an electronic device including the telephoto lens described above.

[0019] The telephoto lens and electronic device provided by this invention include a lens assembly, a folding prism, and a compensating prism from the object side to the image side. By rationally allocating the optical power, spacing, and refractive index of each lens in the lens assembly, as well as the folding of the back focal path of the lens by the folding prism, and the correction and deflection of the light by the compensating prism, a telephoto lens with a large aperture and a large target surface can be provided. The height of the telephoto lens can be reduced by using the folding prism, and the imaging chip can be set vertically by using the compensating prism, which facilitates the installation of the imaging chip. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention 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.

[0021] Figure 1 A schematic diagram of the structure of a telephoto lens according to an embodiment of this application is shown.

[0022] Figure 2 A schematic diagram of the structure of a telephoto lens according to Embodiment 1 of this application is shown.

[0023] Figures 3 to 5 The axial aberration diagram, distortion diagram, and MTF curve of the telephoto lens of Example 1 are shown respectively.

[0024] Figure 6 A schematic diagram of the structure of a telephoto lens according to Embodiment 2 of this application is shown.

[0025] Figures 7 to 9 The axial aberration diagram, distortion diagram, and MTF curve of the telephoto lens of Example 2 are shown respectively.

[0026] Figure 10 A schematic diagram of the structure of a telephoto lens according to Embodiment 3 of this application is shown.

[0027] Figures 11 to 13 The axial aberration diagram, distortion diagram, and MTF curve of the telephoto lens of Example 3 are shown respectively. Detailed Implementation

[0028] The foregoing and other technical contents, features, and effects of the present invention will be clearly presented in the following detailed description of 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 the present invention to achieve its intended purpose. However, the accompanying drawings are for reference and illustration only and are not intended to limit the present invention; 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.

[0029] It is important to understand that the terms "first," "second," "third," "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.

[0030] In the accompanying drawings, the thickness, size, and shape of the lenses have been slightly exaggerated for ease of illustration. Specifically, the shapes of the spherical or aspherical surfaces shown in the drawings are illustrated by way of example. That is, the shapes of the spherical or aspherical surfaces are not limited to those shown in the drawings. The drawings are for illustrative purposes only and are not strictly to scale.

[0031] 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-side surface of the lens, and the surface of each lens closest to the imaging plane (IMG) is called the image-side surface of the lens.

[0032] 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.

[0033] The features, principles and other aspects of this application are described in detail below.

[0034] Figure 1 A schematic diagram of the structure of a telephoto lens according to an embodiment of this application is shown.

[0035] According to an exemplary embodiment of this application, a telephoto lens includes a lens assembly, a reflecting prism P1, and a compensating prism P2 from the object side to the image side. The lens assembly includes a plurality of lenses arranged in sequence. The reflecting prism P1 includes a first working surface, a second working surface, and a third working surface. Light emitted from the lens assembly enters the reflecting prism P1 from the first working surface, undergoes a first reflection from the second working surface back to the first working surface, undergoes a second reflection from the first working surface back to the third working surface, and exits from the third working surface. The compensating prism P2 includes a fourth working surface and a fifth working surface. Light emitted from the reflecting prism P1 enters the compensating prism P2 from the fourth working surface and exits from the fifth working surface, so that the zero-field principal ray is perpendicularly incident on the imaging surface IMG of the imaging chip, wherein the imaging chip is vertically arranged inside the lens module.

[0036] Specifically, the lens assembly receives object-side light and achieves telephoto imaging by rationally allocating the optical power, spacing, and refractive index of the multiple lenses in the lens assembly. The light emitted from the lens assembly enters the reflecting prism P1 from the first working surface. The reflecting prism P1 can change the original straight-line direction of the light. Furthermore, the light is reflected twice inside the reflecting prism P1, namely the first reflection occurring at the second working surface and the second reflection occurring at the first working surface. Therefore, the back focal length of the lens can be folded inside the reflecting prism P1, so that the light emitted from the reflecting prism P1 can reach the imaging plane IMG after a shorter optical path, thereby shortening the back focal length of the lens. The light emitted from the reflecting prism P1 enters the compensating prism P2 through the fourth working surface. The compensating prism P2 corrects and deflects the light, meaning that the light is deflected both when it enters the fourth working surface and when it exits the compensating prism P2 through the fifth working surface. This ultimately ensures that the zero-field-of-view principal ray is perpendicularly incident on the imaging surface IMG of the imaging chip. This imaging chip can be vertically mounted inside the lens module. Without the compensating prism P2 for correction, the imaging surface IMG would often be tilted, making it inconvenient to install the imaging chip inside the lens module. Furthermore, the prism setup in this embodiment only reflects the light twice because if there is only one reflection, although the direction of the light is changed, it still occupies a relatively long space in the reflected direction for use as the back focal length of the lens, making the camera body larger. If there are three or more reflections, more than three reflecting surfaces are required, making the prism structure more complex and occupying a larger space, resulting in a larger camera body. Therefore, the telephoto lens of this embodiment, by reasonably allocating the optical power, spacing and refractive index of each lens in the lens assembly, as well as the folding of the back focal path of the lens by the reflecting prism P1, and the correction and deflection of the light by the compensating prism P2, can provide a telephoto lens with a large aperture and a large target surface. The height of the telephoto lens can be reduced by using the reflecting prism P1, and the imaging chip can be set vertically by using the compensating prism P2, which facilitates the installation of the imaging chip.

[0037] In an exemplary embodiment, according to the telephoto lens of this application, the compensation prism P2 is a wedge prism, and the fourth working surface and the fifth working surface form a wedge angle. Since the compensation prism P2 is a wedge prism, the fourth and fifth working surfaces can serve as two planes forming the wedge angle. This structure is simple and can achieve light deflection, allowing the zero-field-of-view principal ray to be perpendicularly incident on the imaging surface IMG of the imaging chip, facilitating the vertical installation of the imaging chip inside the lens module.

[0038] In an exemplary embodiment, the telephoto lens according to this application uses a trapezoidal prism P1. If the telephoto prism P1 is a wedge-shaped prism, then the second and third working surfaces can serve as the waist of the trapezoidal prism, and the upper and lower bases of the trapezoidal prism are parallel, facilitating installation and fixation. However, this invention is not limited to this; the telephoto prism P1 can also be a prism of other shapes, such as a triangular prism.

[0039] In an exemplary embodiment, according to the telephoto lens of this application, the reflecting prism P1 is an isosceles trapezoidal prism. The reflecting prism P1 is an isosceles wedge prism, thus eliminating the need to distinguish the two sides of the trapezoidal prism, facilitating installation.

[0040] In an exemplary embodiment, the telephoto lens according to this application may have a reflective coating on its second working surface. This ensures that light is completely reflected when reflected by the second working surface, reducing the risk of light being refracted out of the refraction prism P1 during the first reflection on the second working surface. It is understood that the first working surface may also be coated with a reflective coating to ensure complete reflection of light, reducing the risk of light being refracted out of the refraction prism P1 during the second reflection on the first working surface.

[0041] In an exemplary embodiment, the telephoto lens according to this application may have a chamfered or rounded corner. By chamfering or rounding the corner, the planar length of the telephoto lens P1, such as the lateral length of the first working surface, can be reduced, thereby reducing the overall lateral length of the telephoto lens P1. This saves internal space in the lens module, helps improve module reliability, and reduces stray light.

[0042] In an exemplary embodiment, according to the telephoto lens of this application, the fourth working surface of the compensation prism P2 coincides with the third working surface of the reflecting prism P1. That is, the compensation prism P2 and the reflecting prism P1 are in a surface-coinciding relationship, and the two can be glued together or separated.

[0043] In an exemplary embodiment, according to the telephoto lens of this application, the compensation prism P2 and the reflecting prism P1 constitute a combined prism. For example... Figure 1 As shown, not only does the fourth working surface of the compensating prism P2 coincide with the third working surface of the reflecting prism P1, but the length of the fourth working surface of the compensating prism P2 is also equal to the length of the third working surface of the reflecting prism P1. Therefore, the compensating prism P2 can be used as a compensating element on the third working surface of the reflecting prism P1. The compensating prism P2 and the reflecting prism P1 can form a combined prism, which can be used for light offset compensation and is easy to install.

[0044] In an exemplary embodiment, the telephoto lens according to this application satisfies Ab5>40 and Ab6>40, wherein the Abbe coefficient of the reflecting prism P1 is Ab5 and the Abbe coefficient of the compensating prism P2 is Ab6. By controlling the values ​​of Abbe coefficient Ab5 of the reflecting prism P1 and Abbe coefficient Ab6 of the compensating prism P2, large chromatic aberrations introduced by the reflecting prism P1 and the compensating prism P2 can be avoided, resulting in good image quality for the telephoto lens.

[0045] In an exemplary embodiment, for the telephoto lens according to the present application, 0.1 < ABS(N5 - N6) can be satisfied, where N5 is the refractive index of the retroreflective prism P1 and N6 is the refractive index of the compensating prism P2. Satisfying 0.1 < ABS(N5 - N6), by controlling the magnitude of the difference between the refractive index N5 of the retroreflective prism P1 and the refractive index N6 of the compensating prism P2, and a large refractive index difference can make the light deflection angle large, which is beneficial to achieving horizontal light output.

[0046] In an exemplary embodiment, for the telephoto lens according to the present application, M1 < 5.1 mm, M2 < 5 mm, and 0.5 < M1 / M2 < 1.5 can be satisfied, where M1 is the distance from the lens surface of the lens assembly to the first working surface, and M2 is the distance from the first working surface to the lower endpoint of the imaging surface. Satisfying M1 < 5.1 mm, M2 < 5 mm, and 0.5 < M1 / M2 < 1.5, by controlling the distance M1 from the lens surface of the lens assembly to the first working surface and the distance M2 from the first working surface to the lower endpoint of the imaging surface, it is beneficial to control the system height within a reasonable range, and thus beneficial to lens miniaturization.

[0047] In an exemplary embodiment, for the telephoto lens according to the present application, 1 < f’ / ImC < 2.2 can be satisfied, where f’ is the focal length of the telephoto lens and ImC is the imaging circle diameter. Satisfying 1 < f’ / ImC < 2.2, by controlling the ratio of the focal length f’ of the telephoto lens and the imaging circle diameter ImC within a defined range, it is possible to better balance a large aperture and a small field angle.

[0048] In an exemplary embodiment, for the telephoto lens according to the present application, 25° ≤ α1 ≤ 45° can be satisfied, where α1 is the angle between the first working surface and the second working surface of the retroreflective prism P1. Satisfying 25° ≤ α1 ≤ 45°, by controlling the angle α1 between the first working surface and the second working surface of the retroreflective prism P1, it is beneficial to ensure that the retroreflective prism P1 has a smaller thickness, and thus beneficial to lens miniaturization.

[0049] In an exemplary embodiment, for the telephoto lens according to the present application, 8° ≤ α2 ≤ 25° can be satisfied, where α2 is the angle between the fourth working surface and the fifth working surface of the compensating prism P2. Satisfying 8° ≤ α2 ≤ 25°, by controlling the angle α2 between the fourth working surface and the fifth working surface of the compensating prism P2, it is beneficial to make the compensating prism P2 have a certain optical path difference up and down.

[0050] In an exemplary embodiment, for the telephoto lens according to the present application, the lens assembly includes a first lens L1, a second lens L2, a third lens L3, and a fourth lens L4. The first lens L1 has a positive optical power, and the second lens L2 has a negative optical power. The first lens L1 has a positive optical power for converging light rays. The second lens L2 has a negative optical power for aberration correction. By combining the convex or concave surfaces of multiple lenses, various aberrations can be balanced to obtain a clear image.

[0051] In one exemplary embodiment, for the telephoto lens according to the present application, 1≤|f2 / f1|≤2 can be satisfied, where f1 is the focal length of the first lens L1 and f2 is the focal length of the second lens L2. Satisfying 1≤|f2 / f1|≤2 and controlling the focal lengths f1 of the first lens L1 and f2 of the second lens L2 is beneficial for aberration correction and achieving high resolution.

[0052] In one exemplary embodiment, for the telephoto lens according to the present application, 0.1<f1 / f’<1 can be satisfied, where f1 is the focal length of the first lens L1 and f’ is the focal length of the telephoto lens. Satisfying 0.1<f1 / f’<1 and controlling the ratio of the focal length f1 of the first lens L1 to the focal length f’ of the telephoto lens is beneficial for the first lens L1 to bear the main optical power of the optical system, which is beneficial for aberration correction and achieving high resolution.

[0053] In one exemplary embodiment, for the telephoto lens according to the present application, 0.1<|f2 / f’|<2 can be satisfied, where f2 is the focal length of the second lens L2 and f’ is the focal length of the telephoto lens. Satisfying 0.1<|f2 / f’|<2 and controlling the ratio of the focal length f2 of the second lens L2 to the focal length f’ of the telephoto lens is beneficial for the second lens L2 to maintain a weak optical power of the lens, avoiding large aberrations and enabling the telephoto lens to have good imaging quality.

[0054] In one exemplary embodiment, for the telephoto lens according to the present application, 1<|f3 / f’|<5 can be satisfied, where f3 is the focal length of the third lens L3 and f’ is the focal length of the telephoto lens. Satisfying 1<|f3 / f’|<5 and controlling the ratio of the focal length f3 of the third lens L3 to the focal length f’ of the telephoto lens is beneficial for the third lens L3 to maintain a weak optical power of the lens, avoiding large aberrations and enabling the telephoto lens to have good imaging quality.

[0055] In one exemplary embodiment, the telephoto lens according to the present application satisfies 1 < |f4 / f’| < 35, where the focal length of the fourth lens L4 is f4 and the focal length of the telephoto lens is f’. Satisfying 1 < |f4 / f’| < 35 facilitates maintaining a weak optical power of the lens of the fourth lens L4 by controlling the ratio of the focal length f4 of the fourth lens L4 to the focal length f’ of the telephoto lens, avoiding large aberrations, and enabling the telephoto lens to have good imaging quality.

[0056] In one exemplary embodiment, the telephoto lens according to the present application satisfies 0.05 < H3 / f’ < 0.15, where the thickness of the first lens L1 is H3 and the focal length of the telephoto lens is f’. Satisfying 0.05 < H3 / f’ < 0.15 can avoid difficult processing due to too thick lens by controlling the ratio of the thickness H3 of the first lens L1 to the focal length f’ of the telephoto lens within a certain range.

[0057] In one exemplary embodiment, the telephoto lens according to the present application satisfies 1.5 < Ab1 / Ab2 < 2.5, where the Abbe number of the first lens L1 is Ab1 and the Abbe number of the second lens L2 is Ab2. Satisfying 1.5 < Ab1 / Ab2 < 2.5 is conducive to correcting chromatic aberration by controlling the ratio of the Abbe number Ab1 of the first lens L1 to the Abbe number Ab2 of the second lens L2 within a certain range, enabling the telephoto lens to have good imaging quality.

[0058] In an exemplary embodiment, the telephoto lens according to the present application further includes an aperture STO, and the aperture STO can be disposed on the object side surface of the first lens L1 or between adjacent lenses.

[0059] In an exemplary embodiment, the telephoto lens according to the present application further includes a filter IR for correcting color deviation and / or a protective glass for protecting the photosensitive element located on the imaging surface IMG. In one exemplary embodiment, the filter IR can be disposed between the fifth working surface of the compensating prism P2 and the imaging surface IMG according to the present application, but the present invention is not limited thereto, and the filter IR can also be disposed at other positions, such as between the lens assembly and the first working surface of the folding prism P1, etc.

[0060] Based on the same inventive concept, an electronic device according to an exemplary embodiment of the present application includes the above-mentioned telephoto lens. The electronic device includes but is not limited to smartphones, tablet computers, laptop computers, gimbal shooting devices, surveillance cameras, and other imaging devices. The implementation of the electronic device can refer to the embodiments of the telephoto lens, and the repeated parts will not be described again.

[0061] 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.

[0062] The following describes in further detail, with reference to the accompanying drawings, specific embodiments of the telephoto lens applicable to the above-described embodiments.

[0063] Example 1

[0064] The following is for reference Figure 2 A telephoto lens according to Embodiment 1 of this application is described. Figure 2 A schematic diagram of the structure of a telephoto lens according to Embodiment 1 of this application is shown.

[0065] The telephoto lens of Embodiment 1 includes, from the object side to the image side, a lens assembly, a reflecting prism P1, and a compensating prism P2. The lens assembly may include a first lens L1, a second lens L2, a third lens L3, and a fourth lens L4. The aperture stop STO may be disposed on the object side of the first lens L1. The filter IR may be disposed between the compensating prism P2 and the imaging plane IMG.

[0066] The first lens L1 has positive optical power, with both its object-side and image-side surfaces being convex. The second lens L2 has negative optical power, with both its object-side and image-side surfaces being concave. The third lens L3 has negative optical power, with both its object-side and image-side surfaces being concave. The fourth lens L4 has positive optical power, with both its object-side and image-side surfaces being convex. The filter IR has both an object-side and an image-side surface. The reflecting prism P1 has a first, second, and third working surface. The compensating prism P2 has a fourth and a fifth working surface. Light from the object passes sequentially through the aperture STO, the first lens L1, the second lens L2, the third lens L3, and the fourth lens L4, then enters the first working surface and enters the reflecting prism P1. It undergoes a first reflection at the second working surface, a second reflection at the first working surface, exits through the third working surface, enters the fourth working surface and enters the compensating prism P2, exits through the fifth working surface, passes through the filter IR, and is finally imaged on the imaging surface IMG.

[0067] Table 1 shows the basic parameters of the telephoto lens of Example 1, where the radius of curvature, thickness, and focal length are all in millimeters (mm).

[0068] Table 1:

[0069]

[0070] Wherein, L1 R1 represents the object-side surface of the first lens L1, L1 R2 represents the image-side surface of the first lens L1, L2 R1 represents the object-side surface of the second lens L2, L2 R2 represents the image-side surface of the second lens L2, L3 R1 represents the object-side surface of the third lens L3, L3 R2 represents the image-side surface of the third lens L3, L4 R1 represents the object-side surface of the fourth lens L4, L4 R2 represents the image-side surface of the fourth lens L4, P1 R1 represents the object-side surface of the reflecting prism P1 (i.e., the first working surface), P1 R2 represents the image-side surface of the reflecting prism P1 (i.e., the third working surface), P2 R1 represents the object-side surface of the compensating prism P2 (i.e., the fourth working surface), P2 R2 represents the image-side surface of the compensating prism P2 (i.e., the fifth working surface), IR R1 represents the object-side surface of the filter IR, and IR R2 represents the image-side surface of the filter IR.

[0071] In Embodiment 1, the object-side surface and image-side surface of any one of the first lens L1 to the fourth lens L4 are both even-order aspherical surfaces. The surface shape of each aspherical lens can be defined using, but is not limited to, the following aspherical formula:

[0072] ………………………………………………….(1)

[0073] Where Z represents the height along the optical axis, c is the reciprocal of the surface radius, k is the conic coefficient, and r is the aperture along the radial direction; α represents the aspherical coefficient, α1 represents the aspherical coefficient A2, α2 represents the aspherical coefficient A4, and so on. Table 2 gives the higher-order coefficients A2, A4, A6, A8, A10, A12, A14, and A16 that can be used for each aspherical mirror in Example 1.

[0074] Table 2:

[0075]

[0076] In Example 1, the telephoto lens has a focal length of 13.3mm, an aperture of f / 2.4, an imaging circle diameter of 8.16mm, and a field of view of 33°. The angle between the first and second working surfaces can be α1 = 30.0°. The angle between the fourth and fifth working surfaces can be α2 = 11.5°. The focal length of the first lens L1 is f1 = 6.624mm, and the focal length of the second lens L2 is f2 = -11.664mm. The relationship between the focal lengths f1 and f2 of the first lens L1 and the second lens L2 is |f2 / f1| = 1.761. The relationship between the focal length f1 of the first lens L1 and the focal length f' of the telephoto lens is f1 / f' = 0.498. The relationship between the focal length f2 of the second lens L2 and the focal length f' of the telephoto lens is |f2 / f'| = 0.877. The relationship between the focal length f3 of the third lens L3 and the focal length f' of the telephoto lens is |f3 / f'| = 2.932. The relationship between the focal length f4 of the fourth lens L4 and the focal length f' of the telephoto lens is |f4 / f'| = 5.056. The relationship between the thickness H3 of the first lens L1 and the focal length f' of the telephoto lens is H3 / f' = 0.099. The relationship between the Abbe coefficient Ab1 of the first lens L1 and the Abbe coefficient Ab2 of the second lens L2 is Ab1 / Ab2 = 2.188. The Abbe coefficient Ab5 of the reflecting prism P1 is 64.2, and the Abbe coefficient Ab6 of the compensating prism P2 is 54.7. The relationship between the refractive index N5 of the reflecting prism P1 and the refractive index N6 of the compensating prism P2 is ABS(N5-N6) = 0.140. The distance M1 from the lens surface of the lens assembly to the first working surface, and the distance M2 from the first working surface to the lower end point of the imaging surface, are related by M1=4.990, M2=3.540, and M1 / M2=1.41. The focal length f' of the telephoto lens and the imaging circle diameter ImC are related by f' / ImC=1.630.

[0077] Figure 3 The axial aberration diagram of the telephoto lens of Example 1 is shown. When the example pupil radius is 2.7700 mm, the focal point deviation formed by different wavelengths of light along the optical axis on the focal plane is less than 0.04 mm, and the aberration correction is good. Figure 4 The distortion diagram of the telephoto lens of Example 1 is shown, with optical distortion of less than 0.5%, which is very small. Figure 5 The MTF (Modulation Transfer Function) curve of the telephoto lens in Example 1 is shown. The MTF curve illustrates the transmission of image details (i.e., image contrast) at different spatial frequencies by the imaging system. At a spatial frequency of 125 lp / mm, the MTF value is greater than 0.5, indicating excellent resolution. According to... Figures 3 to 5It can be seen that the telephoto lens given in Example 1 can achieve good image quality.

[0078] Example 2

[0079] The following is for reference Figure 6 This application describes a telephoto lens according to Embodiment 2. For the sake of brevity, descriptions similar to those in Embodiment 1 are omitted in this embodiment. Figure 6 A schematic diagram of the structure of a telephoto lens according to Embodiment 2 of this application is shown.

[0080] The telephoto lens of Embodiment 2 includes, from the object side to the image side, a lens assembly, a reflecting prism P1, and a compensating prism P2. The lens assembly may include a first lens L1, a second lens L2, a third lens L3, and a fourth lens L4. The aperture stop STO may be disposed on the object side of the first lens L1. The filter IR may be disposed between the compensating prism P2 and the imaging plane IMG.

[0081] The first lens L1 has positive optical power, with both its object-side and image-side surfaces being convex. The second lens L2 has negative optical power, with both its object-side and image-side surfaces being concave. The third lens L3 has negative optical power, with both its object-side and image-side surfaces being concave. The fourth lens L4 has negative optical power, with both its object-side and image-side surfaces being convex. The filter IR has both an object-side and an image-side surface. The reflecting prism P1 has a first, second, and third working surface. The compensating prism P2 has a fourth and a fifth working surface. Light from the object passes sequentially through the aperture STO, the first lens L1, the second lens L2, the third lens L3, and the fourth lens L4, then enters the first working surface and enters the reflecting prism P1. It undergoes a first reflection at the second working surface, a second reflection at the first working surface, exits through the third working surface, enters the fourth working surface and enters the compensating prism P2, exits through the fifth working surface, passes through the filter IR, and is finally imaged on the imaging surface IMG.

[0082] Table 3 shows the basic parameters of the telephoto lens in Example 2, where the radius of curvature, thickness, and focal length are all in millimeters (mm).

[0083] Table 3:

[0084]

[0085] Table 4 shows the higher-order coefficients that can be used for each aspherical mirror in Example 2, wherein each aspherical surface shape can be defined by formula (1) given in Example 1 above.

[0086] Table 4:

[0087]

[0088] In Example 2, the telephoto lens has a focal length of 13.3mm, an aperture of f / 2.4, an imaging circle diameter of 8.16mm, and a field of view of 33°. The angle between the first and second working surfaces can be α1 = 30.0°. The angle between the fourth and fifth working surfaces can be α2 = 11.5°. The focal length of the first lens L1 is f1 = 5.870mm, and the focal length of the second lens L2 is f2 = 8.528mm. The relationship between the focal lengths f1 and f2 of the first lens L1 and the second lens L2 is |f2 / f1| = 1.453. The relationship between the focal length f1 of the first lens L1 and the focal length f' of the telephoto lens is f1 / f' = 0.441. The relationship between the focal length f2 of the second lens L2 and the focal length f' of the telephoto lens is |f2 / f'| = 0.641. The relationship between the focal length f3 of the third lens L3 and the focal length f' of the telephoto lens is |f3 / f'| = 1.461. The relationship between the focal length f4 of the fourth lens L4 and the focal length f' of the telephoto lens is |f4 / f'| = 31.110. The relationship between the thickness H3 of the first lens L1 and the focal length f' of the telephoto lens is H3 / f' = 0.099. The relationship between the Abbe coefficient Ab1 of the first lens L1 and the Abbe coefficient Ab2 of the second lens L2 is Ab1 / Ab2 = 2.188. The Abbe coefficient Ab5 of the reflecting prism P1 is 64.2, and the Abbe coefficient Ab6 of the compensating prism P2 is 54.7. The relationship between the refractive index N5 of the reflecting prism P1 and the refractive index N6 of the compensating prism P2 is ABS(N5-N6) = 0.140. The distance M1 from the lens surface of the lens assembly to the first working surface, and the distance M2 from the first working surface to the lower end of the imaging surface, are related by M1=4.970, M2=3.540, and M1 / M2=1.40. The relationship between the focal length f' of the telephoto lens and the imaging circle diameter ImC is f' / ImC=1.630.

[0089] Figure 7 The axial aberration diagram of the telephoto lens of Example 2 is shown. When the example pupil radius is 2.7700mm, the focal deviation formed by different wavelengths of light along the optical axis on the focal plane is less than 0.04mm, and the aberration correction is good. Figure 8 The distortion diagram of the telephoto lens of Example 2 is shown, with optical distortion of less than 0.5%, which is very small. Figure 9 The MTF (Modulation Transfer Function) curve of the telephoto lens in Example 2 is shown. The MTF curve illustrates the transmission of image details (i.e., image contrast) at different spatial frequencies by the imaging system. At a spatial frequency of 125 lp / mm, the MTF value is greater than 0.5, indicating excellent resolution. According to... Figures 7 to 9It can be seen that the telephoto lens given in Example 2 can achieve good image quality.

[0090] Example 3

[0091] The following is for reference Figure 10 This describes a telephoto lens according to Embodiment 3 of this application. In this embodiment, for the sake of brevity, descriptions similar to those in Embodiment 1 are omitted. Figure 10 A schematic diagram of the structure of a telephoto lens according to Embodiment 3 of this application is shown.

[0092] The telephoto lens of Embodiment 3 includes, from the object side to the image side, a lens assembly, a reflecting prism P1, and a compensating prism P2. The lens assembly may include a first lens L1, a second lens L2, a third lens L3, and a fourth lens L4. The aperture stop STO may be disposed on the object side of the first lens L1. The filter IR may be disposed between the compensating prism P2 and the imaging plane IMG.

[0093] The first lens L1 has positive optical power, with both its object-side and image-side surfaces being convex. The second lens L2 has negative optical power, with both its object-side and image-side surfaces being concave. The third lens L3 has positive optical power, with both its object-side and image-side surfaces being concave. The fourth lens L4 has negative optical power, with both its object-side and image-side surfaces being convex. The filter IR has both an object-side and an image-side surface. The reflecting prism P1 has a first, second, and third working surface. The compensating prism P2 has a fourth and a fifth working surface. Light from the object passes sequentially through the aperture STO, the first lens L1, the second lens L2, the third lens L3, and the fourth lens L4, then enters the first working surface and enters the reflecting prism P1. It undergoes a first reflection at the second working surface, a second reflection at the first working surface, exits through the third working surface, enters the fourth working surface and enters the compensating prism P2, exits through the fifth working surface, passes through the filter IR, and is finally imaged on the imaging surface IMG.

[0094] Table 5 shows the basic parameters of the telephoto lens in Example 3, where the radius of curvature, thickness, and focal length are all in millimeters (mm).

[0095] Table 5:

[0096]

[0097] Table 6 shows the higher-order coefficients that can be used for each aspherical mirror in Example 3, wherein each aspherical surface shape can be defined by formula (1) given in Example 1 above.

[0098] Table 6:

[0099]

[0100] In Example 3, the telephoto lens has a focal length of 13.3mm, an aperture of f / 2.4, an imaging circle diameter of 8.16mm, and a field of view of 33°. The angle between the first and second working surfaces can be α1 = 30.0°. The angle between the fourth and fifth working surfaces can be α2 = 11.5°. The focal length of the first lens L1 is f1 = 6.252mm, and the focal length of the second lens L2 is f1 = -9.390mm. The relationship between the focal lengths f1 and f2 of the first lens L1 and the second lens L2 is |f2 / f1| = 1.502. The relationship between the focal length f1 of the first lens L1 and the focal length f' of the telephoto lens is f1 / f' = 0.470. The relationship between the focal length f2 of the second lens L2 and the focal length f' of the telephoto lens is |f2 / f'| = 0.706. The relationship between the focal length f3 of the third lens L3 and the focal length f' of the telephoto lens is |f3 / f'| = 3.376. The relationship between the focal length f4 of the fourth lens L4 and the focal length f' of the telephoto lens is |f4 / f'| = 3.143. The relationship between the thickness H3 of the first lens L1 and the focal length f' of the telephoto lens is H3 / f' = 0.100. The relationship between the Abbe coefficient Ab1 of the first lens L1 and the Abbe coefficient Ab2 of the second lens L2 is Ab1 / Ab2 = 2.188. The Abbe coefficient Ab5 of the reflecting prism P1 is 64.2, and the Abbe coefficient Ab6 of the compensating prism P2 is 54.7. The relationship between the refractive index N5 of the reflecting prism P1 and the refractive index N6 of the compensating prism P2 is ABS(N5-N6) = 0.140. The distance M1 from the lens surface of the lens assembly to the first working surface, and the distance M2 from the first working surface to the lower end of the imaging surface, are related as follows: M1 = 5.050, M2 = 3.540, M1 / M2 = 1.43. The relationship between the focal length f' of the telephoto lens and the imaging circle diameter ImC is f' / ImC = 1.630.

[0101] Figure 11 The axial aberration diagram of the telephoto lens of Example 3 is shown. When the example pupil radius is 2.7700mm, the focal point deviation formed by different wavelengths of light along the optical axis on the focal plane is less than 0.05mm, and the aberration correction is good. Figure 12 The distortion diagram of the telephoto lens of Example 3 is shown, with optical distortion of less than 0.5%, which is very small. Figure 13 The MTF (Modulation Transfer Function) curve of the telephoto lens in Example 3 is shown. The MTF curve illustrates the transmission of image details (i.e., image contrast) at different spatial frequencies by the imaging system. At a spatial frequency of 125 lp / mm, the MTF value is greater than 0.5, indicating excellent resolution. According to... Figures 11 to 13It can be seen that the telephoto lens given in Example 3 can achieve good image quality.

[0102] In summary, Examples 1, 2, and 3 satisfy the relationships shown in Table 7.

[0103] Table 7:

[0104]

[0105] 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 invention involved in this application is not limited to 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 long focus lens characterized by, From the object side to the image side, comprising: a lens assembly having four pieces of lenses with refractive power, comprising a first lens, a second lens, a third lens and a fourth lens arranged in sequence, the first lens having positive refractive power, the second lens having negative refractive power, wherein the first lens is a biconvex lens, the second lens is a convex-concave lens, the third lens is a concave-convex lens, and the fourth lens is a convex-concave lens; a return prism comprising a first working surface, a second working surface and a third working surface; the light emitted by the lens assembly enters the return prism from the first working surface, is reflected for the first time to the first working surface via the second working surface, is reflected for the second time to the third working surface via the first working surface, and is emitted via the third working surface; a compensation prism comprising a fourth working surface and a fifth working surface; the light emitted by the return prism enters the compensation prism from the fourth working surface, and is emitted via the fifth working surface, so that the chief ray of zero field of view is perpendicular to the imaging surface of the imaging chip, which is vertically arranged inside the lens module; the focal length f' of the long-focus lens and the imaging circle diameter ImC satisfy: 1 < f' / ImC < 2.2; the focal length f1 of the first lens, the focal length f2 of the second lens, the focal length f3 of the third lens, the focal length f4 of the fourth lens and the focal length f' of the long-focus lens satisfy: 0.1 < |f1 / f'| < 1, 0.1 < |f2 / f'| < 2, 1 < |f3 / f'| < 5 and 1 < |f4 / f'| < 35.

2. The telephoto lens of claim 1, wherein the Abbe number Ab5 of the return prism and the Abbe number Ab6 of the compensation prism satisfy: Ab5 > 40 and Ab6 > 40.

3. The telephoto lens of claim 1, wherein, the refractive index N5 of the return prism and the refractive index N6 of the compensation prism satisfy: 0.1 < ABS(N5-N6) ≤ 0.

14.

4. The telephoto lens of claim 1, wherein, the included angle α1 between the first working surface and the second working surface satisfies: 25° ≤ α1 ≤ 45°.

5. The telephoto lens of claim 1, wherein, the included angle α2 between the fourth working surface and the fifth working surface satisfies: 8° ≤ α2 ≤ 25°.

6. The telephoto lens of claim 1, wherein, the focal length f1 of the first lens and the focal length f2 of the second lens satisfy: 1 ≤ |f2 / f1| ≤ 2.

7. An electronic device, comprising: a long-focus lens comprising any one of the long-focus lenses according to claims 1 to 6.

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