Prime lens

Abstract

The utility model discloses a prime lens. The prime lens sequentially comprises a first lens with negative focal power, a second lens with negative focal power, a third lens with positive focal power, a fourth lens with positive focal power, a fifth lens with negative focal power, a sixth lens with positive focal power, a seventh lens and an eighth lens from the object side to the image side along the optical axis. The object-side surface of the first lens is a convex surface, and the image-side surface is a concave surface. The object side surface of the second lens is a concave surface, and the image side surface is a convex surface; the object side surface of the third lens is a convex surface; the object side surface of the fourth lens is a convex surface, and the image side surface is a convex surface; the object side surface of the fifth lens is a concave surface; the object side surface of the sixth lens is a convex surface; the object side surface of the eighth lens is a convex surface; the fourth lens and the fifth lens form a bonding lens, and the optical total length TTL of the prime lens, the half H of the diagonal length of the imaging surface of the prime lens and the total effective focal length F of the prime lens meet the condition that TTL * H / F is larger than or equal to 12.38 and smaller than or equal to 13.70.

Description

Technical Field

[0001] The present application relates to the field of optical devices, and in particular to a fixed-focus lens. Background Art

[0002] With the rapid development of modern photography and video technology, fixed-focus lenses are widely used in video conferencing, security monitoring, sports photography and other video lens fields. Customers' demands for lenses are gradually tending towards large image area, low distortion and high resolution. To achieve large image area, low distortion and high resolution for video conferencing lenses, it is generally necessary to increase the number of lenses to balance system performance. At this time, the lens may have the problem of being too long and too large in size. Utility Model Content

[0003] The present application provides such a fixed-focus lens, which includes, in order from the object side to the image side along the optical axis: a first lens with negative optical power, a second lens with negative optical power, a third lens with positive optical power, a fourth lens with positive optical power, a fifth lens with negative optical power, a sixth lens with positive optical power, and at least one seventh lens and an eighth lens with positive optical power; the object side surface of the first lens is a convex surface, and the image side surface is a concave surface; the object side surface of the second lens is a concave surface, and the image side surface is a convex surface; the object side surface of the third lens is a convex surface; The object side surface of the fourth lens is convex, and the image side surface is convex; the object side surface of the fifth lens is concave; the object side surface of the sixth lens is convex; the object side surface of the eighth lens is convex; the fourth lens and the fifth lens form a cemented lens, and the total optical length TTL of the fixed-focus lens, half of the diagonal length H of the imaging surface of the fixed-focus lens and the total effective focal length F of the fixed-focus lens satisfy: 12.38≤TTL*H / F≤13.70; the effective focal length F3 of the third lens and the total effective focal length F of the fixed-focus lens satisfy: 0.8≤F3 / F≤1.78.

[0004] According to an exemplary embodiment of the present application, the total optical length TTL of the fixed-focus lens and half of the diagonal length H of the imaging surface of the fixed-focus lens satisfy: 5.5≤TTL / H≤6.12.

[0005] According to an exemplary embodiment of the present application, the total optical length TTL of the fixed-focus lens and the total effective focal length F of the fixed-focus lens satisfy: 2.76≤TTL / F≤3.1.

[0006] According to an exemplary embodiment of the present application, the larger optical full aperture value D1 of the object side surface and the image side surface of the first lens and the total optical length TTL of the fixed focus lens satisfy: 0.26≤D1 / TTL≤0.35.

[0007] According to an exemplary embodiment of the present application, a curvature radius R22 of the image-side surface of the second lens and a curvature radius R31 of the object-side surface of the third lens satisfy: -0.6≤(R22+R31) / (R22-R31)≤0.3.

[0008] According to an exemplary embodiment of the present application, a curvature radius R21 of the object side surface of the second lens, a curvature radius R22 of the image side surface of the second lens, and a total effective focal length F of the fixed focus lens satisfy: -2.4≤(R21+R22) / F≤-0.75.

[0009] According to an exemplary embodiment of the present application, an effective focal length F4 of the fourth lens and a curvature radius R42 of the image-side surface of the fourth lens satisfy: -1.83≤F4 / R42≤-0.95.

[0010] According to an exemplary embodiment of the present application, a curvature radius R81 of the image-side surface of the eighth lens and a curvature radius R82 of the object-side surface of the eighth lens satisfy: 0.6≤|R82 / R81|≤2.3.

[0011] According to an exemplary embodiment of the present application, the fixed-focus lens further includes a stop, and the effective combined focal length Fa of the front lens group of the stop and the total effective focal length F of the fixed-focus lens satisfy: 0.9≤Fa / F≤8.2.

[0012] According to an exemplary embodiment of the present application, the Abbe number of the material used for the fourth lens, the Abbe number of the material used for the fifth lens, and the combined effective focal length F45 of the fourth lens and the fifth lens satisfy: 0.9≤|(Vd4-Vd5) / F45|≤4.5.

[0013] According to an exemplary embodiment of the present application, the combined effective focal length F45 of the fourth lens and the fifth lens and the total effective focal length F of the fixed focus lens satisfy: -4.5≤F45 / F≤2.

[0014] According to an exemplary embodiment of the present application, a combined effective focal length F67 of the sixth lens and the seventh lens and a total effective focal length F of the fixed focus lens satisfy: 1≤|F67 / F|≤3.9.

[0015] According to an exemplary embodiment of the present application, one or more of the first to eighth lenses are glass lenses and one or more are plastic lenses.

[0016] According to an exemplary embodiment of the present application, the sixth lens and the seventh lens are a cemented lens.

[0017] The fixed-focus lens provided in the present application has 8 lenses, and the total optical length TTL of the fixed-focus lens, half the diagonal length H of the imaging surface IMG of the fixed-focus lens, and the total effective focal length F of the fixed-focus lens satisfy: 12.38≤TTL*H / F≤13.70. When this relationship is satisfied, the market demand for miniaturization of the fixed-focus lens can be met while the fixed-focus lens is adapted to a large-size imaging surface IMG (imaging chip), so that the fixed-focus lens can simultaneously meet the market demand for large target surface and miniaturization; the effective focal length F3 of the third lens and the total effective focal length F of the fixed-focus lens satisfy: 0.8≤F3 / F≤1.78. Reasonable setting of the effective focal length of the third lens can effectively collect and compress the incident light in the front, so that the light can smoothly transition to the rear optical system, reduce the generation of aberrations, and thus improve the imaging quality of the lens. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Other features, objects and advantages of the present application will become more apparent by reading the detailed description of non-limiting embodiments made with reference to the following drawings, in which:

[0019] Figure 1 A schematic structural diagram of a fixed-focus lens according to Embodiment 1 of the present application is shown;

[0020] Figure 2 shows a distortion curve of a fixed-focus lens according to Example 1 of the present application;

[0021] Figure 3 A schematic structural diagram of a fixed-focus lens according to Embodiment 2 of the present application is shown;

[0022] Figure 4 shows a distortion curve of a fixed-focus lens according to Example 2 of the present application;

[0023] Figure 5 A schematic structural diagram of a fixed-focus lens according to Embodiment 3 of the present application is shown;

[0024] Figure 6 shows a distortion curve of a fixed-focus lens according to Example 3 of the present application;

[0025] Figure 7 A schematic structural diagram of a fixed-focus lens according to Embodiment 4 of the present application is shown; and

[0026] Figure 8 The distortion curve of the fixed-focus lens according to Example 4 of the present application is shown. DETAILED DESCRIPTION

[0027] In order to better understand the present application, a more detailed description will be made of various aspects of the present application with reference to the accompanying drawings. It should be understood that these detailed descriptions are only descriptions of exemplary embodiments of the present application, and do not limit the scope of the present application in any way. Throughout the specification, the same figure numerals refer to the same elements.

[0028] It should be noted that in this specification, the expressions of first, second, third, etc. are only used to distinguish one feature from another feature, and do not represent any limitation on the features. Therefore, without departing from the teaching of the present application, the first lens discussed below may also be referred to as the second lens or the third lens.

[0029] In the drawings, the thickness, size and shape of the lenses have been slightly exaggerated for ease of illustration. Specifically, the shapes of the spherical or aspherical surfaces shown in the drawings are shown by way of example. That is, the shapes of the spherical or aspherical surfaces are not limited to the shapes of the spherical or aspherical surfaces shown in the drawings. The drawings are for illustration only and are not drawn strictly to scale.

[0030] In this article, the paraxial region refers to the region near the optical axis. If the lens surface is convex and the position of the convex surface is not defined, it means that the lens surface is convex at least in the paraxial region; if the lens surface is concave and the position of the concave surface is not defined, it means that the lens surface is concave at least in the paraxial region. The surface of each lens closest to the object is called the object side of the lens, and the surface of each lens closest to the image plane is called the image side of the lens.

[0031] It should also be understood that the terms "including" and / or "having", when used in this specification, indicate the presence of the stated features, elements and / or components, but do not exclude the presence or addition of one or more other features, elements, components and / or combinations thereof. In addition, when describing the embodiments of the present application, the term "may" is used to mean "one or more embodiments of the present application". And, the term "exemplary" is intended to refer to an example or illustration.

[0032] Unless otherwise defined, all terms (including technical terms and scientific terms) used in this article have the same meaning as those commonly understood by ordinary technicians in the field to which this application belongs. It should also be understood that terms (such as terms defined in commonly used dictionaries) should be interpreted as having the same meaning as their meaning in the context of the relevant technology, and will not be interpreted in an idealized or overly formal sense unless explicitly defined in this article.

[0033] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0034] refer to Figure 1 , Figure 3 , Figure 5 and Figure 7 In one aspect, the present application provides a fixed-focus lens, which includes a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, a sixth lens L6, a seventh lens L7 and an eighth lens L8 in sequence from the object side to the image side along the optical axis.

[0035] In an exemplary embodiment, the first lens L1 has negative optical power, a convex object-side surface, a concave image-side surface, and a meniscus shape with the convex surface facing the object side, which can effectively collect incident light with a large field of view angle, achieving a maximum field of view angle FOV>55° of the fixed-focus lens.

[0036] In an exemplary embodiment, the second lens L2 has negative optical power, a concave object-side surface, a convex image-side surface, and a meniscus shape with the convex surface facing the image side, which can preliminarily correct the astigmatism of the optical system while effectively controlling the trend of light to achieve a larger aperture.

[0037] In an exemplary embodiment, the third lens L3 has positive refractive power, and the object side surface is convex, and the image side surface can be convex or concave, which can effectively collect and compress the incident light on the object side and make the light smoothly transition to the optical system on the image side.

[0038] In an exemplary embodiment, the fourth lens L4 has positive refractive power, the object side surface is convex, and the image side surface is convex. The biconvex structure is beneficial for lowering the incident angle of light after the light passes through the aperture, so that more light enters the optical system on the image side, thereby improving the illumination of the optical system.

[0039] In an exemplary embodiment, the fifth lens L5 has a negative optical power, and the object side surface is a concave surface. In some cases, the fifth lens L5 and the fourth lens L4 are combined into a cemented lens, which is beneficial to correcting chromatic aberration and balancing various aberrations, improving resolution, and can effectively reduce tolerance sensitivity, improve the yield of the lens, and help ensure the imaging quality of the optical system.

[0040] In an exemplary embodiment, the sixth lens L6 has positive refractive power, and the object side surface is convex, and the image side surface can be convex or concave, which can make the light transition smoothly, help correct the axial aberration, and improve the imaging quality of the optical lens.

[0041] In an exemplary embodiment, the seventh lens L7 may have a focal power, and the seventh lens L7 may have a positive focal power or a negative focal power. By properly setting the focal power and shape of the seventh lens L7, the light trend is effectively controlled, the light angle is raised, and the imaging height can match a large-sized chip, thereby achieving a large target surface.

[0042] In an exemplary embodiment, the sixth lens L6 and the seventh lens L7 are cemented lenses, which are beneficial for correcting chromatic aberration and balancing various aberrations, improving resolution, and can effectively reduce tolerance sensitivity, thereby improving the imaging quality of the optical system; in addition, it can also reduce the assembly sensitivity of the fixed-focus lens, thereby reducing the difficulty of the processing technology of the fixed-focus lens and improving the assembly yield of the fixed-focus lens.

[0043] In an exemplary embodiment, the eighth lens L8 may have a focal power, and the eighth lens L8 may have a positive focal power or a negative focal power. The object side surface of the eighth lens L8 is a convex surface, and the surface type of the eighth lens L8 is set to be an aspherical surface. Through the design of the aspherical recurve, the distortion of the edge field of view can be effectively corrected, so that the optical distortion is ≤|-5%|, and low distortion of the optical system is achieved, while being beneficial to improving the imaging quality.

[0044] In exemplary embodiments, at least one of seventh lens L7 and eighth lens L8 has positive refractive power.

[0045] In the exemplary embodiment, the shapes of the image-side surfaces of the third lens L3 , the fifth lens L5 , the sixth lens L6 , and the eighth lens L8 are not limited.

[0046] In an exemplary embodiment, the fixed focus lens may further include an aperture. The aperture may be located between the third lens L3 and the fourth lens L4, in which case the light entering the optical system may be effectively converged, the total length of the optical system may be shortened, and the maximum aperture of the optical system may be reduced, which is conducive to realizing a miniaturized design.

[0047] In an exemplary embodiment, the total optical length TTL of the fixed-focus lens, half the diagonal length H of the imaging surface IMG of the fixed-focus lens, and the total effective focal length F of the fixed-focus lens satisfy: 12.38≤TTL*H / F≤13.70. This relationship reflects the constraints of the characteristics of the target surface size and volume size of the optical lens. When this relationship is satisfied, the fixed-focus lens can be adapted to a large-sized imaging surface IMG (imaging chip) and meet the market demand for miniaturization of fixed-focus lenses, so that the fixed-focus lens can meet the market demand for large target surfaces and miniaturization at the same time. Among them, the total optical length TTL of the fixed-focus lens, half the diagonal length H of the imaging surface IMG of the fixed-focus lens, and the total effective focal length F of the fixed-focus lens are all in millimeters (mm).

[0048] In an exemplary embodiment, the effective focal length F3 of the third lens L3 and the total effective focal length F of the fixed-focus lens satisfy: 0.8≤F3 / F≤1.78. Reasonable setting of the effective focal length of the third lens can effectively collect and compress the incident light in the front, so that the light can smoothly transition to the rear optical system, reduce the generation of aberrations, and thus improve the imaging quality of the lens.

[0049] In an exemplary embodiment, the total optical length TTL of the fixed-focus lens and half the diagonal length H of the imaging surface IMG of the fixed-focus lens satisfy: 5.5≤TTL / H≤6.12. Under a certain image height of the optical system, the ratio of the image height to the focal length of the optical system is controlled to limit the total length of the optical system to a smaller value, so as to achieve miniaturization.

[0050] In an exemplary embodiment, the total optical length TTL of the fixed-focus lens and the total effective focal length F of the fixed-focus lens satisfy: 2.76≤TTL / F≤3.1. Under a certain total effective focal length of the optical system, the ratio of the total optical length of the system to the total effective focal length is controlled to limit the optical system to have a smaller total optical length to achieve miniaturization.

[0051] In an exemplary embodiment, the larger optical full aperture value D1 of the object side and the image side of the first lens L1 and the total optical length TTL of the fixed focus lens satisfy: 0.26≤D1 / TTL≤0.35. By controlling the ratio of the maximum optical full aperture value of the first lens L1 to the total optical length, the volume of the lens is limited to achieve miniaturization.

[0052] In an exemplary embodiment, the curvature radius R22 of the image side surface of the second lens L2 and the curvature radius R31 of the object side surface of the third lens L3 satisfy: -0.6≤(R22+R31) / (R22-R31)≤0.3. Reasonable configuration of the values ​​of the curvature radii of the image side surface of the second lens L2 and the object side surface of the third lens L3 effectively controls the direction of light, is conducive to correcting astigmatism and field curvature, and thus improves the resolution quality.

[0053] In an exemplary embodiment, the curvature radius R21 of the object side surface of the second lens L2, the curvature radius R22 of the image side surface of the second lens L2, and the total effective focal length F of the fixed focus lens satisfy: -2.4≤(R21+R22) / F≤-0.75. Reasonable configuration of the curvature radii of the object side surface and the image side surface of the second lens L2 is conducive to correcting astigmatism and improving the resolution of the optical system.

[0054] In an exemplary embodiment, the effective focal length F4 of the fourth lens L4 and the curvature radius R42 of the image side surface of the fourth lens L4 satisfy: -1.83≤F4 / R42≤-0.95. Reasonable configuration of the effective focal length of the fourth lens L4 and the curvature radius ratio of the image side surface of the fourth lens L4 is conducive to correcting astigmatism and spherical aberration, and improving the resolution of the optical system.

[0055] In an exemplary embodiment, the curvature radius R81 of the image side surface of the eighth lens L8 and the curvature radius R82 of the object side surface of the eighth lens L8 satisfy: 0.6≤|R82 / R81|≤2.3. Reasonable control of the ratio of the curvature radius of the object side surface and the image side surface of the eighth lens L8 and reasonable setting of the shape of the eighth lens L8 are conducive to better correction of distortion, making the optical distortion ≤|-5%|, and realizing low distortion of the optical system.

[0056] In an exemplary embodiment, when the fixed-focus lens further includes an aperture, the effective combined focal length Fa of the front lens group of the aperture and the total effective focal length F of the fixed-focus lens satisfy: 0.9≤Fa / F≤8.2. Reasonable allocation of the effective combined focal length of the front lens group of the aperture is conducive to better correction of distortion, making the optical distortion ≤|-5%|, and achieving low distortion of the optical system. The front lens group includes a first lens L1, a second lens L2, and a third lens L3.

[0057] In an exemplary embodiment, the Abbe number of the material used for the fourth lens L4, the Abbe number of the material used for the fifth lens L5, and the combined effective focal length F45 of the fourth lens L4 and the fifth lens L5 satisfy: 0.9≤|(Vd4-Vd5) / F45|≤4.5. The difference in the Abbe numbers of the fourth lens L4 and the fifth lens L5 and the ratio of the combined effective focal lengths of the fourth lens L4 and the fifth lens L5 are reasonably set. When the above relationship is satisfied, the chromatic aberration of the optical system can be effectively corrected, the authenticity of the colors can be restored, and the imaging quality can be improved.

[0058] In an exemplary embodiment, the combined effective focal length F45 of the fourth lens L4 and the fifth lens L5 and the total effective focal length F of the fixed-focus lens satisfy: -4.5≤F45 / F≤2. Reasonable configuration of the combined effective focal length of the fourth lens L4 and the fifth lens L5 helps to control the trend of light, so that the light smoothly transitions to the rear of the optical system after passing through the aperture, which is conducive to balancing various aberrations, improving the resolution of the lens, and at the same time helps to reduce tolerance sensitivity and improve the production yield of the lens.

[0059] In an exemplary embodiment, the combined effective focal length F67 of the sixth lens L6 and the seventh lens L7 and the total effective focal length F of the fixed focus lens satisfy: 1≤|F67 / F|≤3.9. Reasonable configuration of the combined effective focal length of the sixth lens L6 and the seventh lens L7 allows light to smoothly transition to the rear optical system, which is beneficial to balancing various aberrations, improving the resolution of the lens, and at the same time helps to reduce tolerance sensitivity and improve the production yield of the lens.

[0060] In an exemplary embodiment, the first lens L1 to the eighth lens L8 include glass lenses and plastic lenses. The fixed-focus lens uses a glass-plastic hybrid lens, which is conducive to reducing the cost of the optical system and balancing the high and low temperature performance of the fixed-focus lens, achieving high imaging quality in the range of -20°C to 60°C; one or more lenses use glass lenses, which is conducive to correcting the chromatic aberration of the optical system and better restoring the authenticity of colors.

[0061] In an exemplary embodiment, the object side surface or the image side surface of at least one lens in the fixed focus lens may be an aspherical surface. An aspherical lens has a better curvature radius characteristic and has the advantages of improving distortion aberration and improving astigmatism aberration. By using an aspherical lens, aberrations occurring during imaging can be eliminated as much as possible, thereby improving imaging quality.

[0062] In an exemplary embodiment, the total optical length TTL of the fixed-focus lens may be less than or equal to 27 mm, which may achieve miniaturization.

[0063] In an exemplary embodiment, the diagonal size of the imaging surface IMG (imaging chip) of the fixed-focus lens can reach 9 mm, which can achieve a large target surface.

[0064] In an exemplary embodiment, the maximum field of view angle FVO of the fixed focus lens is greater than 55°. For example, the FVO is greater than 55.5° and less than 60°.

[0065] In an exemplary embodiment, the aperture number Fno of the fixed focus lens may be 2.80.

[0066] Those skilled in the art should understand that, without departing from the technical solution claimed in the present application, the number of lenses and spacers constituting the camera lens can be changed to obtain the various results and advantages described in this specification.

[0067] Specific embodiments of the imaging lens applicable to the above-mentioned embodiments will be further described below with reference to the accompanying drawings.

[0068] Example 1

[0069] The following reference Figure 1 A fixed-focus lens according to Embodiment 1 of the present application is described.

[0070] like Figure 1 As shown, the fixed focus lens includes a first lens L1, a second lens L2, a third lens L3, an aperture STO, a fourth lens L4, a fifth lens L5, a sixth lens L6, a seventh lens L7, an eighth lens L8 and a protective glass CG in sequence from the object side to the image side along the optical axis. Light incident from the object side passes through each lens and the protective glass CG in sequence and is finally imaged on the imaging surface IMG.

[0071] The first lens L1 has negative focal power, and its object side surface is convex, and its image side surface is concave. The second lens L2 has negative focal power, and its object side surface is concave, and its image side surface is convex. The third lens L3 has positive focal power, and its object side surface is convex, and its image side surface is concave. The fourth lens L4 has positive focal power, and its object side surface is convex, and its image side surface is convex. The fifth lens L5 has negative focal power, and its object side surface is concave, and its image side surface is convex. The sixth lens L6 has positive focal power, and its object side surface is convex, and its image side surface is convex. The seventh lens L7 has negative focal power, and its object side surface is concave, and its image side surface is concave. The eighth lens L8 has positive focal power, and its object side surface is convex, and its image side surface is convex. The light from the object passes through the surfaces of each lens in sequence and is finally imaged on the imaging surface IMG.

[0072] The fourth lens L4 and the fifth lens L5 form a cemented lens. The sixth lens L6 and the seventh lens L7 form a cemented lens.

[0073] The third lens L3 and the eighth lens L8 are plastic aspherical lenses.

[0074] The total effective focal length F of the fixed-focus lens is 8.98mm, the aperture number Fno is 2.80, and the maximum field of view FVO is 55.65°.

[0075] Table 1 shows the basic parameters of the fixed-focus lens of Example 1, wherein the units of the radius of curvature and thickness / distance are all in millimeters (mm). The numbers along the optical axis from the object side of the first lens to the image side of the protective glass CG are 1 to 17, and the cemented surface of the cemented lens is recorded as one surface.

[0076]

[0077] Table 2

[0078] In this embodiment, the object side surface and the image side surface of the third lens L3 and the eighth lens L8 of the fixed focus lens are both aspherical surfaces, and the surface shape x of each aspherical lens can be defined by but not limited to the following aspherical surface formula:

[0079]

[0080] Wherein, x is the distance vector height from the vertex of the aspheric surface when the aspheric surface is at a height of h along the optical axis; c is the paraxial curvature of the aspheric surface, c=1 / R (i.e., the paraxial curvature c is the reciprocal of the curvature radius R in Table 2 above); k is the cone coefficient; Ai is the correction coefficient of the i-th order of the aspheric surface. Table 2 shows the cone coefficient k and the high-order coefficient A that can be used for each aspheric surface 5, 6, 14 and 15 in Example 1 4 , A 6 , A 8 , A 10 , A 12, A 14 and A 16 .

[0081] Face number k A4 A6 A8 A10 A12 A14 A16 5 0.00 -4.96E-05 3.29E-06 2.67E-08 0.00E+00 0.00E+00 0.00E+00 0.00E+00 6 0.00 2.13E-04 5.08E-06 -1.38E-07 0.00E+00 0.00E+00 0.00E+00 0.00E+00 14 -32.94 -3.22E-03 -4.11E-05 -1.36E-05 1.05E-06 -7.13E-08 0.00E+00 0.00E+00 15 42.06 -3.00E-03 -2.29E-05 -3.35E-06 2.56E-07 -1.09E-08 0.00E+00 0.00E+00

[0082] Table 2

[0083] For other parameters of Example 1, please refer to Table 9.

[0084] Figure 2 The optical distortion curve of the fixed-focus lens of Example 1 is shown, and the maximum absolute value of the optical distortion is |-5.04%|. Figure 2 It can be seen that the fixed-focus lens provided in Example 1 can achieve low distortion and has good aberration correction capability, thereby achieving good imaging quality.

[0085] Example 2

[0086] The following reference Figure 3 A fixed-focus lens according to Embodiment 2 of the present application is described. Figure 3 The fixed focal length lens shown is Figure 1 The fixed focal length lenses shown have the following differences.

[0087] The third lens L3 has positive power, and its object side surface is convex, and its image side surface is convex. The fifth lens L5 has negative power, and its object side surface is concave, and its image side surface is concave. The sixth lens L6 has positive power, and its object side surface is convex, and its image side surface is concave. The seventh lens L7 has positive power, and its object side surface is convex, and its image side surface is concave. The eighth lens L8 has positive power, and its object side surface is convex, and its image side surface is concave.

[0088] The fourth lens L4 and the fifth lens L5 constitute a cemented lens.

[0089] The second lens L2 and the eighth lens L8 are plastic aspherical lenses.

[0090] The total effective focal length F of the fixed-focus lens is 8.91mm and the maximum field of view FVO is 55.89°.

[0091] Table 3 shows the basic parameters of the fixed-focus lens of Example 2, where the units of the radius of curvature and thickness / distance are all in millimeters (mm). The numbers along the optical axis from the object side of the first lens to the image side of the protective glass CG are 1 to 18, and the cemented surface of the cemented lens is recorded as one surface.

[0092]

[0093] Table 3

[0094] In this embodiment, the object side surface and the image side surface of the second lens L2 and the eighth lens L8 of the fixed focus lens are both aspherical surfaces. Table 4 shows the cone coefficient k and the high-order coefficient A of each aspherical surface 3, 4, 15 and 16 that can be used in Example 2. 4 , A 6 , A 8 , A 10 , A 12 , A 14 and A 16 .

[0095]

[0096]

[0097] Table 4

[0098] For other parameters of Example 2, please refer to Table 9.

[0099] Figure 4 The optical distortion curve of the fixed-focus lens of Example 2 is shown, and the maximum absolute value of the optical distortion is |-4.91%|. Figure 4 It can be seen that the fixed-focus lens provided in Example 2 can achieve low distortion and has good aberration correction capability, thereby achieving good imaging quality.

[0100] Example 3

[0101] The following reference Figure 5 A fixed-focus lens according to Embodiment 3 of the present application is described. Figure 5 The fixed focal length lens shown is Figure 1 The fixed focal length lenses shown have the following differences.

[0102] The third lens L3 has positive power, and its object side surface is convex, and its image side surface is convex. The fifth lens L5 has negative power, and its object side surface is concave, and its image side surface is concave. The sixth lens L6 has positive power, and its object side surface is convex, and its image side surface is concave. The seventh lens L7 has positive power, and its object side surface is concave, and its image side surface is convex. The eighth lens L8 has negative power, and its object side surface is convex, and its image side surface is concave.

[0103] The fourth lens L4 and the fifth lens L5 constitute a cemented lens.

[0104] The seventh lens L7 and the eighth lens L8 are plastic aspherical lenses.

[0105] The total effective focal length F of the fixed-focus lens is 8.92mm, and the maximum field of view FVO is 55.97°.

[0106] Table 5 shows the basic parameters of the fixed-focus lens of Example 3, where the units of the radius of curvature and thickness / distance are all in millimeters (mm). The numbers along the optical axis from the object side of the first lens to the image side of the protective glass CG are 1 to 18, and the cemented surface of the cemented lens is recorded as one surface.

[0107]

[0108] Table 5

[0109] In this embodiment, the object side surface and the image side surface of the seventh lens L7 and the eighth lens L8 of the fixed focus lens are both aspherical surfaces. Table 6 shows the cone coefficient k and the high-order coefficient A of each aspherical surface 13, 14, 15 and 16 that can be used in Example 3. 4 , A 6 , A 8 , A 10 , A 12 , A 14 and A 16 .

[0110] Face number k A4 A6 A8 A10 A12 A14 A16 13 31.91 -1.49E-03 -1.91E-04 -2.85E-06 0.00E+00 0.00E+00 0.00E+00 0.00E+00 14 -1.54 -1.48E-03 -1.12E-04 2.14E-06 0.00E+00 0.00E+00 0.00E+00 0.00E+00 15 -0.75 -4.73E-03 -4.02E-05 2.57E-06 0.00E+00 0.00E+00 0.00E+00 0.00E+00 16 -0.98 -5.53E-03 1.13E-05 9.07E-07 0.00E+00 0.00E+00 0.00E+00 0.00E+00

[0111] Table 6

[0112] For other parameters of Example 3, please refer to Table 9.

[0113] Figure 6 The optical distortion curve of the fixed-focus lens of Example 3 is shown, and the maximum absolute value of the optical distortion is |-5.04%|. Figure 6 It can be seen that the fixed-focus lens provided in Example 3 can achieve low distortion and has good aberration correction capability, thereby achieving good imaging quality.

[0114] Example 4

[0115] The following reference Figure 7 A fixed-focus lens according to Embodiment 4 of the present application is described. Figure 7 The fixed focal length lens shown is Figure 1 The fixed focal length lenses shown have the following differences.

[0116] The third lens L3 has positive power, and its object side surface is convex, and its image side surface is convex. The fifth lens L5 has negative power, and its object side surface is concave, and its image side surface is concave. The sixth lens L6 has positive power, and its object side surface is convex, and its image side surface is concave. The seventh lens L7 has positive power, and its object side surface is convex, and its image side surface is convex. The eighth lens L8 has negative power, and its object side surface is convex, and its image side surface is concave.

[0117] The fourth lens L4 and the fifth lens L5 constitute a cemented lens.

[0118] The seventh lens L7 and the eighth lens L8 are plastic aspherical lenses.

[0119] The total effective focal length F of the fixed-focus lens is 8.92mm, and the maximum field of view FVO is 55.93°.

[0120] Table 7 shows the basic parameters of the fixed-focus lens of Example 4, where the units of the radius of curvature and thickness / distance are all in millimeters (mm). The numbers along the optical axis from the object side of the first lens to the image side of the protective glass CG are 1 to 18, and the cemented surface of the cemented lens is recorded as one surface.

[0121]

[0122]

[0123] Table 7

[0124] In this embodiment, the object side surface and the image side surface of the seventh lens L7 and the eighth lens L8 of the fixed focus lens are both aspherical surfaces. Table 8 shows the cone coefficient k and the high-order coefficient A of each aspherical surface 13, 14, 15 and 16 that can be used in Example 4. 4 , A 6 , A 8 , A 10 , A 12 , A 14 and A 16 .

[0125] Face number k A4 A6 A8 A10 A12 A14 A16 13 39.51 3.22E-03 -1.50E-04 -1.45E-06 0.00E+00 0.00E+00 0.00E+00 0.00E+00 14 -5.94 5.80E-03 -1.66E-04 -1.19E-06 0.00E+00 0.00E+00 0.00E+00 0.00E+00 15 -0.19 0.00E+00 -4.05E-03 -6.60E-05 7.69E-06 -2.82E-07 0.00E+00 0.00E+00 16 -1.13 0.00E+00 -7.31E-03 2.50E-04 -7.82E-06 1.07E-07 0.00E+00 0.00E+00

[0126] Table 8

[0127] For other parameters of Example 4, please refer to Table 9.

[0128] Figure 8 The optical distortion curve of the fixed-focus lens of Example 4 is shown, and the maximum absolute value of the optical distortion is |-5.05%|. Figure 8 It can be seen that the fixed-focus lens provided in Example 4 can achieve low distortion and has good aberration correction capability, thereby achieving good imaging quality.

[0129] Table 9 shows the values ​​of the conditional expressions of each example in Examples 1 to 4.

[0130] Conditional / Example 1 2 3 4 -0.6≤(R22+R31) / (R22-R31)≤0.3 0.01 -0.10 0.20 0.06 -2.4≤(R21+R22) / F≤-0.75 -1.54 -1.56 -2.17 -1.93 0.8≤F3 / F≤1.78 1.64 0.94 1.01 1.10 -1.83≤F4 / R42≤-0.95 -1.56 -1.08 -1.08 -1.46 0.6≤|R82 / R81|≤2.3 1.33 2.06 0.83 0.83 0.9≤Fa / F≤8.2 8.05 1.40 1.05 1.52 0.9≤|(Vd4-Vd5) / F45|≤4.5 1.04 3.37 4.15 1.45 -4.5≤F45 / F≤2 1.60 -1.53 -1.46 -3.98 1≤|F67 / F|≤3.9 2.47 1.20 1.37 1.70 12.38≤TTL*H / F≤13.70 13.47 12.56 13.06 13.05 2.76≤TTL / F≤3.1 3.01 2.80 2.92 2.91 5.5≤TTL / H≤6.12 6.03 5.58 5.80 5.80 0.26≤D1 / TTL≤0.35 0.29 0.31 0.34 0.30

[0131] Table 9

[0132] The present application also provides an imaging device, whose electronic photosensitive element can be a photosensitive coupled device (CCD) or a complementary metal oxide semiconductor element (CMOS). The imaging device can be an independent imaging device such as a digital camera, or an imaging module integrated in a mobile electronic device such as a mobile phone. The imaging device is equipped with the camera lens described above.

[0133] The above description is only a preferred embodiment of the present application and an explanation of the technical principles used. Those skilled in the art should understand that the scope of the invention involved in the present application is not limited to the technical solution formed by a specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the inventive concept. For example, the above features are replaced with the technical features with similar functions disclosed in this application (but not limited to) by each other.

Claims

1. A fixed-focus lens, characterized in that: The fixed focus lens includes, in order from the object side to the image side along the optical axis: The first lens has a negative optical power, and its object side surface is convex and its image side surface is concave; The second lens has a negative optical power, and its object side surface is concave and its image side surface is convex; The third lens has positive power and its object side surface is convex; a fourth lens element having positive refractive power, whose object-side surface is convex and whose image-side surface is convex; a fifth lens having negative optical power, whose object side surface is concave; a sixth lens having positive refractive power and a convex object-side surface; a seventh lens; and The eighth lens has a convex object side surface; At least one of the seventh lens and the eighth lens has positive refractive power; The fourth lens and the fifth lens form a cemented lens; The total optical length TTL of the fixed-focus lens, half the diagonal length H of the imaging surface of the fixed-focus lens, and the total effective focal length F of the fixed-focus lens satisfy the following conditions: 12.38≤TTL*H / F≤13.70; The effective focal length F3 of the third lens and the total effective focal length F of the fixed-focus lens satisfy the following: 0.8≤F3 / F≤1.

78.

2. The fixed-focus lens according to claim 1, characterized in that: The total optical length TTL of the fixed-focus lens and half the diagonal length H of the imaging surface of the fixed-focus lens satisfy the following conditions: 5.5≤TTL / H≤6.

12.

3. The fixed-focus lens according to claim 1, characterized in that: The total optical length TTL of the fixed-focus lens and the total effective focal length F of the fixed-focus lens satisfy: 2.76≤TTL / F≤3.

1.

4. The fixed-focus lens according to claim 1, characterized in that: The larger optical full aperture value D1 of the object side surface and the image side surface of the first lens and the total optical length TTL of the fixed-focus lens satisfy: 0.26≤D1 / TTL≤0.

35.

5. The fixed-focus lens according to claim 1, wherein: A curvature radius R22 of the image-side surface of the second lens and a curvature radius R31 of the object-side surface of the third lens satisfy: -0.6≤(R22+R31) / (R22-R31)≤0.

3.

6. The fixed-focus lens according to claim 1, wherein: A curvature radius R21 of the object-side surface of the second lens, a curvature radius R22 of the image-side surface of the second lens, and a total effective focal length F of the fixed-focus lens satisfy: -2.4≤(R21+R22) / F≤-0.

75.

7. The fixed-focus lens according to claim 1, wherein: An effective focal length F4 of the fourth lens and a curvature radius R42 of the image-side surface of the fourth lens satisfy: -1.83≤F4 / R42≤-0.

95.

8. The fixed-focus lens according to claim 1, wherein: A curvature radius R81 of the image-side surface of the eighth lens and a curvature radius R82 of the object-side surface of the eighth lens satisfy: 0.6≤|R82 / R81|≤2.

3.

9. The fixed-focus lens according to claim 1, wherein: The sixth lens and the seventh lens are a cemented lens.

10. The fixed-focus lens according to any one of claims 1 to 9, characterized in that: It also includes an aperture, and the effective combined focal length Fa of the front lens group located on the object side of the aperture and the total effective focal length F of the fixed-focus lens satisfy: 0.9≤Fa / F≤8.

2.

11. The fixed-focus lens according to any one of claims 1 to 9, characterized in that: The Abbe number of the material used for the fourth lens, the Abbe number of the material used for the fifth lens, and the combined effective focal length F45 of the fourth lens and the fifth lens satisfy: 0.9≤|(Vd4-Vd5) / F45|≤4.

5.

12. The fixed-focus lens according to any one of claims 1 to 9, characterized in that: The combined effective focal length F45 of the fourth lens and the fifth lens and the total effective focal length F of the fixed-focus lens satisfy: -4.5≤F45 / F≤2.

13. The fixed-focus lens according to any one of claims 1 to 9, characterized in that: A combined effective focal length F67 of the sixth lens and the seventh lens and a total effective focal length F of the fixed-focus lens satisfy: 1≤|F67 / F|≤3.

9.

14. The fixed-focus lens according to any one of claims 1 to 9, characterized in that: The first to eighth lenses include glass lenses and plastic lenses.

Images