Automatic focusing lens

Abstract

The utility model discloses an automatic focusing lens, and relates to the technical field of lenses, the lens sequentially comprises a first lens group, a second lens group, an iris diaphragm and a third lens group from an object side to an imaging side, the first lens group has positive focal power, and during focusing, the position of the first lens group relative to an image surface is kept unchanged; the second lens group has negative focal power, and the second lens group moves along the optical axis during focusing; the third lens group has positive focal power, and during focusing, the position of the third lens group relative to the image surface is kept unchanged; the lens satisfies a conditional expression of-2.3 lt; (f1 + f3) / f2lt; -1.6); according to the utility model, the performance requirements of high resolution, large clear aperture, small chromatic aberration and small distortion can be met.

Description

Technical Field

[0001] This application relates to the field of lens technology, and more particularly to an autofocus lens. Background Technology

[0002] With societal development, the demand for autofocus lenses is increasing, and the requirements for these lenses are also rising. However, current telephoto autofocus lenses on the market generally suffer from drawbacks such as insufficient resolution, significant distortion, small aperture, and large chromatic aberration, failing to meet the high demands of telephoto autofocus photography.

[0003] Therefore, there is an urgent need to design a lens with high resolution, large aperture, small chromatic aberration and small distortion, while also meeting the shooting requirements of autofocus. Utility Model Content

[0004] The main objective of this application is to at least solve one of the technical problems existing in the prior art, and to propose an autofocus lens that can meet the performance requirements of high resolution, large aperture, small chromatic aberration and small distortion.

[0005] To achieve the above objectives, this utility model application proposes an autofocus lens, which, from the object side to the imaging side, sequentially includes: a first lens group, a second lens group, a variable aperture, and a third lens group. The first lens group has positive optical power, and its position relative to the image plane remains unchanged during focusing. The second lens group has negative optical power, and it moves along the optical axis during focusing. The third lens group has positive optical power, and its position relative to the image plane remains unchanged during focusing. The lens satisfies the following condition:

[0006]

[0007] Where f1 represents the focal length of the first lens group, f2 represents the focal length of the second lens group, and f3 represents the focal length of the third lens group.

[0008] An autofocus lens provided according to an embodiment of this utility model has at least the following beneficial effects: First, the second lens group with negative optical power can efficiently adjust the focusing distance when moving, while the first and third lens groups with positive optical power can stabilize the image plane position, suppress image plane shift during focusing, and improve imaging stability; Second, during focusing, the positions of the first and third lens groups relative to the image plane remain unchanged, and autofocus is achieved only by moving the second lens group, allowing the motor to quickly achieve autofocus function and improve focusing efficiency; Next, the variable aperture is placed between the second and third lens groups, which can optimize aberrations (such as field curvature and distortion) by adjusting the aperture position, and can dynamically balance the amount of light entering during focusing, improving adaptability under complex lighting conditions; In addition, by satisfying the conditional formulas that limit the focal length values ​​of the first, second, and third lens groups, the lens structure is optimized, so that the lens can achieve fast focusing while also meeting the performance requirements of high resolution, large aperture, small chromatic aberration, small distortion, and short optical length.

[0009] In some embodiments, the first lens group includes at least two lenses with a refractive index greater than 1.4 and less than 1.5.

[0010] In some embodiments, the first lens group includes, from the object side to the imaging side, a first lens having positive optical power, a second lens having positive optical power, a third lens having negative optical power, a fourth lens having positive optical power, and a fifth lens having negative optical power.

[0011] The refractive index of the second lens and the refractive index of the fourth lens are both greater than 1.4 and less than 1.5.

[0012] In some embodiments, the fourth lens and the fifth lens are combined to form a cemented doublet lens.

[0013] In some embodiments, the first lens, the second lens, and the third lens are all meniscus lenses.

[0014] In some embodiments, the second lens group includes a sixth lens having negative optical power.

[0015] In some embodiments, the refractive index of the sixth lens is greater than 1.5 and less than 1.6.

[0016] In some embodiments, the third lens group includes at least three lenses with an Abbe number greater than 30 and less than 40.

[0017] In some embodiments, the third lens group includes, from the object side to the imaging side, the following lenses in sequence: a seventh lens with positive optical power, an eighth lens with negative optical power, a ninth lens with positive optical power, a tenth lens with negative optical power, an eleventh lens with positive optical power, a twelfth lens with negative optical power, a thirteenth lens with positive optical power, and a fourteenth lens with negative optical power.

[0018] The Abbe number of the ninth lens, the tenth lens, and the eleventh lens are all greater than 30 and less than 40.

[0019] In some embodiments, the seventh lens, the eighth lens, the ninth lens, and the tenth lens are combined to form a cemented tetrap lens. Attached Figure Description

[0020] The accompanying drawings are provided to further understand the technical solution of this utility model and constitute a part of the specification. They are used together with the embodiments of this utility model to explain the technical solution of this utility model, and do not constitute a limitation on the technical solution of this utility model.

[0021] The present invention will be further described below with reference to the accompanying drawings and embodiments;

[0022] Figure 1 This is a schematic diagram of the overall structure of an autofocus lens provided by this utility model;

[0023] Figure 2 This is a schematic diagram of longitudinal chromatic aberration in an autofocus lens provided by this utility model;

[0024] Figure 3 This is a schematic diagram of field curvature distortion of an autofocus lens provided by this utility model;

[0025] Figure 4 This is a schematic diagram of the blur pattern of an autofocus lens provided by this utility model;

[0026] Figure 5 This is an MTF diagram of an autofocus lens provided by this utility model;

[0027] Figure 6 This is a schematic diagram of the MTF defocus curve of an autofocus lens provided by this utility model. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0029] It should be noted that the terms "first," "second," etc., in the specification, claims, and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing embodiments of this application only and is not intended to limit this application.

[0031] This utility model provides an autofocus lens that can meet the performance requirements of high resolution, large aperture, small chromatic aberration, and small distortion.

[0032] The embodiments of this utility model will be further described below with reference to the accompanying drawings.

[0033] Reference Figure 1 This utility model application proposes an autofocus lens, which, from the object side to the imaging side, includes: a first lens group G1, a second lens group G2, a variable aperture STO, and a third lens group G3. The first lens group G1 has positive optical power, and its position relative to the image plane remains unchanged during focusing. The second lens group G2 has negative optical power, and it moves along the optical axis during focusing. The third lens group G3 has positive optical power, and its position relative to the image plane remains unchanged during focusing. The lens satisfies the following condition:

[0034]

[0035] Where f1 represents the focal length of the first lens group G1, f2 represents the focal length of the second lens group G2, and f3 represents the focal length of the third lens group G3.

[0036] According to an embodiment of this utility model, an autofocus lens is provided. First, the second lens group G2, which has negative optical power, can efficiently adjust the focusing distance when moving, while the first lens group G1 and the third lens group G3, which have positive optical power, can stabilize the image plane position, suppress image plane shift during focusing, and improve imaging stability. Second, during focusing, the positions of the first lens group G1 and the third lens group G3 relative to the image plane remain unchanged, and autofocus is achieved by moving only the second lens group G2, which allows the motor to quickly achieve the autofocus function and improves focusing efficiency. Next, the variable aperture STO is placed between the second lens group G2 and the third lens group G3. It can optimize aberrations (such as field curvature and distortion) by adjusting the position of the aperture, and can also dynamically balance the amount of light entering during focusing, improving adaptability under complex lighting conditions. In addition, by satisfying the conditional formulas that limit the focal length values ​​of the first lens group G1, the second lens group G2, and the third lens group G3, the lens structure is optimized, so that the lens can achieve fast focusing while also meeting the performance requirements of high resolution, large aperture, small chromatic aberration, small distortion, and short optical length.

[0037] Understandably, when the conditional constraints on the focal lengths of the first lens group G1, the second lens group G2, and the third lens group G3 are met, firstly, the focal length of the second lens group G2 is controlled within a reasonable range, allowing for rapid focus switching with only minor displacement during focusing, effectively improving focusing efficiency; secondly, if the negative light focal length of the second lens group G2 is too strong, i.e., the absolute value of the focal length of the second lens group G2 is too small, it will lead to field curvature deterioration. The conditional constraints ensure that the focal lengths of the first lens group G1 and the third lens group G3 are within a reasonable range. The positive optical power is sufficient to offset the field degradation caused by the second lens group G2, thereby improving resolution. Next, by constraining the focal length ratio, the intensity matching of dispersion compensation can be ensured, which helps to reduce chromatic aberration. In addition, distortion is mainly caused by the asymmetrical propagation of the principal ray before and after the variable stop STO. By constraining the focal length ratio, the positive optical power of the first lens group G1 and the third lens group G3 forms an approximately symmetrical structure with the negative optical power of the second lens group G2, so that the deflection angle of the principal ray before and after the variable stop STO is nearly symmetrical, significantly reducing distortion.

[0038] Preferably, the overall focal length of the lens is 85mm.

[0039] Preferably, the total optical length of the autofocus lens is limited to the range of 115 mm to 120 mm.

[0040] Understandably, by keeping the total optical length of an autofocus lens within the range of 115 mm to 120 mm, it is possible to avoid an excessively long optical length, thereby reducing lens costs and assembly sensitivity.

[0041] In some embodiments, the first lens group G1 includes at least two lenses with a refractive index greater than 1.4 and less than 1.5.

[0042] Understandably, by selecting at least two lenses with moderate refractive indices to participate in the formation of the first lens group G1, it is possible to reduce the thickness and weight of the lenses while maintaining good image quality, thereby helping to reduce the size and weight of the entire optical system.

[0043] In some embodiments, the first lens group G1 includes, from the object side to the imaging side, a first lens 1 having positive optical power, a second lens 2 having positive optical power, a third lens 3 having negative optical power, a fourth lens 4 having positive optical power, and a fifth lens 5 having negative optical power.

[0044] The refractive index of the second lens 2 and the refractive index of the fourth lens 4 are both greater than 1.4 and less than 1.5.

[0045] It should be noted that by controlling the refractive index of the second lens 2 and the refractive index of the fourth lens 4 within the range of 1.4 to 1.5, the propagation path of light can be kept from being disturbed too much, and the propagation path of light in the optical element can be precisely controlled.

[0046] In some embodiments, the fourth lens 4 and the fifth lens 5 are combined to form a cemented doublet lens.

[0047] Understandably, combining two lenses with different dispersion characteristics—the fourth lens 4 with positive optical power and the fifth lens 5 with negative optical power—to form a cemented doublet lens allows their dispersion to compensate for each other, effectively optimizing and reducing chromatic aberration. Reduced chromatic aberration helps light of different wavelengths focus more accurately on the image plane, thus restoring true image colors. It also reduces the sensitivity to assembly tolerances on the production line. Furthermore, during assembly, there is no need to worry about changes in the relative positions of the lenses, which helps improve mass production yield.

[0048] In some embodiments, the first lens 1, the second lens 2, and the third lens 3 are all meniscus lenses.

[0049] Understandably, meniscus lenses can more precisely control the focusing position of light, reduce the scattering of light inside the lens and the influence of stray light, which helps to improve image contrast and sharpness, thereby optimizing the MTF value. In addition, meniscus lenses can correct the deflection of light when it passes through the lens, so that the light can be focused more accurately on the image plane, which helps to reduce image distortion caused by light deflection.

[0050] In some embodiments, the second lens group G2 includes a sixth lens 6 having negative optical power.

[0051] Preferably, the weight of the sixth lens 6 is less than 6.7 grams.

[0052] Understandably, the second lens group G2 uses a lightweight lens group consisting of a single lens as the focusing group, which requires less driving force and allows the motor to quickly achieve the autofocus function.

[0053] In some embodiments, the refractive index of the sixth lens 6 is greater than 1.5 and less than 1.6.

[0054] It should be noted that by controlling the refractive index of the sixth lens 6 within the range of 1.5 to 1.6, the propagation path of light can be kept from being disturbed too much, and the propagation path of light in the lens can be precisely controlled.

[0055] In some embodiments, the third lens group G3 includes at least three lenses with an Abbe number greater than 30 and less than 40.

[0056] Understandably, by selecting at least three high Abbe number lenses to form the third lens group G3, the focusing ability of the third lens group G3 on light of different wavelengths can be more precisely controlled, thereby effectively optimizing chromatic aberration and improving image quality.

[0057] In some embodiments, the third lens group G3 includes, from the object side to the imaging side, the following lenses in sequence: a seventh lens 7 with positive optical power, an eighth lens 8 with negative optical power, a ninth lens 9 with positive optical power, a tenth lens 10 with negative optical power, an eleventh lens 11 with positive optical power, a twelfth lens 12 with negative optical power, a thirteenth lens 13 with positive optical power, and a fourteenth lens 14 with negative optical power.

[0058] Among them, the Abbe number of the ninth lens 9, the tenth lens 10, and the eleventh lens 11 are all greater than 30 and less than 40.

[0059] It should be noted that by controlling the Abbe number of the ninth lens 9, the tenth lens 10, and the eleventh lens 11 within the range of 30 to 40, the focusing ability of the ninth lens 9, the tenth lens 10, and the eleventh lens 11 for different wavelengths of light can be controlled more precisely, thereby effectively optimizing chromatic aberration and improving image quality.

[0060] In some embodiments, the seventh lens 7, the eighth lens 8, the ninth lens 9, and the tenth lens 10 are combined to form a four-colloidal lens.

[0061] Understandably, by combining four positive and negative lenses—the seventh lens 7 with positive optical power, the eighth lens 8 with negative optical power, the ninth lens 9 with positive optical power, and the tenth lens 10 with negative optical power—into a four-cemented lens, chromatic aberration can be mutually compensated, further reducing chromatic aberration and helping to restore the true colors of the image; at the same time, it reduces the sensitivity of assembly tolerances on the production line; in addition, there is no need to worry about changes in the relative positions between the lenses during the assembly process of the four-cemented lens, which helps to improve the mass production yield.

[0062] In some embodiments, the first lens group G1 includes, from the object side to the imaging side, a first lens 1 having positive optical power, a second lens 2 having positive optical power, a third lens 3 having negative optical power, a fourth lens 4 having positive optical power, and a fifth lens 5 having negative optical power; the second lens group G2 includes a sixth lens 6 having negative optical power; the third lens group G3 includes, from the object side to the imaging side, a seventh lens 7 having positive optical power, an eighth lens 8 having negative optical power, a ninth lens 9 having positive optical power, a tenth lens 10 having negative optical power, an eleventh lens 11 having positive optical power, a twelfth lens 12 having negative optical power, a thirteenth lens 13 having positive optical power, and a fourteenth lens 14 having negative optical power.

[0063] It should be noted that the specific data for the above-described structural embodiment are shown in Table 1:

[0064] Table 1

[0065] Face number face shape radius of curvature thickness Refractive index Abbe number Object spherical endless endless 1 spherical 56.395721 7.6 2.000689 25.435062 2 spherical 137.760968 1.850056 3 spherical 41.289478 8.8 1.496998 81.594687 4 spherical 158.901548 3.150668 5 spherical 137.029148 1 1.740773 27.761693 6 spherical 27.492796 2.234981 7 spherical 34.698561 9.6 1.496998 81.594687 8 spherical -79.509437 1 1.846666 23.787324 9 spherical 1053.028593 2.58935 10 spherical 1000.00173 1 1.516797 64.212351 11 spherical 37.740252 18.616668 STO spherical endless 0.682319 13 spherical 84.239429 7 1.603001 65.45962 14 spherical -31.070911 1 1.761823 26.613203 15 spherical 42.506585 6.4 1.953749 32.318108 16 spherical -76.689724 1.2 1.647693 33.842283 17 spherical 61.284056 5.206638 18 spherical 58.047873 9.1 1.850136 30.060435 19 spherical -59.780155 0.15 20 spherical -184.399532 1 1.617998 63.405767 21 spherical 49.55537 1.064393 22 spherical 67.489847 4.75 1.846666 23.787324 23 spherical -549.25125 4.968094 24 spherical -36.335599 1 1.487491 70.41964 25 spherical 500 12.698307 26 spherical endless 2.5 1.516797 64.212351 27 spherical endless 1 IMA spherical endless

[0066] The surface number indicates the surface number of each lens from the object side to the image side. Furthermore, the lenses in the first lens group G1, the second lens group G2, the variable aperture STO, and the third lens group G3 were set up according to the data in Table 1, and experiments were conducted. The experimental results can be referenced... Figures 2 to 6 Furthermore, as shown in the figure, this lens can effectively meet the performance requirements of good aberration correction, low distortion, and high resolution; specifically, refer to... Figure 2 , Figure 2 This is a schematic diagram of longitudinal color difference. It shows that the focal shift of the color difference at the center is less than 50 micrometers, ensuring no color difference before and after focusing. (Refer to...) Figure 3 , Figure 3 The diagram illustrates field distortion, showing that the optical distortion of this optical system is less than 0.5%, resulting in very low distortion in actual shooting, with no visible distortion to the naked eye. (Refer to...) Figure 5 as well as Figure 6 , Figure 5 This is a schematic diagram of MTF. Figure 6The diagram shows the MTF defocus curve. It can be seen that the MTF is greater than 0.48 directly opposite the 30 line. In this area, the two characteristics of high resolution and defocus are highly concentrated, which can facilitate fast focusing.

[0067] The embodiments of the present utility model have been described in detail above with reference to the accompanying drawings. However, the present utility model is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present utility model.

Claims

1. An auto focus lens characterized by, From the object side to the imaging side in order: a first lens group having positive refractive power, the position of the first lens group relative to the image plane remaining unchanged when focusing; a second lens group having negative refractive power, the second lens group moving along the optical axis when focusing; a variable aperture; a third lens group having positive refractive power, the position of the third lens group relative to the image plane remaining unchanged when focusing; The lens satisfies the following conditional expression: Wherein f1 represents the focal length value of the first lens group, f2 represents the focal length value of the second lens group, and f3 represents the focal length value of the third lens group.

2. The auto focus lens according to claim 1, wherein, In the first lens group, at least two lenses with a refractive index greater than 1.4 and less than 1.5 are included.

3. The auto focus lens according to claim 2, wherein, The first lens group comprises, from the object side to the imaging side in order: a first lens with positive refractive power, a second lens with positive refractive power, a third lens with negative refractive power, a fourth lens with positive refractive power, and a fifth lens with negative refractive power. Wherein the refractive index of the second lens and the refractive index of the fourth lens are both greater than 1.4 and less than 1.

5.

4. The auto focus lens according to claim 3, wherein, The fourth lens and the fifth lens are combined into a double cemented lens.

5. The auto focus lens of claim 3, wherein, The first lens, the second lens, and the third lens are all meniscus lenses.

6. The auto focus lens of claim 1, wherein, The second lens group includes a sixth lens with negative refractive power.

7. The auto focus lens according to claim 6, wherein The refractive index of the sixth lens is greater than 1.5 and less than 1.

6.

8. The auto focus lens of claim 1, wherein, In the third lens group, at least three lenses with an Abbe number greater than 30 and less than 40 are included.

9. The auto focus lens according to claim 8, wherein, The third lens group comprises, from the object side to the imaging side in order: a seventh lens with positive refractive power, an eighth lens with negative refractive power, a ninth lens with positive refractive power, a tenth lens with negative refractive power, an eleventh lens with positive refractive power, a twelfth lens with negative refractive power, a thirteenth lens with positive refractive power, and a fourteenth lens with negative refractive power. Wherein the Abbe number of the ninth lens, the Abbe number of the tenth lens, and the Abbe number of the eleventh lens are all greater than 30 and less than 40.

10. The auto focus lens according to claim 9, wherein, The seventh lens, the eighth lens, the ninth lens, and the tenth lens are combined into a four-cemented lens.

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