A free-form periscope telephoto lens

Abstract

The present invention relates to the technical field of shooting equipment, and in particular to a free-form surface periscope telephoto lens. The free-form surface periscope telephoto lens provided in the present application is composed of a first free-form surface prism, a second free-form surface prism, a first lens with negative refractive power, and a second lens with positive refractive power. Through different arrangements, the propagation direction of light can be changed by 60 degrees to 90 degrees, thereby reducing the physical size of the entire optical system, making it more compact and reducing the length of the periscope telephoto lens.

Description

Technical Field

[0001] The present invention relates to the technical field of photographing equipment, and in particular to a free-form surface periscope telephoto lens. Background Art

[0002] With the continuous development of portable electronic devices such as mobile phones, users have higher and higher requirements for the camera performance of the camera modules of electronic devices, and telephoto lenses play an increasingly important role in modern smartphones. The optical zoom function of current smartphones usually relies on integrating multiple lenses in the camera system, each with a different focal length, so as to achieve different zoom magnifications. Among them, telephoto lenses play a key role in providing higher zoom magnifications. However, as the zoom magnification increases, especially when a higher magnification telephoto lens is required, the challenge is the limitation of smartphone design. The design of smartphones tends to be thin and light, which limits the physical size and length of a single telephoto lens, because traditional telephoto lenses require a long optical path when providing high-magnification zoom, which often causes the camera to protrude from the back of the phone, increasing the overall thickness of the phone. In this case, periscope cameras become a solution.

[0003] However, the current common telephoto camera design usually uses two right-angle prisms to fold the optical path, and cooperates with multiple plastic aspherical lenses. The role of the right-angle prism is to fold the optical path within a limited thickness to reduce the thickness of the module. However, in order to achieve the requirements of high resolution and optical performance, multiple complex aspherical lenses are required to correct optical distortion and chromatic aberration, which leads to an increase in the overall length and limits the optimization space of the design.

[0004] Therefore, there is an urgent need for a free-form periscope telephoto lens to reduce the overall length of the lens and optimize the volume and structure of the lens. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a free-form periscope telephoto lens, which reduces the overall length of the lens and optimizes the volume and structure of the lens.

[0006] The present invention provides a free-form surface periscope telephoto lens, comprising: from the object plane to the image plane along the optical axis, the following components are sequentially included:

[0007] The first free-form prism is used to bend the light 90 degrees:

[0008] A first lens having negative refractive power;

[0009] a second lens having positive refractive power;

[0010] The second free-form surface prism is used to fold the light 90 degrees again.

[0011] Furthermore, the first free-form surface prism and the second free-form surface prism each include: a light incident surface, a reflection surface and a light emitting surface;

[0012] The curved surface expressions of the light incident surface, the reflection surface and the light emitting surface are all:

[0013] ;

[0014] Where: x is the x-axis coordinate value, y is the y-axis coordinate value, z is the z-axis coordinate value, c is the curvature of the free-form surface vertex, r is the radial distance from the vertex of the surface to a point on the surface, k is the cone coefficient, N is the total number of Zernike polynomials, A is the coefficient of the Zernike polynomial, E i (x, y) is a Zernike polynomial.

[0015] Furthermore, the first free-form surface prism has a focal length range of 3 mm to 20 mm;

[0016] The second free-form surface prism has a focal length ranging from -5 mm to 30 mm.

[0017] Furthermore, the first lens and the second lens are aspherical lenses;

[0018] The combined focal length of the first lens and the second lens is in the range of 5 mm to 50 mm.

[0019] The present invention also provides a free-form surface periscope telephoto lens, comprising: along the optical axis from the object plane to the image plane, the following are included in sequence:

[0020] The first free-form surface prism is used to refract light, and the range of the refracted light is greater than or equal to 60 degrees and less than 90 degrees;

[0021] The second free-form surface prism is used to refract the light, and the range of the refracted light is greater than or equal to 60 degrees and less than 90 degrees;

[0022] A first lens having negative refractive power;

[0023] The second lens has positive refractive power.

[0024] Furthermore, the first free-form surface prism and the second free-form surface prism each include: a light incident surface, a reflection surface, a secondary reflection surface and a light emitting surface;

[0025] The curved surface expressions of the light incident surface, the reflection surface, the secondary reflection surface and the light emitting surface are all:

[0026] ;

[0027] Where: x is the x-axis coordinate value, y is the y-axis coordinate value, z is the z-axis coordinate value, c is the curvature of the free-form surface vertex, r is the radial distance from the vertex of the surface to a point on the surface, k is the cone coefficient, N is the total number of Zernike polynomials, A is the coefficient of the Zernike polynomial, E i (x, y) is a Zernike polynomial.

[0028] Furthermore, the secondary reflection surface is used for total reflection.

[0029] Furthermore, the first free-form surface prism has a focal length range of 3 mm to 20 mm;

[0030] The second free-form surface prism has a focal length ranging from -5 mm to 30 mm.

[0031] Furthermore, the first lens and the second lens are aspherical lenses;

[0032] The combined focal length of the first lens and the second lens is in the range of 5 mm to 50 mm.

[0033] The embodiments of the present invention have the following technical effects:

[0034] The present invention can significantly simplify the optical path by introducing two free-form prisms to replace the traditional right-angle prisms. The free-form prisms can more effectively fold the optical path, reducing the number and complexity of the required lenses, thereby optimizing the overall optical structure. The free-form prisms can more effectively fold the optical path, thus significantly reducing the physical volume of the module, which is particularly important for thin and light devices such as smartphones, and can improve the compactness of product design and user experience while maintaining performance.

[0035] At the same time, the introduction of free-form prisms can more accurately control the refraction and reflection of the light path, which helps to reduce optical distortion and improve image clarity and color performance. Adding a small amount of plastic aspherical lenses can further improve optical performance and ensure high resolution and high-quality output of the camera. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0037] Figure 1 is a schematic structural flow chart of a free-form surface periscope telephoto lens provided in Embodiment 1 of the present invention;

[0038] Figure 2 This is a schematic structural flow chart of a free-form surface periscope telephoto lens provided in Embodiment 2 of the present invention;

[0039] Figure 3 is a light performance diagram provided by Embodiment 1 of the present invention;

[0040] Figure 4 is a TV distortion diagram provided by the first embodiment of the present invention;

[0041] Figure 5 is an optical distortion diagram provided by the first embodiment of the present invention;

[0042] Figure 6 is a point diagram provided by the first embodiment of the present invention;

[0043] Figure 7 is a light performance diagram provided by Embodiment 2 of the present invention;

[0044] Figure 8 is a TV distortion diagram provided by the second embodiment of the present invention;

[0045] Fig. 9 is an optical distortion diagram provided by the second embodiment of the present invention;

[0046] Fig.10 This is a point diagram provided by the second embodiment of the present invention. DETAILED DESCRIPTION

[0047] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention. Embodiment 1

[0048] Figure 1 is a flow chart of a free-form surface periscope telephoto lens provided by an embodiment of the present invention. Figure 1 , specifically including: along the optical axis from the object plane to the image plane, including:

[0049] The first free-form surface prism 110 is used to fold the light by 90 degrees:

[0050] A first lens 120 having negative refractive power;

[0051] A second lens 130 having positive refractive power;

[0052] The second free-form surface prism 140 is used to fold the light 90 degrees again.

[0053] Furthermore, the first free-form surface prism 110 and the second free-form surface prism 140 both include a light incident surface, a reflection surface and a light emitting surface.

[0054] Specifically, the incident surface of the first free-form surface prism 110 is used to receive the incident light of the lens, the reflecting surface reflects the light for the first time to change the direction of the light, and the light-emitting surface transmits the processed light to the first lens 120 with negative refractive power; the second lens 130 with positive refractive power is located on the light-emitting surface of the first lens 120 with negative refractive power; the light-incident surface of the second free-form surface prism 140 is located on the light-emitting surface of the second lens 130 with positive refractive power, and receives the light from the second lens 130 with positive refractive power, the reflecting surface reflects the light to maintain the internal propagation of the light, and the light-emitting surface transmits the processed light to the final imaging plane.

[0055] Furthermore, the functions of the first free-form surface prism 110 are to distribute optical power, correct off-axis phase difference, and turn the optical path to reduce the imaging space; the functions of the first lens 120 with negative refractive power and the second lens 130 with positive refractive power are to correct optical distortion and adjust the focal length; the function of the second free-form surface prism 140 is to provide negative optical power, correct off-axis phase difference, and turn the optical path again to reduce the imaging space.

[0056] The curved surface shapes of the light incident surface, the reflection surface and the light emitting surface are all:

[0057] ;

[0058] Where: x is the x-axis coordinate value, y is the y-axis coordinate value, z is the z-axis coordinate value, c is the curvature of the free-form surface vertex, r is the radial distance from the vertex of the surface to a point on the surface, k is the cone coefficient, N is the total number of Zernike polynomials, A is the coefficient of the Zernike polynomial, E i (x, y) is a Zernike polynomial.

[0059] Furthermore, the first free-form surface prism 110 has a focal length range of 3 mm to 20 mm, which is suitable for applications that require adjustment of optical focal length and optical path; the second free-form surface prism 140 has a focal length range of -5 mm to 30 mm, and the negative focal length is suitable for adjusting the optical path and imaging quality of the overall system.

[0060] Furthermore, the first lens 120 and the second lens 130 are aspherical lenses; the combined focal length range of the first lens 120 and the second lens 130 is 5 mm to 50 mm, which is suitable for achieving an equivalent focal length of 3.5X to 5X, and helps to deal with spherical aberration and chromatic aberration problems.

[0061] The design of the first free-form surface prism 110, the second free-form surface prism 140, the first lens 120, and the second lens 130 of the present embodiment 1 is specifically referred to the following table:

[0062] Table 1 (a) Lens specific design parameters

[0063]

[0064] The free-form surface coefficients of the first free-form surface prism 110 of the first embodiment are as follows:

[0065] Table 1 (b) Free-form surface parameters of the first free-form surface prism 110

[0066]

[0067] The free-form surface coefficients of the second free-form surface prism 140 of the first embodiment are as follows:

[0068] Table 1 (c) Free-form surface parameters of the second free-form surface prism 140

[0069]

[0070] The surface coefficients of the first lens 120 and the second lens 130 of the first embodiment are as follows:

[0071] Table 1 (d) Surface coefficients of the first lens 120 and the second lens 130

[0072]

[0073] Furthermore, Figure 3 is a light performance diagram provided by the first embodiment of the present invention, such as Figure 3 As shown in the figure, the light performance diagram is a quantitative description of the clarity of the lens imaging, including two factors: resolution and sharpness. The black solid line represents the diffraction limit-meridian, and the black dotted line represents the diffraction limit-sagittal. That is, the black line represents the diffraction limit, which is the maximum resolution value when there is no aberration. The purple solid line represents the meridian of the free-form surface lens provided in this embodiment, and the purple dotted line represents the sagittal of the free-form surface lens provided in this embodiment. Figure 3 It can be seen that the MTF curve is straight. The closer the MTF value is to the diffraction limit, the higher the resolution, which means that the imaging consistency of the lens from the center to the edge is good, the out-of-focus imaging of the lens is good, and the blur effect is natural.

[0074] Figure 4is a TV distortion diagram provided by the first embodiment of the present invention, which indicates the degree of distortion or deformation of the image formed by the lens on the object relative to the object itself. Figure 4 It can be seen that the blue dot is the actual light position, and the black line is the theoretical position. The closer the blue dot is to the intersection of the black line, the smaller the TV distortion is. It can be seen that the grid distortion of the free-form surface lens provided in this embodiment is small, and good imaging quality can be achieved.

[0075] Figure 5 is an optical distortion diagram provided by the first embodiment of the present invention, such as Figure 5 As shown in the left coordinate system, the horizontal coordinate represents the magnitude of the field curvature, in units of mm; the vertical coordinate represents the normalized image height, in units of mm; Figure 5 It can be seen that the black solid line represents the 0 position reference line; the green solid line represents the field curvature data of the free-form surface lens provided in this embodiment; the green dotted line represents the theoretically expected field curvature data; the green solid line and the green dotted line are close, proving that the field curvature in the horizontal direction of the free-form surface lens provided in this embodiment is effectively controlled, that is, when imaging, the difference between the image quality at the center and the image quality at the periphery is small; in the right coordinate system, the horizontal coordinate represents the size of the distortion, in %; the vertical coordinate represents the normalized image height, without a unit; Figure 5 It can be seen that the black solid line represents the 0 position reference line, and the green solid line represents the distortion size of the free-form surface lens provided in this embodiment. It can be seen that the distortion of the free-form surface lens provided in this embodiment is well corrected, the imaging distortion is small, and the requirement of low distortion is met.

[0076] Figure 6 is a spot diagram provided by the first embodiment of the present invention. The spot diagram refers to a diffuse pattern formed by many light rays emitted by a point light source after passing through the optical system, where the intersection points of the light rays with the image plane are no longer concentrated at the same point due to aberration, but are scattered in a certain range. Figure 6 As shown, the free-form surface lens provided by the embodiment of the present invention has a relatively concentrated diffusion pattern of light in each field of view and a relatively uniform distribution. There is no phenomenon that the diffusion pattern in a certain field of view is separated very far up and down with the wavelength. The root mean square radius values ​​(RMS radius) of the light at each field of view position of the free-form surface lens are 0.615μm, 0.556μm, 0.622μm, 1.131μm, 0.662μm, 0.602μm, 0.604μm, 1.570μm, and 1.795μm, respectively, indicating that the RMS radius of each field of view is less than 8μm, indicating that at all listed field of view positions, the focusing effect of the light is very good, there is almost no diffusion phenomenon, and high-resolution imaging can be achieved. Embodiment 2

[0077] Figure 2is another flow chart of a free-form surface periscope telephoto lens provided by an embodiment of the present invention, see Figure 2 , specifically including: along the optical axis from the object plane to the image plane, including:

[0078] The first free-form surface prism 110 is used to refract light, and the range of the refracted light is greater than or equal to 60 degrees and less than 90 degrees;

[0079] The second free-form surface prism 140 is used to refract the light, and the range of the refracted light is greater than or equal to 60 degrees and less than 90 degrees;

[0080] A first lens 120 having negative refractive power;

[0081] The second lens 130 has positive refractive power.

[0082] Furthermore, the first free-form surface prism 110 and the second free-form surface prism 140 include: a light incident surface, a reflection surface, a secondary reflection surface and a light emitting surface;

[0083] The light incident surface and the secondary reflection surface are the same curved surface;

[0084] Specifically, the incident surface of the first free-form surface prism 110 is used to receive the incident light of the lens, the reflecting surface reflects the light for the first time to change the propagation direction of the light, the secondary reflecting surface reflects the light for the second time for total reflection, and the light-emitting surface transfers the processed light to the second free-form surface prism 140; the light incident surface of the second free-form surface prism 140 receives the light of the first free-form surface prism 110, the reflecting surface reflects the light, the secondary reflecting surface is used for the second total reflection to ensure the complete reflection of the light inside the system, and the light-emitting surface transfers the light to the first lens 120 with negative refractive power; the second lens 130 with positive refractive power is located on the light-emitting surface of the first lens 120 with negative refractive power.

[0085] Furthermore, the functions of the first free-form surface prism 110 are to distribute optical power, correct off-axis phase difference, and turn the optical path to reduce the imaging space; the first lens 120 with negative refractive power and the second lens 130 with positive refractive power are used for correction of optical distortion and focal length adjustment; the functions of the second free-form surface prism 140 are to provide negative optical power, correct off-axis phase difference, and turn the optical path again to reduce the imaging space.

[0086] The curved surface shapes of the light incident surface, the reflection surface, the secondary reflection surface and the light emitting surface are:

[0087] ;

[0088] Where: x is the x-axis coordinate value, y is the y-axis coordinate value, z is the z-axis coordinate value, c is the curvature of the free-form surface vertex, r is the radial distance from the vertex of the surface to a point on the surface, k is the cone coefficient, N is the total number of Zernike polynomials, A is the coefficient of the Zernike polynomial, E i (x, y) is a Zernike polynomial.

[0089] Furthermore, the secondary reflection surface is used for total reflection.

[0090] Furthermore, the first free-form surface prism 110 allocates a focal length range of 3mm to 20mm, which is suitable for increasing the optical path and adjusting the optical focal length; the second free-form surface prism 140 allocates a focal length range of -5mm to 30mm, and works in conjunction with the first free-form surface prism 110 to achieve optimization and adjustment of the optical path.

[0091] Furthermore, the first lens 120 and the second lens 130 are aspherical lenses; the combined focal length range of the first lens 120 and the second lens 130 is 5 mm to 50 mm, which is suitable for achieving an equivalent focal length of 3.5X to 5X. Adjustment within this range helps to overcome the challenges of spherical aberration and chromatic aberration and ensure imaging quality.

[0092] The design of the first free-form surface prism 110, the second free-form surface prism 140, the first lens 120, and the second lens 130 of the second embodiment is specifically referred to the following table:

[0093] Table 2 (a) Lens specific design parameters

[0094]

[0095] The free-form surface coefficients of the first free-form surface prism 110 of the second embodiment are as follows:

[0096] Table 2 (b) Free-form surface parameters of the first free-form surface prism 110

[0097]

[0098] The free-form surface coefficients of the second free-form surface prism 140 of the second embodiment are as follows:

[0099] Table 2 (c) Free-form surface parameters of the second free-form surface prism 140

[0100]

[0101] The surface coefficients of the first lens 120 and the second lens 130 of the second embodiment are as follows:

[0102] Table 2 (d) Surface coefficients of the first lens 120 and the second lens 130

[0103]

[0104] Furthermore, Figure 7 is a light performance diagram provided by the second embodiment of the present invention, such as Figure 7 As shown in FIG. 1 , the light performance diagram is a quantitative description of the clarity of the lens imaging, including two factors: resolution and sharpness. The black solid line represents the diffraction limit-meridian, and the black dotted line represents the diffraction limit-sagittal. That is, the black line represents the diffraction limit, which is the maximum resolution value when there is no aberration. The green solid line represents the meridian of the free-form surface lens provided in this embodiment, and the green dotted line represents the sagittal of the free-form surface lens provided in this embodiment. Figure 7 It can be seen that the MTF curve is straight. The closer the MTF value is to the diffraction limit, the higher the resolution, which means that the imaging consistency of the lens from the center to the edge is good, the out-of-focus imaging of the lens is good, and the blur effect is natural.

[0105] Figure 8 is a TV distortion diagram provided by the second embodiment of the present invention, which indicates the degree of distortion or deformation of the image formed by the lens on the object relative to the object itself. Figure 8 It can be seen that the blue dot is the actual light position, and the black line is the theoretical position. The closer the blue dot is to the intersection of the black line, the smaller the TV distortion is. It can be seen that the grid distortion of the free-form surface lens provided in this embodiment is small, and good imaging quality can be achieved.

[0106] Fig. 9 is an optical distortion diagram provided by the second embodiment of the present invention, such as Fig. 9 As shown in the left coordinate system, the horizontal coordinate represents the magnitude of the field curvature, in units of mm; the vertical coordinate represents the normalized image height, in units of mm; Fig. 9 It can be seen that the black solid line represents the 0 position reference line; the green solid line represents the field curvature data of the free-form surface lens provided in this embodiment; the green dotted line represents the theoretically expected field curvature data; the green solid line and the green dotted line are close, proving that the field curvature in the horizontal direction of the free-form surface lens provided in this embodiment is effectively controlled, that is, when imaging, the difference between the image quality at the center and the image quality at the periphery is small; in the right coordinate system, the horizontal coordinate represents the size of the distortion, in %; the vertical coordinate represents the normalized image height, without a unit; Fig. 9 It can be seen that the black solid line represents the 0 position reference line, and the green solid line represents the distortion size of the free-form surface lens provided in this embodiment. It can be seen that the distortion of the free-form surface lens provided in this embodiment is well corrected in the horizontal direction, and the imaging distortion is small, meeting the requirement of low distortion.

[0107] Fig.10 The point diagram provided by the second embodiment of the present invention is a point diagram, which refers to a diffuse pattern formed by many light rays emitted by a point light source after passing through the optical system, where the intersection points of the light rays with the image plane are no longer concentrated at the same point due to aberration, but are scattered in a certain range. Fig.10 As shown, the free-form surface lens provided by the embodiment of the present invention has a relatively concentrated diffusion pattern of light in each field of view and a relatively uniform distribution. There is no phenomenon that the diffusion pattern in a certain field of view is separated very far up and down with the wavelength. The root mean square radius values ​​(RMS radius) of the light at each field of view position of the free-form surface lens are 0.615μm, 0.556μm, 0.622μm, 1.131μm, 0.662μm, 0.602μm, 0.604μm, 1.570μm, and 1.795μm, respectively, indicating that the RMS radius of each field of view is much smaller than 8μm, indicating that at all the listed field of view positions, the focusing effect of the light is very good, there is almost no diffusion phenomenon, and high-resolution imaging can be achieved.

[0108] The present invention can significantly simplify the optical path and the entire telephoto structure by introducing two free-form prisms to replace the traditional right-angle prisms. The free-form prism can more effectively fold the optical path, reduce the number and complexity of the required lenses, and thus optimize the overall optical structure. The free-form prism can more effectively fold the optical path and reduce the length of the telephoto lens, making smartphones thinner and lighter while maintaining performance, improving the compactness of product design and user experience.

[0109] It should be noted that the terms used in the present invention are only for describing specific embodiments, rather than limiting the scope of the present application. As shown in the present specification, unless the context clearly indicates an exception, the words "one", "a", "a kind of" and / or "the" do not specifically refer to the singular, but may also include the plural. The terms "include", "comprise" or any other variant thereof are intended to cover non-exclusive inclusion, so that the process, method or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method or device. In the absence of more restrictions, the elements defined by the sentence "include one..." do not exclude the presence of other identical elements in the process, method or device including the elements.

[0110] It should also be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. Unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", etc. should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be a connection between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0111] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the technical solutions of the embodiments of the present invention.

Claims

1. A free-form surface periscope telephoto lens, characterized in that: Along the optical axis from the object plane to the image plane, it includes: The first free-form prism is used to bend the light 90 degrees: A first lens having negative refractive power; a second lens having positive refractive power; The second free-form surface prism is used to fold the light 90 degrees again; The first free-form surface prism and the second free-form surface prism each include: a light incident surface, a reflection surface and a light emitting surface; The curved surface expressions of the light incident surface, the reflection surface and the light emitting surface are all: ； Where: x is the x-axis coordinate value, y is the y-axis coordinate value, z is the z-axis coordinate value, c is the curvature of the free-form surface vertex, r is the radial distance from the vertex of the surface to a point on the surface, k is the cone coefficient, N is the total number of Zernike polynomials, A is the coefficient of the Zernike polynomial, E i (x, y) is a Zernike polynomial; The first lens and the second lens are aspherical lenses; The combined focal length of the first lens and the second lens is in the range of 5 mm to 50 mm.

2. The free-form surface periscope telephoto lens according to claim 1, characterized in that: The first free-form surface prism has a focal length range of 3 mm to 20 mm; The second free-form surface prism has a focal length ranging from -5 mm to 30 mm.

3. A free-form periscope telephoto lens, characterized in that: Along the optical axis from the object plane to the image plane, it includes: The first free-form surface prism is used to refract light, and the range of the refracted light is greater than or equal to 60 degrees and less than 90 degrees; The second free-form surface prism is used to refract the light, and the range of the refracted light is greater than or equal to 60 degrees and less than 90 degrees; A first lens having negative refractive power; a second lens having positive refractive power; The first free-form surface prism and the second free-form surface prism each include: a light incident surface, a reflection surface, a secondary reflection surface and a light exiting surface; The curved surface expressions of the light incident surface, the reflection surface, the secondary reflection surface and the light emitting surface are all: ； Where: x is the x-axis coordinate value, y is the y-axis coordinate value, z is the z-axis coordinate value, c is the curvature of the free-form surface vertex, r is the radial distance from the vertex of the surface to a point on the surface, k is the cone coefficient, N is the total number of Zernike polynomials, A is the coefficient of the Zernike polynomial, E i (x, y) is a Zernike polynomial; The first lens and the second lens are aspherical lenses; The combined focal length of the first lens and the second lens is in the range of 5 mm to 50 mm.

4. The free-form surface periscope telephoto lens according to claim 3, characterized in that: The secondary reflection surface is used for total reflection.

5. The free-form surface periscope telephoto lens according to claim 3, characterized in that: The first free-form surface prism has a focal length range of 3 mm to 20 mm; The second free-form surface prism has a focal length ranging from -5 mm to 30 mm.

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