TELEPHONE LENS AND MOBILE DEVICE

Description

TECHNICAL FIELD

[0001] The invention relates to the field of optical lens technologies, and more particularly, to a telephoto lens and a mobile terminal. The invention is set out in the appended set of claims.BACKGROUND

[0002] In recent years, with the pursuit of the imaging quality of portable electronic products, dual cameras have become the standard equipment for mobile phone products. In order to achieve high-quality imaging effect, most mobile phones use a solution of "fixed-focus dual-camera", which is a combination of a wide-angle lens and a telephoto lens, therefore the mobile phone can not only perform wide-angle shooting, but also enlarge the scene clearly when shooting in the distance, so that the mobile phone can have a good shooting effect similar to that of signal lens reflex cameras.

[0003] In the conventional dual-camera products, the equivalent focal length ratio of the telephoto lens and the wide-angle lens is between 3 and 5 times, and the zoom ratio can reach 3 to 5 times when the two are used in combination. The zoom ratio is too small compared with the traditional zoom lens, so it is difficult to meet the requirements of miniaturization and high-definition imaging of portable electronic products.

[0004] CN 203480119 U (document D1) discloses an image pick-up lens for a solid-state imaging element including, in order from an object side to an image side, an aperture stop, a first lens of a meniscus shape having a positive refractive power with a convex surface facing the object side, a second lens having a positive refractive power with a concave surface facing the object side, and a third lens having a negative refractive power with a convex surface facing the object side near an optical axis.

[0005] CN 1769940 A (document D2) discloses an imaging lens is composed of a first lens with a convex face facing an object side with a positive refraction, an aperture diaphragm, a second lens with a convex face facing an image side with a positive refraction, and a third lens with a concave face facing the image side with a negative refraction.

[0006] CN 204883031 U (document D3) discloses a modular zoom contains a telephoto lens and a wide -angle lens, the modular zoom further includes an image processing module or an intelligent image processing system that processes obtained images and realizes zooming characteristics.SUMMARY

[0007] The objects of the disclosure are to provide a telephoto lens and a mobile terminal to solve the above problems. The invention is set out in the appended set of claims.

[0008] Compared with the related art, the telephoto lens and the mobile terminal provided by the disclosure can achieve a higher zoom ratio. The equivalent focal length of the telephoto lens provided by the disclosure and the conventional wide-angle lens is more than 8 times, that is, the telephoto lens provided by the disclosure can achieve zooming of more than 8 times when used in combination with the conventional wide-angle lens, thereby better satisfying the requirements of miniaturization and high-definition imaging of electronic products.

[0009] The advantages of the invention will be partially given in the following description, and some will become apparent from the following description, or be learned through the practice of the invention.BRIEF DESCRIPTION OF THE DRAWINGS

[0010] FIG. 1 is a schematic structural diagram of a telephoto lens in a first embodiment of the disclosure. FIG. 2 is a diagram showing field curvature curves of the telephoto lens in the first embodiment of the disclosure. FIG. 3 is a diagram showing axial spherical aberration curves of the telephoto lens in the first embodiment of the disclosure. FIG. 4 is a diagram showing lateral chromatic aberration curves of the telephoto lens in the first embodiment of the disclosure. FIG. 5 is a schematic structural diagram of a telephoto lens in a second embodiment of the disclosure. FIG. 6 is a diagram showing field curvature curves of the telephoto lens in the second embodiment of the disclosure. FIG. 7 is a diagram showing axial spherical aberration curves of the telephoto lens in the second embodiment of the disclosure. FIG. 8 is a diagram showing lateral chromatic aberration curves of the telephoto lens in the second embodiment of the disclosure. FIG. 9 is a schematic structural diagram of a telephoto lens in a third embodiment of the disclosure. FIG. 10 is a diagram showing field curvature curves of the telephoto lens in the third embodiment of the disclosure. FIG. 11 is a diagram showing axial spherical aberration curves of the telephoto lens in the third embodiment of the disclosure. FIG. 12 is a diagram showing lateral chromatic aberration curves of the telephoto lens in the third embodiment of the disclosure. FIG. 13 is a schematic structural diagram of a telephoto lens in a fourth embodiment of the disclosure. FIG. 14 is a diagram showing field curvature curves of the telephoto lens in the fourth embodiment of the disclosure. FIG. 15 is a diagram showing axial spherical aberration curves of the telephoto lens in the fourth embodiment of the disclosure. FIG. 16 is a diagram showing lateral chromatic aberration curves of the telephoto lens in the fourth embodiment of the disclosure. FIG. 17 is a schematic structural diagram of a mobile terminal in a fifth embodiment of the disclosure. FIG. 18 is a top view of the FIG. 17.

[0011] Reference numerals of main components: StopSTFirst lensL1Second lensL2Third lensL3Flat glassG1FilterG2

[0012] The following embodiments will further illustrate the invention with reference to the above drawings.DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0013] In order to facilitate a better understanding of the invention, the invention will be further explained below with reference to the accompanying drawings. The embodiments of the invention are shown in the drawings, but the invention is not limited to the above-mentioned preferred embodiments. Rather, these embodiments are provided to make the disclosure of the invention more sufficient.

[0014] The embodiment of the invention provides a telephoto lens. Form an object side to an imaging surface, the telephoto lens sequentially includes: a first lens having a positive refractive power, a second lens having a refractive power, a third lens having a negative refractive power, a flat glass, and a filter. An object side surface of the first lens is a convex surface, an image side surface of the third lens is a concave surface.

[0015] In some embodiments, the telephoto lens meets the expression: 0.75 < TTL / f < 2.0; where TTL represents a total optical lens of the telephoto lens, f represents a focal length of the telephoto lens. Satisfying the above expression can effectively shorten the total optical length of the telephoto lens and promote the miniaturization of the telephoto lens.

[0016] The flat glass meets the expression: N d4 > 1.8; where N d4 refers to a refractive index of the flat glass. The flat glass uses a material with high refractive index to facilitate the incidence of the light.

[0017] In some embodiments, the first lens is made of glass. Due to the temperature resistance of the glass material is better and the performance is more stable, the first lens is made of glass material, which can effectively achieve the effect of thermalization for the telephoto lens.

[0018] In some embodiments, the telephoto lens meets the expression: 3 < f / R 1 < 5; where f represents a focal length of the telephoto lens, R 1 represents a radius of curvature of the object side surface of the first lens. When the value of f / R 1 exceeds the lower limit, the refractive power of the first lens becomes larger, which is not conducive to ensuring the peripheral performance, and the eccentric sensitivity becomes larger. When the value of f / R 1 exceeds the upper limit, it is difficult to correct the chromatic aberration of the telephoto lens.

[0019] In some embodiments, the telephoto lens meets the expression: 1 < R 1 / R 6 < 2; where R 1 represents a radius of curvature of the object side surface of the first lens, R 6 represents a radius of curvature of the image side surface of the third lens. Satisfying the above expression can effectively improve the resolution of the margin field of the telephoto lens.

[0020] In some embodiments, the telephoto lens meets the expression: 0 < CT 2 / CT 1 < 2; where CT 1 represents a center thickness of the first lens, CT 2 represents a center thickness of the second lens. Satisfying the above expression can effectively shorten the total optical length of the telephoto lens and promote the miniaturization of the telephoto lens.

[0021] In some embodiments, the telephoto lens meets the expression: -5 < f 2 / f 1 < 5; where f 1 represents a focal length of the first lens, f 2 represents a focal length of the second lens. When the value of f / R 1 exceeds the lower limit, the refractive power and the eccentric sensitivity becomes larger; when the value of f / R 1 exceeds the upper limit, the refractive power becomes smaller, which is not conducive to maintaining miniaturization.

[0022] In some embodiments, the telephoto lens meets the expression: -1 < f 3 / f < 0; where f 3 represents a focal length of the third lens, f represents a focal length of the telephoto lens. When the value of f 3 / f exceeds the lower limit, high-order aberration will occur for off-axis lights, and the performance of the telephoto will deteriorate; when the value of f 3 / f exceeds the upper limit, it is relatively difficult to correct the field curvature and the coma, and the eccentric sensitivity becomes larger.

[0023] In some embodiments, the telephoto lens meets the expression: -2 < (R 3 + R 4 ) / (R 3 - R 4 ) < 5; where R 3 represents a radius of curvature of the object side surface of the second lens, R 4 represents a radius of curvature of the image side surface of the second lens. When the value of (R 3 + R 4 ) / (R 3 - R 4 ) exceeds the upper limit, the field curvature and the distortion increase excessively in the positive direction, and are difficult to correct. Conversely, when the value of (R 3 + R 4 ) / (R 3 - R 4 ) exceeds the lower limit, the field curvature and the distortion increase excessively in the negative direction, and also are difficult to correct.

[0024] In some embodiments, the telephoto lens meets the expression: -2 < R 4 / f 2 < 3; where R 4 represents a radius of curvature of the image side surface of the second lens, f 2 represents a focal length of the second lens. When the value of R 4 / f 2 exceeds the lower limit, the refractive power of R 4 becomes larger, which is not conducive to ensure the peripheral performance, and the eccentric sensitivity becomes larger; when the value of R 4 / f 2 exceeds the upper limit, it is difficult to correct the field curvature.

[0025] In some embodiments, at least one of the object side surface of the first lens, an image side surface of the first lens, an object side surface of the second lens, an image side surface of the second lens, an object side surface of the third lens, and the image side surface of the third lens is a aspheric surface. A stop is disposed between the object side and the first lens. Aspheric surface can make the telephoto lens have more control variables to reduce aberration.

[0026] The embodiment of the invention further provides a mobile terminal. The mobile terminal includes the telephoto lens as mentioned in any above embodiments, the mobile terminal further includes an image sensor, the image sensor is disposed on the imaging surface of the telephoto lens and configured to receive optical signals output by the telephoto lens and form electrical signals corresponding to the optical signals.

[0027] The shapes of aspheric surfaces of the optical lens provided by the embodiments of the invention satisfy the following equation: z = ch 2 1 + 1 − 1 + k c 2 h 2 + Bh 4 + Ch 6 + Dh 8 + Eh 10 + Fh 12 + Gh 14 + Hh 16 , where z represents a vector height between a position on the surface and a vertex of the surface along an optical axis of the lens, c represents a curvature of the vertex of the surface, K is a quadratic surface coefficient, h is a distance between the position on the surface and the optical axis, B is a fourth order surface coefficient, C is a sixth order surface coefficient, D is an eighth order surface coefficient, E is a tenth order surface coefficient, F is a twelfth order surface coefficient, G is a fourteenth order surface coefficient, H is a sixteenth order surface coefficient.

[0028] Compared with a conventional telephoto lens, the telephoto lens provided by the invention can achieve a higher zoom ratio. The zoom ratio refers to the ratio of the equivalent focal length of the telephoto lens to the equivalent focal length of the wide-angle lens under the premise of the same pixels. Equivalent focal length = actual focal length * focal length conversion factor; focal length conversion factor = 43.3 / the diagonal length of the target surface of the image sensor.

[0029] The equivalent focal length of the telephoto lens provided by the disclosure and the conventional wide-angle lens is more than 8 times, that is, the telephoto lens provided by the disclosure can achieve zooming of more than 8 times when used in combination with the conventional wide-angle lens, thereby better satisfying the requirements of miniaturization and high-definition imaging of electronic products.

[0030] The invention will be further described in the following multiple embodiments. In each of the following embodiments, the thickness and radius of curvature of each lens in the telephoto lens are different. For specific differences, refer to the parameter table in each embodiment.FIRST EMBODIMENT

[0031] Please refer to FIG.1, which is a structural diagram of a telephoto lens 10 provided in a first embodiment of the disclosure. From an object side to an imaging surface thereof, the telephoto lens 10 sequentially includes a stop ST, a first lens L1, a second lens L2, a third lens L3, a flat glass G1 and a filter G2.

[0032] The first lens L1 has a positive refractive power, an object side surface S1 of the first lens L1 is a convex surface and an image side surface S2 of the first lens L1 is a concave surface. The first lens is made of glass, and the object side surface S1 of the first lens L1 and the image side surface S2 of the first lens L1 are both aspheric surfaces. The second lens L2 has a positive refractive power, an object side surface S3 of the second lens L2 is a convex surface, an image side surface S4 of the second lens L2 is a concave surface. The third lens L3 has a negative refractive power, an object side surface S5 of the third lens L3 is a convex surface, an image side surface S6 of the third lens L3 is a concave surface.

[0033] Related parameters of each lens in the telephoto lens 10 provided by the first lens are shown in Table 1. Table 1Surface NO.SignSurface typeRadius of curvatureThicknessRefractive indexAbbe numberObject surface S0Flat surface-STStopFlat surface--1.498S1First lens L1Aspheric surface7.1301.3171.80840.921S2Aspheric surface9.5290.139S3Second lens L2Spherical surface10.3211.3631.69756.200S4Spherical surface44.1190.048S5Third lens L3Spherical surface9.7110.4971.80525.477S6Spherical surface5.26510.000S7Flat glass G1Flat surface-13.0001.90137.054S8Flat surface-0.200S9Filter G2Flat surface-0.2101.51764.212S10Flat surface-7.272S11Imaging surfaceFlat surface--

[0034] The parameters of the aspheric surfaces of the first lens of this embodiment are shown in Table 2. Table 2Surface NO.kA 4 A 6 A 8 A 10 A 12 A 14 A 16 S1-0.3991.70E-053.53E-06-1.21E-061.13E-07-6.39E-091.87E-10-2.38E-12S207.18E-07-4.44E-06-1.18E-07-3.40E-092.77E-10-1.33E-110.00E+00

[0035] FIG. 2 shows field curvature curves of the telephoto lens 10 in this embodiment, FIG. 3 shows axial spherical aberration curves of the telephoto lens 10 in this embodiment, FIG. 4 shows lateral chromatic aberration curves of the telephoto lens 10 in this embodiment. As can be seen from the figures, the field curvature, the axial spherical aberration, the lateral chromatic aberration and the distortion of the telephoto lens 10 of this embodiment are all corrected well.SECOND EMBODIMENT

[0036] Please refer to FIG.5, which is a structural diagram of a telephoto lens 20 provided in this embodiment. The telephoto lens 20 in this embodiment is substantially similar to the telephoto lens 10 in the first embodiment expect that: a second lens L2 of the telephoto lens 20 has a negative refractive power, an object side surface S3 of the second lens L2 and an image side surface S4 of the second lens L2 are both aspheric surface, and the radius of curvature and the materials of each lens are different. Related parameters of each lens are shown in Table 3. Table 3Surface NO.SignSurface typeRadius of curvatureThicknessRefractive indexAbbe numberObject surface S0Flat surface-STStopFlat surface--1.345S1First lens L1Aspheric surface7.7961.7111.77349.503S2Aspheric surface43.5970.041S3Second lens L2Aspheric surface15.6940.4461.54455.951S4Aspheric surface8.6830.541S5Third lens L3Spherical surface7.5950.4881.94617.944S6Spherical surface5.70510.000S7Flat glass G1Flat surface-13.0001.90137.054S8Flat surface-0.200S9Filter G2Flat surface-0.2101.51764.212S10Flat surface-7.456S11Imaging surfaceFlat surface--

[0037] The parameters of the aspheric surfaces of the lenses of this embodiment are shown in Table 4. Table 4Surface NO.kA 4 A 6 A 8 A 10 A 12 A 14 A 16 S1-0.4162.77E-051.31E-05-1.46E-061.10E-07-6.10E-091.20E-10-8.29E-13S20.0001.67E-03-6.09E-05-2.20E-078.60E-090.00E+000.00E+000.00E+00S39.7822.24E-03-1.30E-050.00E+000.00E+000.00E+000.00E+000.00E+00S41.954-1.64E-049.74E-050.00E+000.00E+000.00E+000.00E+000.00E+00

[0038] FIG. 6 shows field curvature curves of the telephoto lens 20 in this embodiment, FIG. 7 shows axial spherical aberration of the telephoto lens 20 in this embodiment, FIG. 8 shows lateral chromatic aberration curves of the telephoto lens 20 in this embodiment. As can be seen from the figures, the field curvature, the axial spherical aberration, the lateral chromatic aberration, and the distortion of the telephoto lens 20 of this embodiment are all corrected well.THIRD EMBODIMENT

[0039] Please refer to FIG. 9, which is a structural diagram of a telephoto lens 30 provided in this embodiment. The telephoto lens 30 in this embodiment is substantially similar to the telephoto lens 10 in the first embodiment expect that: a first lens L1 and a second lens L2 of the telephoto lens 30 form a cemented lens, the second lens L2 has a negative refractive power, and the radius of curvature and the materials of each lens are different. Related parameters of each lens are shown in Table 5. Table 5Surface NO.SignSurface typeRadius of curvatureThicknessRefractive indexAbbe numberObject surface S0Flat surface-STStopFlat surface--1.462S1First lens L1Aspheric surface7.5302.0231.77349.503S2Second lens L2Spherical surface39.5220.4411.64833.842S3Spherical surface23.1010.452S4Third lens L3Spherical surface8.7100.4711.80525.477S5Spherical surface5.27010.000S6Flat glass G1Flat surface-13.0001.90137.054S7Flat surface-0.200S8Filter G2Flat surface-0.2101.51764.212S9Flat surface-7.153S10Imaging surfaceFlat surface--

[0040] The parameters of the aspheric surfaces of the lenses of this embodiment are shown in Table 6. Table 6Surface NO.kA 4 A 6 A 8 A 10 A 12 A 14 A 16 S1-0.197-5.81E-051.08E-05-1.68E-061.42E-07-6.81E-091.72E-10-1.76E-12

[0041] FIG. 10 shows field curvature curves of the telephoto lens 30 in this embodiment, FIG. 11 shows axial spherical aberration of the telephoto lens 30 in this embodiment, FIG. 12 shows lateral chromatic aberration curves of the lateral chromatic aberration of the telephoto lens 30 in this embodiment. As can be seen from the figures, the field curvature, the axial spherical aberration, the lateral chromatic aberration and the distortion of the telephoto lens 30 of this embodiment are all corrected well.FOURTH EMODIMENT

[0042] Please refer to FIG. 13, which is a structural diagram of a telephoto lens 40 provided in this embodiment. The telephoto lens 40 in this embodiment is substantially similar to the telephoto lens 10 in the first embodiment expect that: an image side surface of a second lens L2 of the telephoto lens 40 is a convex surface, and the radius of curvature and the materials of each lens are different. Related parameters of each lens are shown in Table 7. Table 7Surface NO.SignSurface typeRadius of curvatureThicknessRefractive indexAbbe numberObject surface S0Flat surface-STStopFlat surface--1.462S1First lens L1Aspheric surface7.3441.7461.76849.647S2Aspheric surface19.6490.327S3Second lens L2Spherical surface48.9850.9021.60365.460S4Spherical surface-110.6570.046S5Third lens L3Spherical surface11.2390.5091.74127.762S6Spherical surface5.43210.000S7Flat glass G1Flat surface-13.0001.90137.054S8Flat surface-0.200S9Filter G2Flat surface-0.2101.51764.212S10Flat surface-7.134S11Imaging surfaceFlat surface--

[0043] The parameters of the aspheric surfaces of the lenses of this embodiment are shown in Table 8. Table 8Surface NO.kA 4 A 6 A 8 A 10 A 12 A 14 A 16 S1-0.6851.56E-04-4.92E-061.08E-071.20E-08-1.50E-095.86E-11-1.39E-12S21.4547.57E-05-1.06E-053.36E-077.07E-09-1.24E-091.12E-110.00E+00

[0044] FIG. 14 shows field curvature curves of the telephoto lens 40 in this embodiment, FIG. 15 shows axial spherical aberration of the telephoto lens 40 in this embodiment, FIG. 16 shows lateral chromatic aberration curves of the telephoto lens 40 in this embodiment. As can be seen from the figures, the field curvature, the axial spherical aberration, the lateral chromatic aberration and the distortion of the telephoto lens 40 of this embodiment are all corrected well.

[0045] Table 9 shows the optical characteristics corresponding to the telephoto lens in the above four embodiments, including the total optical length TTL, the focal length f, the aperture number F #, and the field angle 2θ, and the value corresponding to each of the above conditional expression. Table 9ConditionFirst embodimentSecond embodimentThird embodimentFourth embodimentTTL34.04534.09333.95034.075f31.00031.00031.00431.000F#3.63.63.63.62θ8°8°8°8°TTL / f1.0981.1001.0951.099f / R 1 4.3483.9764.1174.221R 1 / R 6 1.3541.3671.4291.352CT 2 / CT 1 1.0350.2610.2240.517f 2 / f 1 0.677-3.037-3.1963.929f 3 / f-0.481-0.886-0.565-0.473(R 3 + R 4 ) / (R 3 - R 4 )-1.6113.4773.814-0.386R 4 / f 2 2.327-0.238-0.724-1.966

[0046] The total optical length of the telephoto lens provided by the disclosure exceeds 30mm, which is far more than the thickness of a mobile phone. When the telephoto lens is used in a mobile phone, the lens can be designed as a periscope lens imaging system using a reflective optical surface, which is embedded in the mobile phone to the meet the requirements of thin and light electronics product.

[0047] The focal lens of the telephoto lens provided by the disclosure reach 31mm, and the diagonal length of the image sensor matched with the telephoto lens is 5mm, and the calculation method of the equivalent focal length can be obtained: (1) focal length conversion factor = 43.3 / the diagonal length of the target surface of the image sensor = 43.3 / 5 = 8.66; (2) equivalent focal length = actual focal length * focal length conversion factor = 31 * 8.66 = 268.46mm. Therefore, the equivalent focal length of the telephoto lens provided by the disclosure can reach 268mm. Generally, the equivalent focal length of a conventional wide-angle lens is usually 20 ~30mm. When the telephoto lens provided by the disclosure is used in combination with a conventional wide-angle lens, the equivalent focal length ratio of the two is more than 8 times, that is, the telephoto lens provided by the disclosure can achieve zooming of more than 8 times when used in combination with the conventional wide-angle lens, thereby having better zoom imaging effects and better satisfying the requirements of miniaturization and high-definition imaging of electronic products.FIFTH EMBODIMENT

[0048] Please refer to FIG. 17 and FIG. 18, the embodiment provides a mobile terminal 100 including an image sensor 50 and a telephoto lens in any of the foregoing embodiments, such as the telephoto lens 10. The image sensor 50 is disposed on the imaging surface S11 of the telephoto lens 10, and configured to receive optical signals output by the telephoto lens and form electrical signals corresponding to the optical signals.

[0049] The image sensor 50 may be a Complementary Metal Oxide Semiconductor (CMOS) image sensor, or a Charge Coupled Device (CCD) image sensor.

[0050] The total optical length TTL of the telephoto lens provided by the disclosure can reach 34mm, which is far more than the thickness of the mobile terminal 100. When the telephoto lens 10 is disposed in the mobile terminal 100, the mobile terminal 100 further includes a first prism 61 and a second prism 62. The first prism 61 is disposed at an entrance of the telephoto lens, and the second prism 62 is disposed at an exit of the telephoto lens 10, thereby designing the telephoto lens 10 as a periscope lens imaging system (the incident light and the exit light are perpendicular to different planes) using reflective optical surfaces of the prisms, shortening a transmission distance of the optical path, and meeting the miniaturization requirements of the mobile terminal 100.

[0051] As shown in the perspective of FIG. 17, the first prism 61 turns the incident light (incident parallel to the paper surface) into the telephoto lens 10, and the second prism 62 turns the light emitted by the telephoto lens 10 again to form the exit light (exit perpendicular to the paper surface), the incident light and the exit light form a vertical relationship.

[0052] The mobile terminal 100 provided by the embodiment includes the telephoto lens 10, which can achieve a higher zoom ratio than a conventional telephoto lens, and can better satisfy the requirements of miniaturization and high-definition imaging of electronic products.

[0053] The above-mentioned embodiments are merely illustrative of several embodiments of the invention, and the description thereof is more specific and detailed, however is not to be construed as limiting the scope of the disclosure. It should be noted that various variations and modifications may be made by those skilled in the art. Therefore, the scope of the disclosure should be determined by the appended claims.

Claims

1. A telephoto lens (10), from an object side to an imaging surface thereof, sequentially comprising a stop surface (ST); a first lens (L1) having a positive refractive power, an object side surface (S1) of the first lens (L1) being convex; a second lens (L2) having a refractive power; a third lens (L3) having a negative refractive power, an image side surface (S6) of the third lens (L3) being concave; a flat glass (G1); and a filter (G2); characterized in that an object side surface (S3) of the second lens (L2) is convex; the flat glass (G1) meets the expression: Nd4 > 1.8, where Nd4 represents a refractive index of the flat glass (G1), and a focal length of the telephoto lens (10) is capable of reaching 31.000 mm.

2. The telephoto lens (10) as claimed in claim 1, wherein the telephoto lens (10) meets the expression: 0.75 < TTL / f < 2.0 ; where TTL represents a total optical lens of the telephoto lens (10), f represents a focal length of the telephoto lens (10).

3. The telephoto lens (10) as claimed in claim 1, wherein the focal length of the telephoto lens (10) is 31.000 mm or 31.004 mm.

4. The telephoto lens (10) as claimed in any one of claims 1-3, wherein the first lens (L1) is made of glass.

5. The telephoto lens (10) as claimed in any one of claims 1-4, wherein the telephoto lens (10) meets the expression: 3 < f / R 1 < 5 ; where f represents the focal length of the telephoto lens (10), R1 represents a radius of curvature of the object side surface (S1) of the first lens (L1).

6. The telephoto lens (10) as claimed in any one of claims 1-5, wherein the telephoto lens (10) meets the expression: 1 < R 1 / R 6 < 2 ; where R1 represents a radius of curvature of the object side surface (S1) of the first lens (L1), R6 represents a radius of curvature of the image side surface (S6) of the third lens (L3).

7. The telephoto lens (10) as claimed in any one of claims 1-6, wherein the telephoto lens (10) meets the expression: 0 < CT 2 / CT 1 < 2 ; where CT1 represents a center thickness of the first lens (L1), CT2 represents a center thickness of the second lens (L2).

8. The telephoto lens (10) as claimed in any one of claims 1-7, wherein the telephoto lens (10) meets the expression: − 5 < f 2 / f 1 < 5 ; where f1 represents a focal length of the first lens (L1), f2 represents a focal length of the second lens (L2).

9. The telephoto lens (10) as claimed in any one of claims 1-8, wherein the telephoto lens (10) meets the expression: − 1 < f 3 / f < 0 ; where f3 represents a focal length of the third lens (L3), f represents the focal length of the telephoto lens (10).

10. The telephoto lens (10) as claimed in any one of claims 1-9, wherein the telephoto lens (10) meets the expression: − 2 < R 3 + R 4 / R 3 − R 4 < 5 ; where R3 represents a radius of curvature of the object side surface (S3) of the second lens (L2), R4 represents a radius of curvature of the image side surface (S4) of the second lens (L2).

11. The telephoto lens (10) as claimed in any one of claims 1-10, wherein the telephoto lens (10) meets the expression: − 2 < R 4 / f 2 < 3 ; where R4 represents a radius of curvature of the image side surface (S4) of the second lens (L2), t2 represents a focal length of the second lens (L2).

12. The telephoto lens (10) as claimed in any one of claims 1-11, wherein at least one of the object side surface (S1) of the first lens (L1), an image side surface (S2) of the first lens (L1), the object side surface (S3) of the second lens (L2), an image side surface (S4) of the second lens (L2), an object side surface (S5) of the third lens (L3), and the image side surface (S6) of the third lens (L3) is a aspheric surface; and a stop (ST) is disposed between the object side (S0) and the first lens (L1).

13. A mobile terminal (100), comprising a telephoto lens (10) as claimed in any one of claims 1-12 and an image sensor (50), the image sensor (50) is disposed on an imaging surface (S11) of the telephoto lens (10) and configured to receive optical signals output by the telephoto lens (10) and form electrical signals corresponding to the optical signals.

14. The mobile terminal (100) as claimed in claim 13, wherein the mobile terminal (100) further comprises a first prism (61) and a second prism (62), the first prism (61) is disposed at an entrance of the telephoto lens (10), the second prism (62) is disposed at an exit of the telephoto lens (10), the first prism (61) turns incident lights into the telephoto lens (10), and the second prism (62) turns the lights again to form exit lights, the incident lights and the exit lights are perpendicular.

15. The mobile terminal (100) as claimed in claim 14, wherein the second prism (62) is disposed between the third lens (L3) and the image sensor (50).