Folding optical path telephoto lens and electronic equipment

Abstract

The invention discloses a folded light path telephoto lens and electronic equipment. The folded light path telephoto lens comprises a lens assembly, a first prism and a second prism from an object side to an image side, the lens assembly comprises a plurality of lenses which are arranged in sequence; the first prism is arranged between the lens assembly and the imaging surface and comprises a first surface and a second surface, an acute angle is formed between the first surface and the second surface, and light emitted from the lens assembly penetrates into the first prism from the first surface and penetrates out of the first prism from the second surface; the second prism is located between the first prism and the imaging surface and comprises a third surface, the third surface and the second surface are attached to each other, and light emitted from the first prism penetrates into the second prism from the third surface, is reflected at least twice in the second prism and then is emitted to the imaging surface. According to the folding light path telephoto lens and the electronic equipment, the rear focus light path of the lens is folded, and the height of the lens can be shortened, and a long focus and a large aperture can be achieved.

Description

Technical Field

[0001] The present invention relates to the field of optical imaging technology, and in particular to a folded optical path telephoto lens and electronic equipment. Background Art

[0002] With the development of multifunctional electronic devices, people have higher and higher requirements for the image quality of electronic devices such as mobile phones, and the demand for zoom is increasing. Telephoto lenses can easily capture distant scenery, buildings, natural landscapes, etc., and can take clear distant photos through optical zoom.

[0003] However, the back focal length of the telephoto lens is too long, which causes the lens to be installed too high inside the phone, affecting the thickness of the phone. Therefore, the mainstream solutions all adopt the periscope solution, but the focal length and aperture of this solution restrict each other, and it is impossible to achieve telephoto and large aperture at the same time. Summary of the invention

[0004] In view of the above problems, the object of the present invention is to provide a folded optical path telephoto lens and electronic equipment, which fold the rear focal path of the lens and can be used to shorten the lens height and achieve a telephoto and large aperture. The present invention provides a folded optical path telephoto lens, which comprises a lens assembly, a first prism and a second prism from the object side to the image side; the lens assembly comprises a plurality of lenses arranged in sequence, and incident light passes through the plurality of lenses in sequence; the first prism is arranged between the lens assembly and an imaging surface, and comprises a first surface and a second surface, an acute angle is formed between the first surface and the second surface, and light emitted from the lens assembly enters the first prism from the first surface and exits the first prism from the second surface; the second prism is located between the first prism and the imaging surface, and comprises a third surface, the third surface and the second surface are attached to each other, and light emitted from the first prism enters the second prism from the third surface, and is emitted to the imaging surface after being reflected at least twice inside the second prism.

[0005] Optionally, the second prism also includes a fourth surface and a fifth surface; the light emitted from the first prism enters the second prism from the third surface, the fourth surface and the third surface are used to reflect the light twice internally, and the second prism emits the light from the fifth surface to the imaging surface.

[0006] Optionally, the fourth surface is provided with a reflective film.

[0007] Optionally, the first prism and the second prism are combined into a rectangular prism.

[0008] Optionally, the thickness H14 of the equivalent flat plate of the second prism, the refractive index N14 of the second prism, and the focal length f′ of the camera module satisfy: 1.3<(H14*N14) / f′<1.5.

[0009] Optionally, the thickness H13 of the equivalent flat plate of the first prism and the thickness H14 of the equivalent flat plate of the second prism satisfy: 3.5 <H14 / H13<5。

[0010] Optionally, a refractive index N13 of the first prism and a refractive index N14 of the second prism satisfy: N14-N13>0.

[0011] Optionally, the number of the plurality of lenses is N, and the first two lenses arranged in sequence from the object side to the image side are respectively a first lens and a second lens, and the focal length of the first lens is f1, and the focal length of the second lens is f2, satisfying: 15 <f1+f2<40。

[0012] Optionally, the thickness of the equivalent flat plate of the first prism is H13, the number of the plurality of lenses is N, N≥3, the plurality of lenses include a first lens to an N-th lens arranged in sequence from the object side to the image side, and the sum of the center thickness of the first lens to the N-th lens and the air gap H3+…H12 satisfies: 0.4 <H13 / (H3+…H12)<0.6。

[0013] The present invention also provides an electronic device, comprising the above-mentioned folded optical path telephoto lens.

[0014] The folded optical path telephoto lens and electronic device provided by the present invention fold the rear focus optical path of the lens inside the prism through the combination of the first prism and the second prism, so that the rear focus of the lens is folded to less than 1 / 2 of the original, which can be used to shorten the height of the lens. At the same time, the present invention adopts a prism structure. Compared with the existing periscope structure, the relative aperture of the lens is no longer restricted, and can be used to achieve a telephoto large aperture. The large aperture can have high resolution, shorten the exposure time, and can take clear photos in dark environments such as at night. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0016] Figure 1 A schematic diagram of the optical structure of a folded optical path telephoto lens according to an embodiment of the present application is shown.

[0017] Figure 2 Shows Figure 1 Schematic diagram of the prism equivalent plate of the folded optical path telephoto lens.

[0018] Figure 3 A schematic diagram of a prism equivalent flat plate of a folded optical path telephoto lens according to Example 1 of the present application is shown.

[0019] Figure 4 and Figure 5 The MTF curve and distortion diagram of the folded optical path telephoto lens of Example 1 are respectively shown.

[0020] Figure 6 A schematic diagram of a prism equivalent flat plate of a folded optical path telephoto lens according to Example 2 of the present application is shown.

[0021] Figure 7 and Figure 8 The MTF curve and distortion diagram of the folded optical path telephoto lens of Example 2 are respectively shown.

[0022] Fig. 9 A schematic diagram of a prism equivalent flat plate of a folded optical path telephoto lens according to Example 3 of the present application is shown.

[0023] Fig.10 and Fig.11 The MTF curve and distortion diagram of the folded optical path telephoto lens of Example 3 are respectively shown. DETAILED DESCRIPTION

[0024] The aforementioned and other technical contents, features and effects of the present invention will be clearly presented in the following detailed description of the preferred embodiments with reference to the drawings. Through the description of the specific implementation methods, the technical means and effects adopted by the present invention to achieve the intended purpose can be more deeply and specifically understood. However, the attached drawings are only for reference and illustration purposes, and are not used to limit the present invention. Some well-known parts may not be shown. In each of the drawings, the same elements are represented by similar reference numerals. For the sake of clarity, the various parts in the drawings are not necessarily drawn strictly in accordance with the actual proportions.

[0025] It should be understood that the terms "first", "second", "third", "fourth", etc. are only used to distinguish components or circuits with similar properties, rather than indicating or implying relative importance or a specific order. The terms "include", "comprises", or any other variation thereof, are intended to cover non-exclusive inclusion, and may include other elements not explicitly listed in addition to those listed elements.

[0026] In the drawings, the thickness, size and shape of the lenses have been slightly exaggerated for ease of explanation. Specifically, the shapes of the spherical or aspherical surfaces shown in the drawings are shown by way of example. That is, the shapes of the spherical or aspherical surfaces are not limited to the shapes of the spherical or aspherical surfaces shown in the drawings. The drawings are only examples and are not drawn strictly to scale.

[0027] In this article, the paraxial region refers to the region near the optical axis. If the lens surface is convex and the position of the convex surface 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 position of the concave surface 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 object is called the object side of the lens, and the surface of each lens closest to the imaging surface S16 is called the image side of the lens.

[0028] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0029] The features, principles and other aspects of the present application are described in detail below.

[0030] like Figure 1 As shown, according to the folded optical path telephoto lens of the exemplary embodiment of the present application, from the object side to the image side, it includes a lens assembly, a first prism L1 and a second prism L2. The lens assembly includes a plurality of lenses arranged in sequence; the incident light passes through the plurality of lenses in sequence. The first prism L1 is arranged between the lens assembly and the imaging surface S16, and includes a first surface S11 and a second surface S12, and there is an acute angle between the first surface S11 and the second surface S12. The light emitted from the lens assembly penetrates into the first prism L1 from the first surface S11, and passes out of the first prism L1 from the second surface S12; the second prism L2 is located between the first prism L1 and the imaging surface S16, and includes a third surface S13, and the third surface S13 and the second surface S12 are attached to each other. The light emitted from the first prism L1 penetrates into the second prism L2 from the third surface S13, and is reflected at least twice inside the second prism L2 before being emitted to the imaging surface S16.

[0031] Specifically, Figure 1As shown, the incident light passes through the lens assembly, the first prism L1 and the second prism L2 in sequence from the object side to the image side, and is imaged on the imaging surface S16. The imaging surface S16 is the surface where the lens finally forms the image. The lens assembly includes a plurality of lenses, examples of which include the first lens P1, the second lens P2, the third lens P3 and the fourth lens P4. Each lens has an object side surface and an image side surface S1-S8. The first prism L1 and the second prism L2 are used to change the original straight-line direction of the light. The light is refracted when it passes through the first surface S11 of the first prism L1 and when it passes through the second surface S12 of the first prism L1. Since there is an acute angle between the first surface S11 and the second surface S12, the light will be deflected as a whole when passing through the first prism L1. Then, the light is refracted when it passes through the third surface S13 of the second prism L2, and then reflected at least twice inside the second prism L2 ( Figure 1 For the sake of convenience, the prism and the direction of the light have been slightly changed), and then the light is refracted when passing through the second prism L2, and finally emitted to the imaging surface S16 for imaging, that is, the back focus optical path of the lens is folded at least twice inside the second prism L2, thereby shortening the optical path of the light from the second prism L2 to the imaging surface S16. Figure 2 As shown, the first prism L1 and the second prism L2 can be equivalent to equivalent plates of corresponding thicknesses, that is, the thicknesses of the equivalent plates of the first prism L1 and the second prism L2 can correspond to the optical paths of the light after the light passes through the first prism L1 and the second prism L2 after being folded and unfolded. Figure 1 and Figure 2 It can be seen that the second prism L2 folds the lens back focus optical path at least twice inside the prism, which correspondingly shortens the distance that the light travels from the second prism L2 to the imaging surface S16. Therefore, the folded optical path telephoto lens of this embodiment adopts a combination of two prisms, the first prism L1 and the second prism L2, to fold the lens back focus optical path inside the prism, so that the lens back focus is folded to less than 1 / 2 of the original, which can be used to shorten the lens height. At the same time, this embodiment adopts a prism structure, and compared with the existing periscope structure, the relative aperture of the lens is no longer restricted, which can be used to achieve a telephoto large aperture, and a large aperture can have high resolution, which can shorten the exposure time and can take clear photos in dark environments such as at night.

[0032] In an exemplary embodiment, according to the folded optical path telephoto lens of the present application, the second prism L2 further includes a fourth surface S14 and a fifth surface S15; the light emitted by the first prism L1 is incident on the second prism L2 from the third surface S13, the fourth surface S14 and the third surface S13 are used to reflect the light at least twice internally, and the second prism L2 emits the light from the fifth surface S15 to the imaging surface S16. The smaller the angle between the third surface S13 and the fourth surface S14, the more times the light is reflected between the third surface S13 and the fourth surface S14.

[0033] In one exemplary embodiment, according to the folded optical path telephoto lens of the present application, the second prism L2 further includes a fourth surface S14 and a fifth surface S15; the light emitted from the first prism L1 is incident on the second prism L2 from the third surface S13, the fourth surface S14 and the third surface S13 are used to reflect the light twice internally, and the second prism L2 emits the light from the fifth surface S15 to the imaging surface S16. In other words, the light first enters the second prism L2 through the third surface S13, then is reflected for the first time through the fourth surface S14, then is reflected for the second time through the third surface S13, and finally is emitted to the imaging surface S16 through the fifth surface S15. The second prism L2 reflects the light twice internally and then emits it to the imaging surface S16, folding the lens back focus optical path inside the prism, which can shorten the lens back focus length, thereby reducing the camera height and improving the user experience. At the same time, the light is reflected only twice on the fourth surface S14 and the third surface S13 of the second prism L2, which can be easily achieved by setting the angle between the first surface S11 and the second surface S12 and the angle between the third surface S13 and the fourth surface S14, thereby avoiding the situation where too many reflections may cause the light to be refracted into the first prism L1 and unable to reach the imaging surface S16.

[0034] In an exemplary embodiment, the folded optical path telephoto lens according to the present application further includes an IR filter for correcting color deviation and / or a protective glass for protecting the photosensitive element located on the imaging surface S16.

[0035] In an exemplary embodiment, according to the folded optical path telephoto lens of the present application, the first prism L1 is a prism including multiple sharp edges, for example, it can be a triangular prism, a wedge-shaped mirror, etc. The prism structure is relatively simple and can meet the requirements that the light emitted by the first prism L1 is emitted from the third surface S13 to the second prism L2, the fourth surface S14 and the third surface S13 are used to reflect the light twice internally, and the second prism L2 emits the light from the fifth surface S15 to the imaging surface S16.

[0036] In an exemplary embodiment, according to the folded optical path telephoto lens of the present application, the fourth surface S14 of the second prism L2 is provided with a reflective film. Thus, when the light is first reflected by the second prism L2 on the fourth surface S14, it can be ensured that the light can be completely reflected, reducing the risk of the light being refracted out of the second prism L2 when passing through the fourth surface S14.

[0037] In an exemplary embodiment, for the folded optical path telephoto lens according to the present application, the fourth surface S14 and the third surface S13 are arranged within a preset included angle range, for example, an acute angle greater than the preset included angle. This preset included angle can be correspondingly set according to the included angle between the first surface S11 and the second surface S12, so that when the light undergoes the second reflection of the second prism L2 on the third surface S13, it is a total reflection, which can ensure that the light can be completely reflected and reduce the risk of the light being refracted into the first prism L1 when passing through the third surface S13.

[0038] In an exemplary embodiment, for the folded optical path telephoto lens according to the present application, the included angle between the first surface S11 of the first prism L1 and the chief ray of the zero field of view is 90°, that is, no adjustment of a specific included angle is required when the lens assembly and the prism are installed, which can facilitate the assembly of the prism.

[0039] In an exemplary embodiment, for the folded optical path telephoto lens according to the present application, the first prism L1 and the second prism L2 are combined into a cuboid prism, which can facilitate the assembly of the first prism L1 and the second prism L2.

[0040] In another exemplary embodiment, for the folded optical path telephoto lens according to the present application, the first prism L1 and the second prism L2 are combined into a right trapezoidal prism. The waists of the right trapezoidal prism are respectively the first surface S11 of the first prism L1 and the fourth surface S14 of the second prism L2, which can facilitate the assembly of the first prism L1 and the second prism L2.

[0041] In an exemplary embodiment, the folded optical path telephoto lens according to the present application can satisfy: 1.3 < (H14 * N14) / f′ < 1.5; where, the thickness of the equivalent plate of the second prism L2 is H14, the refractive index of the second prism L2 is N14, and the focal length of the folded optical path telephoto lens is f′. H14 * N14 is the optical path of the optical system in the second prism L2. Controlling the optical path of the second prism L2 and the focal length of the folded optical path telephoto lens within a certain ratio range can make the system structure symmetrical and avoid excessive local dimensions.

[0042] In an exemplary embodiment, the folded optical path telephoto lens according to the present application can satisfy: 3.5 < H14 / H13 < 5; where, the thickness of the equivalent plate of the first prism L1 is H13, and the thickness of the equivalent plate of the second prism L2 is H14. Satisfying 3.5 < H14 / H13 < 5, by controlling the thicknesses of the equivalent plates of the first prism L1 and the second prism L2 within a certain ratio range, it is possible to avoid the light incident on the second prism L2 through the first prism L1 from overflowing inside the second prism L2, resulting in vignetting in the imaging system.

[0043] In an exemplary embodiment, the folded optical path telephoto lens according to the present application can satisfy: N14 - N13 > 0; where the refractive index of the first prism L1 is N13, and the refractive index of the second prism L2 is N14. Satisfying N14 - N13 > 0, by controlling the refractive indices of the first prism L1 and the second prism L2, a condition can be formed for total reflection of the second reflection of the light by the second prism L2 on the third surface S13, so as to ensure that the light can be completely reflected and reduce the risk of the light being refracted into the first prism L1 when passing through the third surface S13.

[0044] In an exemplary embodiment, the folded optical path telephoto lens according to the present application can satisfy: 15 < f1 + f2 < 40; where the number of multiple lenses is N, and the first two lenses arranged in sequence from the object side to the image side are the first lens P1 and the second lens P2 respectively. The focal length of the first lens P1 is f1, and the focal length of the second lens P2 is f2. Satisfying 15 < f1 + f2 < 40, by controlling the focal lengths of the first lens P1 and the second lens P2, the function of converging light can be achieved, and it can be avoided that the incident angle of the light incident on the optical system is too large, resulting in serious primary aberrations.

[0045] In an exemplary embodiment, the folded optical path telephoto lens according to the present application can satisfy: 0.4 < H13 / (H3 + … H12) < 0.6; where the thickness of the equivalent flat plate of the first prism L1 is H13, the number of multiple lenses is N, N ≥ 3, and the multiple lenses include the first lens P1 to the Nth lens arranged in sequence from the object side to the image side. The sum of the central thicknesses and air gaps of the first lens P1 to the Nth lens is H3 + … H12. Satisfying 0.4 < H13 / (H3 + … H12) < 0.6, by controlling the thickness of the equivalent flat plate of the first prism L1 and the sum of the central thicknesses and air gaps of the first lens P1 to the Nth lens, the thickness of the first prism L1 can be prevented from being too thick.

[0046] Based on the same inventive concept, an electronic device according to an exemplary embodiment of the present application includes the above-mentioned folded optical path telephoto lens. The electronic device includes but is not limited to smartphones, tablets, laptops, gimbal shooting devices, surveillance cameras, and other imaging devices. For the implementation of this electronic device, reference can be made to the embodiments of the folded optical path telephoto lens, and the repeated parts will not be elaborated here.

[0047] However, those skilled in the art should understand that without departing from the technical solutions claimed in the present application, the number of lenses constituting the optical imaging lens can be changed to obtain the various results and advantages described in this specification. For example, although four lenses are described as an example in the embodiment, the optical imaging lens is not limited to including four lenses. If necessary, the optical imaging lens may also include other numbers of lenses.

[0048] Specific embodiments of the folded optical path telephoto lens applicable to the above-mentioned embodiments are further described below with reference to the accompanying drawings.

[0049] Example 1 The following reference Figure 3 A folded optical path telephoto lens according to Example 1 of the present application is described. Figure 3 A schematic diagram of a prism equivalent flat plate of a folded optical path telephoto lens according to Example 1 of the present application is shown.

[0050] like Figure 3 As shown, the lens assembly includes a first lens P1, a second lens P2, a third lens P3 and a fourth lens P4, and the folded optical path telephoto lens includes, from the object side to the image side, an aperture STO, a first lens P1, a second lens P2, a third lens P3, a fourth lens P4, a filter IR, a first prism L1, a second prism L2 and an imaging surface S16.

[0051] The first lens P1 has positive optical power, its object side surface S1 is convex, and the image side surface S2 is a plane. The second lens P2 has positive optical power, its object side surface S3 is convex, and the image side surface S4 is convex. The third lens P3 has negative optical power, its object side surface S5 is concave, and the image side surface S6 is concave. The fourth lens P4 has positive optical power, its object side surface S7 is concave, and the image side surface S8 is convex. The filter IR has an object side surface S9 and an image side surface S10. The equivalent flat plate of the first prism L1 has a first surface S11, and the equivalent flat plate of the second prism L2 has a third surface S13 and a fifth surface S15. The light from the object passes through each surface S1-S15 in sequence and is finally imaged on the imaging surface S16.

[0052] Table 1 shows the basic parameters of the folded optical path telephoto lens of Example 1, wherein the units of the curvature radius and thickness are both millimeters (mm).

[0053] Table 1:

[0054] In Embodiment 1, the object side surface and the image side surface of any lens of the first lens P1 to the fourth lens P4 are both even-order aspherical surfaces, and the surface shape x of each aspherical lens can be defined by, but not limited to, the following aspherical formula: (1) Wherein, z is the distance vector height from the vertex of the aspheric surface when the aspheric surface is at a height of r along the optical axis; c is the paraxial curvature of the aspheric surface, c=1 / R (i.e., the paraxial curvature c is the reciprocal of the curvature radius R in Table 1 above); k is the cone coefficient; A 2 , A 4 , A 6 , A 8, A 10 , A 12 , A 14 and A 16 They are the correction coefficients for the second, fourth, sixth, eighth, tenth, twelfth, fourteenth, and sixteenth orders of aspheric surfaces.

[0055] Table 2 shows the high-order coefficients A of the aspherical mirror surfaces S1-S8 that can be used in Example 1. 2 , A 4 , A 6 , A 8 , A 10 , A 12 , A 14 and A 16 .

[0056] Table 2:

[0057] In this embodiment, the focal length of the folded optical path telephoto lens is 13.5 mm, the working band of the folded optical path telephoto lens is 410-650 nm, the aperture of the folded optical path telephoto lens is 2.4, the imaging circle of the folded optical path telephoto lens is 8.3 mm, and the total optical length is 18.43 mm; the relationship between the thickness H14 of the equivalent flat plate of the second prism L2, the refractive index N14 of the second prism L2 and the focal length f' of the folded optical path telephoto lens is: (H14*N14) / f'=1.481; the thickness H13 of the equivalent flat plate of the first prism L1 and the refractive index N14 of the second prism L2 are: The relationship between the thickness H14 of the equivalent flat plate is: H14 / H13=4.00; the relationship between the refractive index N13 of the first prism L1 and the refractive index N14 of the second prism L2 is: N14-N13=0.48; the relationship between the focal length f1 of the first lens P1 and the focal length f2 of the second lens P2 is: f1+f2=20.30; the relationship between the thickness H13 of the equivalent flat plate of the first prism L1, and the sum of the center thickness of the first lens P1 to the fourth lens P4 and the air gap H3+…H12 is: H13 / (H3+…H12)=0.46.

[0058] Figure 4 The MTF curve of the folded optical path telephoto lens of Example 1 is shown. The MTF (Modulation Transfer Function) curve is the variation of the degree of restoration of the details of the subject reproduced by the lens on the image plane as the spatial frequency changes. When the spatial frequency is 125lp / mm, the minimum MTF is greater than 0.35, which has good resolution. Figure 5The distortion diagram of the folded optical path telephoto lens of Example 1 is shown, and the distortion is less than 4%, which is very small. The folded optical path telephoto lens of Example 1 can achieve good imaging quality, and it adopts a combination of two prisms, the first prism L1 and the second prism L2, to fold the lens back focus optical path inside the prism, so that the back focus of the lens is folded to less than 1 / 2 of the original, which can be used to shorten the lens height and achieve a telephoto large aperture, and then the large aperture high resolution can be used to shorten the exposure time, and clear photos can be taken in dark environments such as at night.

[0059] Example 2 The following reference Figure 6 A folded optical path telephoto lens according to embodiment 2 of the present application is described. Figure 6 A schematic diagram of a prism equivalent flat plate of a folded optical path telephoto lens according to Embodiment 2 of the present application is shown. In this embodiment, for the sake of brevity, some descriptions similar to Embodiment 1 will be omitted.

[0060] like Figure 6 As shown, the lens assembly includes a first lens P1, a second lens P2, a third lens P3 and a fourth lens P4, and the folded optical path telephoto lens includes, from the object side to the image side, an aperture STO, a first lens P1, a second lens P2, a third lens P3, a fourth lens P4, a filter IR, a first prism L1, a second prism L2 and an imaging surface S16.

[0061] The first lens P1 has positive optical power, its object side surface S1 is convex, and the image side surface S2 is a plane. The second lens P2 has positive optical power, its object side surface S3 is convex, and the image side surface S4 is convex. The third lens P3 has negative optical power, its object side surface S5 is concave, and the image side surface S6 is concave. The fourth lens P4 has negative optical power, its object side surface S7 is concave, and the image side surface S8 is convex. The filter IR has an object side surface S9 and an image side surface S10. The equivalent flat plate of the first prism L1 has a first surface S11, and the equivalent flat plate of the second prism L2 has a third surface S13 and a fifth surface S15. The light from the object passes through each surface S1-S15 in sequence and is finally imaged on the imaging surface S16.

[0062] Table 3 shows the basic parameters of the folded optical path telephoto lens of Example 2, wherein the units of the curvature radius and thickness are both millimeters (mm).

[0063] Table 3:

[0064] Table 4 shows the high-order coefficients of each aspherical mirror surface that can be used in Example 2, wherein each aspherical surface shape can be defined by the formula (1) given in the above-mentioned Example 1.

[0065] Table 4:

[0066] In this embodiment, the focal length of the folded light path telephoto lens is 22 mm, the working band of the folded light path telephoto lens is 410-650 nm, the aperture of the folded light path telephoto lens is 2.4, the imaging circle of the folded light path telephoto lens is 8 mm, and the total optical length is 29.66 mm; the thickness H14 of the equivalent flat plate of the second prism L2, the refractive index N14 of the second prism L2 and the focal length f' of the folded light path telephoto lens have the relationship: (H14*N14) / f'=1.573; the thickness H13 of the equivalent flat plate of the first prism L1 and the refractive index N14 of the second prism L2 are the same as those of the second prism L2. The relationship between the thickness H14 of the effective flat plate is: H14 / H13=4.32; the relationship between the refractive index N13 of the first prism L1 and the refractive index N14 of the second prism L2 is: N14-N13=0.48; the relationship between the focal length f1 of the first lens P1 and the focal length f2 of the second lens P2 is: f1+f2=25.45; the relationship between the thickness H13 of the equivalent flat plate of the first prism L1, and the sum of the center thickness of the first lens P1 to the fourth lens P4 and the air gap H3+…H12 is: H13 / (H3+…H12)=0.51.

[0067] Figure 7 The MTF curve of the folded optical path telephoto lens of Example 2 is shown. The MTF (Modulation Transfer Function) curve is the variation of the degree of restoration of the details of the subject reproduced by the lens on the image plane as the spatial frequency changes. When the spatial frequency is 125lp / mm, the minimum MTF is greater than 0.5, which has good resolution. Figure 8 The distortion diagram of the folded optical path telephoto lens of Example 2 is shown, and the distortion is less than 2%, which is very small. The folded optical path telephoto lens of Example 2 can achieve good imaging quality, and it adopts a combination of two prisms, the first prism L1 and the second prism L2, to fold the lens back focus optical path inside the prism, so that the back focus of the lens is folded to less than 1 / 2 of the original, which can be used to shorten the lens height and achieve a telephoto large aperture, and then the large aperture high resolution can be used to shorten the exposure time, and clear photos can be taken in dark environments such as at night.

[0068] Example 3 The following reference Fig. 9 A folded optical path telephoto lens according to Example 3 of the present application is described. Fig. 9 The figure shows a schematic diagram of a prism equivalent flat plate of a folded optical path telephoto lens according to Embodiment 3 of the present application. In this embodiment, for the sake of brevity, some descriptions similar to Embodiment 1 will be omitted.

[0069] like Fig. 9As shown, the lens assembly includes a first lens P1, a second lens P2, a third lens P3 and a fourth lens P4, and the folded optical path telephoto lens includes, from the object side to the image side, an aperture STO, a first lens P1, a second lens P2, a third lens P3, a fourth lens P4, a filter IR, a first prism L1, a second prism L2 and an imaging surface S16.

[0070] The first lens P1 has positive optical power, its object side surface S1 is convex, and the image side surface S2 is a plane. The second lens P2 has positive optical power, its object side surface S3 is convex, and the image side surface S4 is concave. The third lens P3 has negative optical power, its object side surface S5 is convex, and the image side surface S6 is concave. The fourth lens P4 has positive optical power, its object side surface S7 is convex, and the image side surface S8 is concave. The filter IR has an object side surface S9 and an image side surface S10. The equivalent flat plate of the first prism L1 has a first surface S11, and the equivalent flat plate of the second prism L2 has a third surface S13 and a fifth surface S15. The light from the object passes through each surface S1-S15 in sequence and is finally imaged on the imaging surface S16.

[0071] Table 5 shows the basic parameters of the folded optical path telephoto lens of Example 3, wherein the units of the curvature radius and thickness are both millimeters (mm).

[0072] Table 5:

[0073] Table 6 shows the high-order coefficients of each aspherical mirror surface that can be used in Example 3, wherein each aspherical surface shape can be defined by the formula (1) given in the above Example 1.

[0074] Table 6:

[0075] In this embodiment, the focal length of the folded light path telephoto lens is 27 mm, the working band of the folded light path telephoto lens is 410-650 nm, the aperture of the folded light path telephoto lens is 2.4, the imaging circle of the folded light path telephoto lens is 8.1 mm, and the total optical length is 35 mm; the thickness H14 of the equivalent flat plate of the second prism L2, the refractive index N14 of the second prism L2 and the focal length f' of the folded light path telephoto lens have the relationship: (H14*N14) / f'=1.481; the thickness H13 of the equivalent flat plate of the first prism L1 and the refractive index N14 of the second prism L2 are the same as those of the first prism L1 and the second prism L2. The relationship between the thickness H14 of the effective flat plate is: H14 / H13=4.00; the relationship between the refractive index N13 of the first prism L1 and the refractive index N14 of the second prism L2 is: N14-N13=0.48; the relationship between the focal length f1 of the first lens P1 and the focal length f2 of the second lens P2 is: f1+f2=35.53; the relationship between the thickness H13 of the equivalent flat plate of the first prism L1, and the sum of the center thickness of the first lens P1 to the fourth lens P4 and the air gap H3+…H12 is: H13 / (H3+…H12)=0.55.

[0076] Fig.10 The MTF curve of the folded optical path telephoto lens of Example 3 is shown. The MTF (Modulation Transfer Function) curve is the variation of the degree of restoration of the details of the subject reproduced by the lens on the image plane as the spatial frequency changes. When the spatial frequency is 125lp / mm, the minimum MTF is greater than 0.4, which has good resolution. Fig.11 The distortion diagram of the folded optical path telephoto lens of Example 3 is shown, and the distortion is less than 1%, which is very small. The folded optical path telephoto lens of Example 3 can achieve good imaging quality. It uses a combination of two prisms, the first prism L1 and the second prism L2, to fold the lens back focus optical path inside the prism, so that the lens back focus is folded to less than 1 / 2 of the original, which can be used to shorten the lens height and achieve a telephoto large aperture, and then use the large aperture high resolution to shorten the exposure time, and can take clear photos in dark environments such as at night.

[0077] In summary, Example 1, Example 2 and Example 3 respectively satisfy the relationship shown in Table 9.

[0078] Table 9:

[0079] The above description is only a preferred embodiment of the present application and an explanation of the technical principles used. Those skilled in the art should understand that the scope of the invention involved in the present application is not limited to the technical solution formed by a specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the inventive concept. For example, the above features are replaced with (but not limited to) technical features with similar functions disclosed in the present application.

Claims

1. A folded optical path telephoto lens, characterized in that: From the object side to the image side includes: A lens assembly, the lens assembly comprising a plurality of lenses arranged in sequence, and incident light passes through the plurality of lenses in sequence; A first prism, wherein the first prism is disposed between the lens assembly and the imaging surface and comprises a first surface and a second surface, wherein an acute angle is formed between the first surface and the second surface, and light emitted from the lens assembly passes through the first prism from the first surface and passes through the first prism from the second surface; A second prism, wherein the second prism is located between the first prism and the imaging surface and comprises a third surface, wherein the third surface and the second surface are bonded to each other, and light emitted from the first prism passes through the second prism from the third surface and is reflected at least twice inside the second prism before being emitted to the imaging surface.

2. The folded optical path telephoto lens according to claim 1, characterized in that: The second prism also includes a fourth surface and a fifth surface; the light emitted from the first prism enters the second prism from the third surface, the fourth surface and the third surface are used to reflect the light twice internally, and the second prism emits the light from the fifth surface to the imaging surface.

3. The folded optical path telephoto lens according to claim 2, characterized in that: The fourth surface is provided with a reflective film.

4. The folded optical path telephoto lens according to claim 1, wherein: The first prism and the second prism are combined into a rectangular parallelepiped prism.

5. The folded optical path telephoto lens according to claim 1, characterized in that: The thickness H14 of the equivalent flat plate of the second prism, the refractive index N14 of the second prism, and the focal length f′ of the folded optical path telephoto lens satisfy: 1.3<(H14*N14) / f′<1.

5.

6. The folded optical path telephoto lens according to claim 1, characterized in that: The thickness H13 of the equivalent plate of the first prism and the thickness H14 of the equivalent plate of the second prism satisfy: 3.5 <H14 / H13<5。 7. The folded optical path telephoto lens according to claim 1, wherein: The refractive index N13 of the first prism and the refractive index N14 of the second prism satisfy: N14-N13>0.

8. The folded optical path telephoto lens according to claim 1, wherein: The number of the plurality of lenses is N, and the first two lenses arranged in sequence from the object side to the image side are the first lens and the second lens, respectively. The focal length of the first lens is f1, and the focal length of the second lens is f2, satisfying: 15 <f1+f2<40。 9. The folded optical path telephoto lens according to claim 1, characterized in that: The thickness of the equivalent plate of the first prism is H13, the number of the plurality of lenses is N, N ≥ 3, the plurality of lenses include the first lens to the Nth lens arranged in sequence from the object side to the image side, and the sum of the center thickness of the first lens to the Nth lens and the air gap is H3+…H12, satisfying: 0.4 <H13 / (H3+…H12)<0.6。 10. An electronic device, characterized in that: Comprising the folded optical path telephoto lens as described in any one of claims 1 to 9.

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