Fixed focus optical system

Abstract

The utility model discloses a fixed-focus optical system, which relates to the technical field of optical systems and is provided with an object side and an image side which are oppositely arranged in the direction of an optical axis. The fixed-focus optical system comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens and an image plane which are sequentially arranged from the object side to the image side. Through the arrangement, the focal lengths of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens and the seventh lens are reasonably controlled through material combination and surface type distribution of the plurality of lenses of the fixed-focus optical system, and the focal lengths are enabled to be-8mlt; f1lt; 5 mm; the thickness is-30 mmlt; f2lt; f2lt; -20 mm;-20 mm; the thickness is 4 mmlt; f3lt; f3t; 7 mm; the thickness is 3 mmlt; f4lt; f4t; 6 mm; the thickness is-9 mmlt; f5lt; f5t; -4 mm; the thickness is 10 mmlt; f61t; f61t; 25 mm; the thickness is-25 mmlt; f7lt; f7lt; therefore, the fixed-focus optical system has good performances such as very small chromatic aberration and the like on the premise that the fixed-focus optical system has a large visual angle, high pixel and athermalization.

Description

TECHNICAL FIELD

[0001] The utility model relates to optical system technical field, especially a kind of fixed focus optical system. BACKGROUND

[0002] With the development of mobile internet, photos and influence present network sharing trend to record the point and drop of life, thus giving birth to action camera, and the corresponding optical lens demand of its supporting also higher and higher. Since action camera is used in extreme environment temperature, therefore, the lens matched is required extremely, needs to meet the great field of view, high-definition imaging effect, small volume portable and can adapt to the big temperature difference change without virtual focus. CONTENT OF UTILITY MODEL

[0003] The main purpose of the utility model is to provide a kind of fixed focus optical system, to improve the problem that the existing optical system cannot meet large field of view, high-definition and cannot adapt to the big temperature difference change without virtual focus simultaneously.

[0004] To achieve the above object, the fixed focus optical system provided by the utility model has the object side and the image side relatively arranged in the optical axis direction, the fixed focus optical system includes first lens, second lens, third lens, fourth lens, fifth lens, sixth lens, seventh lens and image plane arranged in sequence from the object side to the image side, the focal length of the first lens is f1, the focal length of the second lens is f2, the focal length of the third lens is f3, the focal length of the fourth lens is f4, the focal length of the fifth lens is f5, the focal length of the sixth lens is f6, the focal length of the seventh lens is f7, and the fixed focus optical system meets the following conditions:

[0005] -8mm < f1 < -5mm; and -30mm < f2 < -20mm; and 4mm < f3 < 7mm; and 3mm < f4 < 6mm; and -9mm < f5 < -4mm; and 10mm < f6 < 25mm; and -25mm < f7 < -12mm;

[0006] Among them, the first lens and the third lens are glass spherical lenses, and the second lens, the fourth lens, the fifth lens, the sixth lens and the seventh lens are plastic aspherical lenses.

[0007] In an embodiment, the refractive index of the first lens is n1, and 1.50 ≤ n1 ≤ 1.75;

[0008] The refractive index of the second lens is n2, and 1.60 ≤ n2 ≤ 1.70;

[0009] The refractive index of the third lens is n3, and 1.75 ≤ n3 ≤ 1.95;

[0010] a refractive index of the fourth lens is n4, 1.50 ≤ n4 ≤ 1.60;

[0011] a refractive index of the fifth lens is n5, 1.60 ≤ n5 ≤ 1.70;

[0012] a refractive index of the sixth lens is n6, 1.50 ≤ n6 ≤ 1.60;

[0013] a refractive index of the seventh lens is n7, 1.50 ≤ n7 ≤ 1.68.

[0014] a dispersion coefficient of the first lens is v1, 50.0 ≤ v1 ≤ 70.0;

[0015] a dispersion coefficient of the second lens is v2, 18.0 ≤ v2 ≤ 26.0;

[0016] a dispersion coefficient of the third lens is v3, 30.0 ≤ v3 ≤ 50.0;

[0017] a dispersion coefficient of the fourth lens is v4, 50.0 ≤ v4 ≤ 70.0;

[0018] a dispersion coefficient of the fifth lens is v5, 18.0 ≤ v5 ≤ 26.0;

[0019] a dispersion coefficient of the sixth lens is v6, 50.0 ≤ v6 ≤ 70.0;

[0020] a dispersion coefficient of the seventh lens is v7, 50.0 ≤ v7 ≤ 70.0.

[0021] a power of the first lens is negative, an object side surface of the first lens is convex, and an image side surface of the first lens is concave;

[0022] a power of the second lens is negative, an object side surface of the second lens is concave, and an image side surface of the second lens is convex;

[0023] a power of the third lens is positive, an object side surface of the third lens is convex, and an image side surface of the third lens is concave;

[0024] a power of the fourth lens is positive, an object side surface of the fourth lens is convex, and an image side surface of the fourth lens is convex;

[0025] a power of the fifth lens is negative, an object side surface of the fifth lens is concave, and an image side surface of the fifth lens is convex;

[0026] a power of the sixth lens is positive, an object side surface of the sixth lens is convex, and an image side surface of the sixth lens is plane;

[0027] a power of the seventh lens is negative;

[0028] The fourth lens and the fifth lens are glued together.

[0029] In an embodiment, a distance between a vertex of an object side surface of the first lens and the image surface is TTL, and an effective focal length of the fixed focus optical system is EFL, wherein TTL≤13.5mm; and TTL / EFL≤3.42.

[0030] In an embodiment, an aperture value of the fixed focus optical lens is F, wherein F≤2.8.

[0031] In an embodiment, a diameter of the first lens is D, wherein D1<10mm.

[0032] In an embodiment, a height of the image surface is φ, wherein φ≤10.3mm.

[0033] In an embodiment, the fixed focus optical system further comprises a diaphragm, which is arranged between the third lens and the fourth lens.

[0034] In an embodiment, the fixed focus optical system further comprises:

[0035] A photosensitive chip is arranged at an image side of the seventh lens, and an end surface of the photosensitive chip towards an object side is the image surface; and

[0036] A filter is arranged between the seventh lens and the photosensitive chip.

[0037] The utility model discloses a technical scheme, the first lens and the third lens are glass spherical lens, and the glass lens can be good at resisting the problem of the deformation of the lens caused by heat, reduce the influence of temperature on the optical performance of the lens, keep the high precision of the lens for a long time, and the spherical lens processing is easy, can guarantee low processing cost, the assembly sensitivity is lower, improves the finished product yield, the aspheric lens has better curvature radius characteristics, has the advantages of improving the distortion and improving the astigmatism, after using the aspheric lens, can eliminate the aberration as far as possible when imaging, improves the edge picture quality, thereby improves the imaging quality of the lens, simultaneously, using the plastic aspheric lens can further reduce the manufacturing cost of the fixed focus optical system. Such setting, through the material combination of the multiple lenses of the fixed focus optical system, the face type distribution, and the reasonable control of the focal length of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens and the seventh lens, -8mm < f1 < -5mm, and -30mm < f2 < -20mm, and 4mm < f3 < 7mm, and 3mm < f4 < 6mm, and -9mm < f5 < -4mm, and 10mm < f6 < 25mm, and -25mm < f7 < -12mm, so that the fixed focus optical system can have very small chromatic aberration and other good performances under the premise of having large visual angle, high pixel and no thermalization. BRIEF DESCRIPTION OF DRAWINGS

[0038] In order to more clearly illustrate the technical scheme in the embodiments of the utility model or the prior art, the following will briefly introduce the drawings needed to be used in the embodiment or the prior art description, and obviously, the drawings in the following description are only some embodiments of the utility model, and for those skilled in the art, other drawings can be obtained according to the structure shown in these drawings without creating labor.

[0039] Figure 1 The structural schematic diagram of an embodiment of the fixed focus optical system provided by the utility model is shown in the figure.

[0040] Figure 2 The aspheric lens has better curvature radius characteristics, has the advantages of improving the distortion and improving the astigmatism, and the like. Figure 1 The sagittal aberration curve schematic diagram of the fixed focus optical system in the figure is shown in the figure.

[0041] Figure 3 The aspheric lens has better curvature radius characteristics, has the advantages of improving the distortion and improving the astigmatism, and the like. Figure 1 The sagittal aberration curve schematic diagram of the fixed focus optical system in the figure is shown in the figure.

[0042] Figure 4 The aspheric lens has better curvature radius characteristics, has the advantages of improving the distortion and improving the astigmatism, and the like. Figure 1 The ray aberration curve schematic diagram of the fixed focus optical system in the figure is shown in the figure.

[0043] Figure 5 The aspheric lens has better curvature radius characteristics, has the advantages of improving the distortion and improving the astigmatism, and the like. Figure 1 The field curvature distortion schematic diagram of the fixed focus optical system in the figure is shown in the figure.

[0044] Figure 6 For Figure 1 20℃ MTF diagram of the middle fixed focus optical system;

[0045] Figure 7 For Figure 1 -40℃ MTF diagram of the middle fixed focus optical system;

[0046] Figure 8 For Figure 1 90℃ MTF diagram of the middle fixed focus optical system.

[0047] BRIEF DESCRIPTION OF DRAWINGS

[0048] 100, fixed focus optical system; 1, first lens; 2, second lens; 3, third lens; 4, fourth lens; 5, fifth lens; 6, sixth lens; 7, seventh lens; 8, diaphragm; 9, photosensitive chip; 10, filter.

[0049] The implementation, functional features and advantages of the present application will be further described with reference to the accompanying drawings in conjunction with the embodiments. DETAILED DESCRIPTION

[0050] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0051] It should be noted that if the present application embodiments involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative positional relationship, movement condition, etc. between the components in a certain posture, and if the certain posture changes, the directional indications will also change accordingly.

[0052] In addition, if the description of "first", "second" and the like is involved in the embodiments of the present application, the description of "first", "second" and the like is only for the purpose of description, and cannot be understood as indicating or implying the relative importance of the indicated technical features or implicitly indicating the number of the indicated technical features. Therefore, the features limited by "first", "second" can be explicitly or implicitly included at least one of the features. In addition, if "and / or" or "and / or" appears throughout the text, it means that the three parallel schemes are included, for example, "A and / or B" includes A scheme, or B scheme, or A and B scheme. In addition, the technical solutions of each embodiment can be combined with each other, but it must be based on the realization of ordinary skilled in the art, when the combination of technical solutions appears contradictory or unachievable, it should be considered that the combination of technical solutions does not exist, and is not within the protection scope required by the present application.

[0053] The utility model provides a fixed focus optical system. Aims at improving the problem that the prior art optical system cannot meet large field angle, high definition and cannot adapt to large temperature difference change without virtual focus.

[0054] Please refer to Figure 1 In an embodiment of the present application, the fixed focus optical system 100 has a relative arrangement of the object side and the image side in the optical axis direction, the fixed focus optical system 100 includes first lens 1, second lens 2, third lens 3, fourth lens 4, fifth lens 5, sixth lens 6, seventh lens 7 and image plane arranged in sequence from the object side to the image side, the focal length of the first lens 1 is f1, the focal length of the second lens 2 is f2, the focal length of the third lens 3 is f3, the focal length of the fourth lens 4 is f4, the focal length of the fifth lens 5 is f5, the focal length of the sixth lens 6 is f6, the focal length of the seventh lens 7 is f7, the fixed focus optical system 100 meets the following conditions: -8mm < f1 < -5mm; and -30mm < f2 < -20mm; and 4mm < f3 < 7mm; and 3mm < f4 < 6mm; and -9mm < f5 < -4mm; and 10mm < f6 < 25mm; and -25mm < f7 < -12mm; the first lens 1 and the third lens 3 are glass spherical lenses, and the second lens 2, the fourth lens 4, the fifth lens 5, the sixth lens 6 and the seventh lens 7 are plastic aspherical lenses.

[0055] The utility model discloses a technical scheme, the first lens 1 and third lens 3 are glass spherical lens, and glass lens can be good to resist the problem of camera heat deformation, reduce the influence of temperature on camera optical performance, keep the high accuracy of camera for a long time, and spherical lens processing is easy, can guarantee low processing cost, and the assembly sensitivity is lower, improves the finished product yield, and aspherical lens has better curvature radius characteristics, has the advantage of improving distortion and improving astigmatism, aberration, after using aspherical lens, can eliminate the aberration that appears when imaging as far as possible, improves the edge quality, thereby improves the imaging quality of camera, simultaneously, using plastic aspherical lens can further reduce the manufacturing cost of fixed focus optical system 100. Such setting, through the material combination of the plurality of lenses of fixed focus optical system 100, face type distribution, and reasonable control the focal length of first lens 1, second lens 2, third lens 3, fourth lens 4, fifth lens 5, sixth lens 6 and seventh lens 7, -8mm < f1 < -5mm, and -30mm < f2 < -20mm, and 4mm < f3 < 7mm, and 3mm < f4 < 6mm, and -9mm < f5 < -4mm, and 10mm < f6 < 25mm, and -25mm < f7 < -12mm, so that fixed focus optical system 100 can also have very small chromatic aberration and other good performance under the premise of having large angle, high pixel, no thermalization.

[0056] It can be understood that, in the embodiment of the utility model, by setting the first lens 1 as a glass spherical lens, the influence of high temperature on the imaging of the first lens 1 on the object side of the fixed focus optical system 100 can be reduced, thereby ensuring the clear imaging of the fixed focus optical system 100.

[0057] It should be noted that the utility model does not limit the specific values of the focal length f1 of the first lens 1, the focal length f2 of the second lens 2, the focal length f3 of the third lens 3, the focal length f4 of the fourth lens 4, the focal length f5 of the fifth lens 5, the focal length f6 of the sixth lens 6 and the focal length f7 of the seventh lens 7, and the focal length f1 of the first lens 1, the focal length f2 of the second lens 2, the focal length f3 of the third lens 3, the focal length f4 of the fourth lens 4, the focal length f5 of the fifth lens 5, the focal length f6 of the sixth lens 6 and the focal length f7 of the seventh lens 7 can be set to any value within the corresponding range, and the utility model does not limit this. In actual setting, it can be selected according to requirements.

[0058] In addition, in the embodiment of the utility model, the refractive index of the first lens 1 is n1, 1.50≤n1≤1.75, the refractive index of the second lens 2 is n2, 1.60≤n2≤1.70, the refractive index of the third lens 3 is n3, 1.75≤n3≤1.95, the refractive index of the fourth lens 4 is n4, 1.50≤n4≤1.60, the refractive index of the fifth lens 5 is n5, 1.60≤n5≤1.70, the refractive index of the sixth lens 6 is n6, 1.50≤n6≤1.60, and the refractive index of the seventh lens 7 is n7, 1.50≤n7≤1.68.

[0059] It can be understood that the utility model also does not limit the value of the refractive index n1 of the first lens 1, the refractive index n2 of the second lens 2, the refractive index n3 of the third lens 3, the refractive index n4 of the fourth lens 4, the refractive index n5 of the fifth lens 5, the refractive index n6 of the sixth lens 6 and the refractive index n7 of the seventh lens 7.

[0060] In the embodiment of the utility model, the refractive index n1 of the first lens 1, the refractive index n2 of the second lens 2, the refractive index n3 of the third lens 3, the refractive index n4 of the fourth lens 4, the refractive index n5 of the fifth lens 5, the refractive index n6 of the sixth lens 6 and the refractive index n7 of the seventh lens 7 can be set to any value within the corresponding range, and the utility model does not limit this, and in actual setting, it can be selected according to requirements.

[0061] In the further embodiment of the utility model, the dispersion coefficient of the first lens 1 is v1, 50.0≤v1≤70.0, the dispersion coefficient of the second lens 2 is v2, 18.0≤v2≤26.0, the dispersion coefficient of the third lens 3 is v3, 30.0≤v3≤50.0, the dispersion coefficient of the fourth lens 4 is v4, 50.0≤v4≤70.0, the dispersion coefficient of the fifth lens 5 is v5, 18.0≤v5≤26.0, the dispersion coefficient of the sixth lens 6 is v6, 50.0≤v6≤70.0, and the dispersion coefficient of the seventh lens 7 is v7, 50.0≤v7≤70.0.

[0062] Similarly, the utility model also does not limit the value of the dispersion coefficient v1 of the first lens 1, the dispersion coefficient v2 of the second lens 2, the dispersion coefficient v3 of the third lens 3, the dispersion coefficient v4 of the fourth lens 4, the dispersion coefficient v5 of the fifth lens 5, the dispersion coefficient v6 of the sixth lens 6 and the dispersion coefficient v7 of the seventh lens 7.

[0063] In the actual setting, the dispersion coefficient v1 of the first lens 1, the dispersion coefficient v2 of the second lens 2, the dispersion coefficient v3 of the third lens 3, the dispersion coefficient v4 of the fourth lens 4, the dispersion coefficient v5 of the fifth lens 5, the dispersion coefficient v6 of the sixth lens 6 and the dispersion coefficient v7 of the seventh lens 7 can be set to any value in the corresponding range, which can be selected as required, and the utility model does not limit this.

[0064] In the further embodiment of the utility model, the focal power of the first lens 1 is negative, the object side of the first lens 1 is convex, and the image side is concave; the focal power of the second lens 2 is negative, the object side of the second lens 2 is concave, and the image side is convex; the focal power of the third lens 3 is positive, the object side of the third lens 3 is convex, and the image side is concave; the focal power of the fourth lens 4 is positive, the object side of the fourth lens 4 is convex, and the image side is convex; the focal power of the fifth lens 5 is negative, the object side of the fifth lens 5 is concave, and the image side is convex; the focal power of the sixth lens 6 is positive, the object side of the sixth lens 6 is convex, and the image side is flat; and the focal power of the seventh lens 7 is negative. By the cooperation of the focal power and shape of the seven lenses, the compactness and lightness can be realized, the light path can be well controlled, more light can be introduced, and the structure of the fixed focus optical system 100 is more compact.

[0065] In this embodiment, by setting the first lens 1 as a lens with negative focal power, the fixed focus optical system 100 can collect light, thereby effectively increasing the field of view of the fixed focus optical system 100.

[0066] Meanwhile, the third lens 3 is set as a lens with positive focal power, so that the third lens 3 bears a large focal power of the fixed focus optical system 100, so that the chromatic aberration of the fixed focus optical system 100 can be better corrected, and the volume of the fixed focus optical system 100 can be compressed.

[0067] It should be further noted that in this embodiment, the fourth lens 4 and the fifth lens 5 are glued together, so that the light energy loss can be further reduced, the imaging clarity can be increased, the scale surface can be protected, the processing flow can be optimized to meet the design requirements, and the optical components can improve the image quality of the fixed focus optical system 100 by reasonably using the glued parts.

[0068] In still another embodiment of the present application, the distance between the vertex of the object side of the first lens 1 and the image plane is TTL, and the effective focal length of the fixed focus optical system 100 is EFL, wherein TTL≤13.5mm; and TTL / EFL≤3.42. In this way, the total length of the lens of the fixed focus optical system 100 is controlled within 13.5mm, so as to ensure the compactness and small volume of the fixed focus optical system 100.

[0069] In still another embodiment of the present application, the diameter of the first lens 1 is D, wherein D1<10mm. In this way, the aperture of the fixed focus optical system 100 can be avoided to be too large, so as to meet the installation space requirement of the final product.

[0070] In addition, in an embodiment of the present application, the aperture value of the fixed focus optical lens is F, wherein F≤2.8. In this way, the fixed focus optical system 100 has a large light flux, so as to have excellent picture brightness, thereby further improving the imaging quality of the fixed focus optical system 100.

[0071] It can be understood that the present application does not limit the specific value of the aperture value F of the fixed focus optical system 100. In the embodiment of the present application, the aperture value F of the fixed focus optical system 100 can be set to any value within the range, and the present application does not limit this. In actual setting, the value can be selected according to the requirement.

[0072] It should be further pointed out that in another embodiment of the present application, the height of the image plane is φ, and φ≤10.3mm. In this way, in combination with the large aperture value of the fixed focus optical lens, the fixed focus optical system 100 can also clearly image in weak light, and through the mutual combination and reasonable distribution of light focal length of different lenses, the fixed focus optical system 100 has good performances such as large view angle, high pixel, and very good athermalization, and has a wider field of view and obtains more sufficient data information.

[0073] In order to enable the fixed focus optical system 100 to adjust the light flux according to the actual situation, in an embodiment of the present application, the fixed focus optical system 100 further comprises a diaphragm 8, and the diaphragm 8 is arranged between the third lens 3 and the fourth lens 4. The diaphragm 8 limits the light beam aperture on the optical axis, and blocks part of the light, thereby reducing the light spot and improving the image contrast, so as to improve the imaging quality of the fixed focus optical system 100.

[0074] At the same time, since the diaphragm 8 is arranged on the side of the cemented lens formed by the fourth lens 4 and the fifth lens 5 towards the object side, in this way, the chromatic aberration of the fixed focus optical system 100 can be better corrected, and the volume of the fixed focus optical system 100 can be compressed.

[0075] It should be further explained that the fixed focus optical system 100 further comprises a photosensitive chip 9 and a filter 10, the photosensitive chip 9 is spaced apart from the image side of the seventh lens 7, the end face of the photosensitive chip 9 towards the object side is the image plane, and the filter 10 is arranged between the seventh lens 7 and the photosensitive chip 9. The arrangement of the filter 10 can protect the photosensitive chip 9 while filtering out stray light, thereby further improving the imaging quality.

[0076] In a specific embodiment of the present application, the object side of the first lens 1 is S1, and the image side is S2; the object side of the second lens 2 is S3, and the image side is S4; the object side of the third lens 3 is S5, and the image side is S6; the object side of the fourth lens 4 is S8, and the image side is S9; the object side of the fifth lens 5 is S9, and the image side is S10; the object side of the sixth lens 6 is S11, and the image side is S12; and the object side of the seventh lens 7 is S13, and the image side is S14.

[0077] In this embodiment, the focal length f of the fixed focus optical system 100 is 3.89mm, the aperture value F is 2.8, the image plane diameter is 10.3mm, and the diagonal field of view angle is 155°.

[0078] It should be noted that in this embodiment, the basic parameter table of the lens surface type, the radius of curvature, the thickness, the refractive index, the dispersion coefficient and the half diameter of the fixed focus optical system 100 is shown in Table 1:

[0079] Table 1

[0080]

[0081]

[0082] It can be understood that in this embodiment, the first lens 1 and the third lens 3 are glass spherical lenses, and the spherical lenses are arranged to reduce the cost under the premise of ensuring the image quality and reliability, the assembly sensitivity is low, and the yield of finished products is improved.

[0083] Correspondingly, in this embodiment, the second lens 2, the fourth lens 4, the fifth lens 5, the sixth lens 6 and the seventh lens 7 are plastic aspherical lenses. The aspherical lens has the following characteristics: from the center of the lens to the periphery of the lens, the curvature is continuously changed, which is different from the spherical lens with constant curvature from the center of the lens to the periphery of the lens. The aspherical lens has better radius of curvature characteristics, has the advantages of improving distortion aberration and improving astigmatism aberration, and after the aspherical lens is adopted, the aberration that occurs during imaging can be eliminated as much as possible, thereby improving the imaging quality of the lens.

[0084] It should be noted that in the embodiment, the object side of the sixth lens 6 is convex, and the image side is flat. However, since the sixth lens 6 is an aspherical lens, according to the definition of the aspherical lens, the radius of curvature of the second lens 22 can be positive in the embodiment. The same applies to the seventh lens 7.

[0085] Further, in the embodiment, the aspherical surface shape of the aspherical lens satisfies the following conditions:

[0086]

[0087] wherein z represents the axial height of the aspherical Z direction; y represents the height of the aspherical surface; c represents the curvature of the fitting sphere, which is the reciprocal of the radius of curvature in value; k represents the conic coefficient; and the 4th, 6th, 8th, 10th, 12th, 14th and 16th order terms represent the high-order aspherical coefficients, respectively.

[0088] In the embodiment, the high-order coefficients of each aspherical mirror surface are known from Table 2 below:

[0089] Table 2

[0090] Surface No. K 4th order term 6th order term 8th order term 10th order term 12th order term 14th order term 16th order term 3 -0.644 -1.28E-03 3.82E-04 -1.76E-05 -3.44E-06 1.02E-07 5.18E-08 -4.08E-09 4 0.806 -3.83E-04 4.68E-04 -5.93E-05 1.80E-06 4.58E-07 -1.14E-07 8.29E-09 8 -0.531 -5.02E-03 7.37E-03 -1.64E-02 1.52E-02 -5.06E-03 -1.94E-04 0.00E+00 9 -0.745 -1.72E-02 4.91E-03 5.80E-04 -2.86E-03 2.01E-04 2.31E-04 0.00E+00 10 21.821 -6.75E-03 3.10E-03 -1.15E-03 1.99E-04 -2.29E-05 2.08E-07 0.00E+00 11 1.489 -3.83E-03 -8.36E-04 -1.04E-04 3.68E-05 -4.93E-06 1.43E-07 -3.28E-09 12 30.447 4.35E-03 -1.33E-03 8.65E-06 2.15E-06 -2.20E-07 -3.71E-08 2.60E-09 13 -1.297 -2.44E-02 2.33E-03 -1.51E-04 -3.10E-06 5.64E-08 3.91E-08 -2.43E-09 14 -4.294 -1.17E-02 1.13E-03 -6.92E-05 6.59E-07 8.32E-08 -6.59E-10 -8.48E-11

[0091] In this way, by reasonably distributing the lens focal power, adjusting the glass shape and material matching, effectively correcting the chromatic aberration and secondary spectrum, and mutually compensating and offsetting the spherical aberration, coma, astigmatism and the like on each lens, a clear imaging effect is achieved, and the optimal correction of high-order aberration and chromatic aberration is achieved.

[0092] In addition, in the embodiment, the spherical aberration curve of the fixed focus optical system 100 is as shown in Figure 2 ; the sagittal chromatic aberration curve of the fixed focus optical system 100 is as shown in Figure 3 ; the ray aberration curve of the fixed focus optical system 100 is as shown in Figure 4 ; and the field curvature distortion of the fixed focus optical system 100 is as shown in Figure 5 .

[0093] It should be noted that Table 2 is a design value of the aspherical coefficients of the lenses in the fixed focus optical system 100 in the embodiment, and the specific numerical value of the aspherical coefficient design value can be adjusted according to the product requirements, and the utility model does not limit this.

[0094] In the embodiment, the 20℃ MTF curve of the fixed focus optical system 100 is as shown in Figure 6 ; the -40℃ MTF curve of the fixed focus optical system 100 is as shown in Figure 7 ; and the 90℃ MTF curve of the fixed focus optical system 100 is as shown in Figure 8As shown, in the present embodiment, it is determined that the fixed focus optical system 100 can adapt to large temperature difference changes without defocusing.

[0095] The above merely illustrates the embodiments of the present application, and does not limit the patent scope of the present application, and any equivalent structural transformation, direct / indirect application in other related technical fields, or the like, made by using the present application specification and drawings, are included in the patent protection scope of the present application.

Claims

1. A fixed-focus optical system, characterized in that, The fixed-focus optical system has an object side and an image side that are oppositely arranged in the optical axis direction. The fixed-focus optical system includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, and an image plane that are arranged in sequence from the object side to the image side. The focal length of the first lens is f1, the focal length of the second lens is f2, the focal length of the third lens is f3, the focal length of the fourth lens is f4, the focal length of the fifth lens is f5, the focal length of the sixth lens is f6, and the focal length of the seventh lens is f7. The fixed-focus optical system satisfies the following conditions: -8 mm < f1 < -5 mm; and -30 mm < f2 < -20 mm; and 4 mm < f3 < 7 mm; and 3 mm < f4 < 6 mm; and -9 mm < f5 < -4 mm; and 10 mm < f6 < 25 mm; and -25 mm < f7 < -12 mm; Among them, the first lens and the third lens are glass spherical lenses, and the second lens, the fourth lens, the fifth lens, the sixth lens, and the seventh lens are plastic aspherical lenses.

2. The fixed-focus optical system as described in claim 1, characterized in that, The refractive index of the first lens is n1, 1.50 ≤ n1 ≤ 1.75; The refractive index of the second lens is n2, 1.60 ≤ n2 ≤ 1.70; The refractive index of the third lens is n3, 1.75 ≤ n3 ≤ 1.95; The refractive index of the fourth lens is n4, 1.50 ≤ n4 ≤ 1.60; The refractive index of the fifth lens is n5, 1.60 ≤ n5 ≤ 1.70; The refractive index of the sixth lens is n6, 1.50 ≤ n6 ≤ 1.60; The refractive index of the seventh lens is n7, 1.50 ≤ n7 ≤ 1.

68.

3. The fixed-focus optical system as described in claim 1, characterized in that, The dispersion coefficient of the first lens is v1, 50.0 ≤ v1 ≤ 70.0; The dispersion coefficient of the second lens is v2, 18.0 ≤ v2 ≤ 26.0; The dispersion coefficient of the third lens is v3, 30.0 ≤ v3 ≤ 50.0; The dispersion coefficient of the fourth lens is v4, 50.0 ≤ v4 ≤ 70.0; The dispersion coefficient of the fifth lens is v5, 18.0 ≤ v5 ≤ 26.0; The dispersion coefficient of the sixth lens is v6, 50.0 ≤ v6 ≤ 70.0; The dispersion coefficient of the seventh lens is v7, 50.0 ≤ v7 ≤ 70.

0.

4. The fixed-focus optical system as described in claim 1, characterized in that, The optical power of the first lens is negative. The object side surface of the first lens is convex, and the image side surface is concave; The optical power of the second lens is negative. The object side surface of the second lens is concave, and the image side surface is convex; The optical power of the third lens is positive. The object side surface of the third lens is convex, and the image side surface is concave; The optical power of the fourth lens is positive. The object side surface of the fourth lens is convex, and the image side surface is convex; The optical power of the fifth lens is negative. The object side surface of the fifth lens is concave, and the image side surface is convex; The optical power of the sixth lens is positive. The object side surface of the sixth lens is convex, and the image side surface is flat; The optical power of the seventh lens is negative; Among them, the fourth lens and the fifth lens are adhesively connected.

5. The fixed-focus optical system as described in claim 1, characterized in that, The distance between the vertex of the object side of the first lens and the image plane is TTL, and the effective focal length of the fixed-focus optical system is EFL, wherein TTL≤13.5mm; and TTL / EFL≤3.

42.

6. The fixed-focus optical system as described in claim 1, characterized in that, The aperture value of the fixed-focus optical lens is F, where F≤2.

8.

7. The fixed-focus optical system as described in claim 1, characterized in that, The diameter of the first lens is D, where D1 < 10 mm.

8. The fixed-focus optical system as described in claim 1, characterized in that, The height of the image plane is φ, where φ ≤ 10.3 mm.

9. The fixed-focus optical system as described in claim 1, characterized in that, The fixed-focus optical system also includes an aperture stop, which is located between the third lens and the fourth lens.

10. The fixed-focus optical system as described in claim 1, characterized in that, The fixed-focus optical system also includes: A photosensitive chip is spaced apart on the image side of the seventh lens, and the end face of the photosensitive chip facing the object side is the image plane; and, A filter is disposed between the seventh lens and the photosensitive chip.

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