prime lens

Abstract

This application discloses a fixed-focus lens, which includes, along the optical axis from the object side to the image side, the following lenses in sequence: 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, a seventh lens, and an eighth lens with positive optical power; the object side of the first lens is convex, and the image side is concave; the object side of the second lens is concave, and the image side is convex; the object side of the third lens is convex; the object side of the fourth lens is convex, and the image side is convex; the object side of the fifth lens is concave; the object side of the sixth lens is convex; the object side of the eighth lens is convex; at least one of the seventh and eighth lenses has positive optical power; 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: 12.38≤TTL*H / F≤13.70.

Description

Technical Field

[0001] This application relates to the field of optical devices, specifically to a fixed-focus lens. Background Technology

[0002] With the rapid development of modern photography and videography technologies, fixed-focus lenses are widely used in video conferencing, security monitoring, and action photography. Customer demands for lenses are increasingly focused on large focal lengths, low distortion, and high resolution. To achieve these characteristics in video conferencing lenses, it's generally necessary to increase the number of lens elements to balance system performance. This can result in lenses that are excessively long and bulky. Summary of the Invention

[0003] This application provides a fixed-focus lens comprising, along the optical axis from the object side to the image side, the following elements in sequence: 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 and eighth lens with positive optical power; the object side of the first lens is convex, and the image side is concave; the object side of the second lens is concave, and the image side is convex; the third lens... The object-side surface of the fourth lens is convex; the object-side surface of the fifth 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 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: 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 this application, 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: 5.5≤TTL / H≤6.12.

[0005] According to an exemplary embodiment of this 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 this application, the larger optical aperture value D1 of the object side and image side 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 this application, the radius of curvature R22 of the image side of the second lens and the radius of curvature R31 of the object side of the third lens satisfy: -0.6≤(R22+R31) / (R22-R31)≤0.3.

[0008] According to an exemplary embodiment of this application, the radius of curvature R21 of the object side of the second lens, the radius of curvature R22 of the image side of the second lens, and the 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 this application, the effective focal length F4 of the fourth lens and the radius of curvature R42 of the image side surface of the fourth lens satisfy: -1.83≤F4 / R42≤-0.95.

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

[0011] According to an exemplary embodiment of this application, the fixed-focus lens further includes an aperture stop, wherein the effective combined focal length Fa of the front lens group of the aperture 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 this application, the fourth lens and the fifth lens form a cemented lens, wherein 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 and fifth lenses satisfy: 0.9≤|(Vd4-Vd5) / F45|≤4.5.

[0013] According to an exemplary embodiment of this 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 this application, the combined effective focal length F67 of the sixth lens and the seventh lens and the total effective focal length F of the fixed-focus lens satisfy: 1≤|F67 / F|≤3.9.

[0015] According to an exemplary embodiment of this 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 this application, the sixth lens and the seventh lens are cemented lenses.

[0017] The fixed-focus lens provided in this application has 8 lenses. 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 the following condition: 12.38≤TTL*H / F≤13.70. When this relationship is satisfied, it can meet the market demand for miniaturization of fixed-focus lenses while adapting to large-sized imaging surface IMGs (imaging chips), thus enabling the fixed-focus lens to simultaneously meet the market demand for both large target surfaces and miniaturization. The effective focal length F3 of the third lens and the total effective focal length F of the fixed-focus lens satisfy the following condition: 0.8≤F3 / F≤1.78. By reasonably setting the effective focal length of the third lens, it is possible to effectively collect and compress the incident light from the front, so that the light can smoothly transition to the rear optical system, reduce the generation of aberrations, and thus improve the image quality of the lens. Attached Figure Description

[0018] Other features, objects, and advantages of this application will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings. Wherein:

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

[0020] Figure 2 The distortion curve of a fixed-focus lens according to Embodiment 1 of this application is shown;

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

[0022] Figure 4 The distortion curve of a fixed-focus lens according to Embodiment 2 of this application is shown;

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

[0024] Figure 6 The distortion curve of a fixed-focus lens according to Embodiment 3 of this application is shown;

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

[0026] Figure 8 The distortion curve of a fixed-focus lens according to Embodiment 4 of this application is shown. Detailed Implementation

[0027] To better understand this application, various aspects of this application will be described in more detail with reference to the accompanying drawings. It should be understood that these detailed descriptions are merely illustrative of exemplary embodiments of this application and are not intended to limit the scope of this application in any way. Throughout the specification, the same reference numerals refer to the same elements.

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

[0029] In the accompanying 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 illustrated by way of example. That is, the shapes of the spherical or aspherical surfaces are not limited to those shown in the drawings. The drawings are for illustrative purposes 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 location of the convexity 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 location of the concaveness 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 subject is called the object-side surface of the lens, and the surface of each lens closest to the image plane is called the image-side surface of the lens.

[0031] It should also be understood that the terms "comprising" 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. Furthermore, when describing embodiments of this application, the word "may" is used to mean "one or more embodiments of this application." And the term "exemplary" is intended to refer to an example or illustration.

[0032] Unless otherwise specified, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. It should also be understood that terms (e.g., those defined in common dictionaries) shall be interpreted as having the meaning consistent with their meaning in the context of the relevant art and shall not be interpreted in an idealized or overly formalized sense, unless expressly so specified herein.

[0033] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0034] refer to Figure 1 , Figure 3 , Figure 5 and Figure 7 One aspect of this application provides a fixed-focus lens that includes, in sequence along the optical axis from the object side to the image side, 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.

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

[0036] In an exemplary embodiment, the second lens L2 has negative optical power, a concave object side and a convex image side, with the convex surface facing the image side in a crescent shape, which can initially correct the astigmatism of the optical system, while effectively controlling the direction of light and achieving a larger aperture.

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

[0038] In an exemplary embodiment, the fourth lens L4 has positive optical power, with both the object side and the image side being convex. The biconvex structure helps to reduce the incident angle of light after passing through the aperture, allowing more light to enter the optical system on the image side and improving the illuminance of the optical system.

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

[0040] In an exemplary embodiment, the sixth lens L6 has positive optical power and the object side is convex, while the image side can be convex or concave, which enables smooth light transition, helps correct on-axis aberrations, and improves the imaging quality of the optical lens.

[0041] In an exemplary embodiment, the seventh lens L7 may have optical power, which can be positive or negative. By reasonably setting the optical power and shape of the seventh lens L7, the light path can be effectively controlled, and the light angle can be raised, so that the imaging height can match the large-sized chip and achieve 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 effectively reducing tolerance sensitivity, thereby improving the imaging quality of the optical system. In addition, they can reduce the assembly sensitivity of the fixed-focus lens, thereby reducing the processing difficulty 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 optical power, which can be positive or negative. The object-side surface of the eighth lens L8 is convex, and the surface shape of the eighth lens L8 is set aspherical. Through the aspherical curvature design, the distortion of the edge field of view can be effectively corrected, so that the optical distortion is ≤|-5%|, achieving low distortion of the optical system and improving image quality.

[0044] In an exemplary embodiment, at least one of the seventh lens L7 and the eighth lens L8 has positive optical power.

[0045] In an exemplary embodiment, the shape of the image-side surface of the third lens L3, the fifth lens L5, the sixth lens L6, and the eighth lens L8 is not limited.

[0046] In an exemplary embodiment, the fixed-focus lens may further include an aperture stop. The aperture stop may be located between the third lens L3 and the fourth lens L4. In this case, the light entering the optical system can be effectively gathered, the overall length of the optical system can be shortened, and the maximum aperture of the optical system can be reduced, which is beneficial for achieving miniaturization design.

[0047] In an exemplary embodiment, the total optical length (TTL) of the fixed-focus lens, half the diagonal length (H) of the imaging sensor (IMG) of the fixed-focus lens, and the total effective focal length (F) of the fixed-focus lens satisfy the following formula: 12.38 ≤ TTL * H / F ≤ 13.70. This formula reflects the constraints of the optical lens in terms of the target surface size and volume. When this formula is satisfied, it is possible to adapt the fixed-focus lens to a large-sized imaging sensor (IMG), meet the market demand for miniaturization of fixed-focus lenses, and enable the fixed-focus lens to simultaneously meet the market requirements of large target surface size and miniaturization. The units for the total optical length (TTL), half the diagonal length (H) of the imaging sensor (IMG), and the total effective focal length (F) of the fixed-focus lens are all 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. By reasonably setting the effective focal length of the third lens, the incident light in front can be effectively collected and compressed, so that the light can smoothly transition to the optical system behind, reducing the generation of aberrations and thus improving 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 plane (IMG) of the fixed-focus lens satisfy: 5.5 ≤ TTL / H ≤ 6.12. Given a certain image height of the optical system, by controlling the ratio of the image height to the focal length, the total length of the optical system is limited to a smaller value, thereby achieving miniaturization.

[0050] In an exemplary embodiment, the total optical length (TTL) and the total effective focal length (F) of the fixed-focus lens satisfy the condition: 2.76 ≤ TTL / F ≤ 3.1. Given a certain total effective focal length of the optical system, by controlling the ratio of the total optical length to the total effective focal length, the optical system is limited to have a smaller total optical length, thereby achieving miniaturization.

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

[0052] In an exemplary embodiment, the radius of curvature R22 of the image-side surface of the second lens L2 and the radius of curvature R31 of the object-side surface of the third lens L3 satisfy: -0.6 ≤ (R22 + R31) / (R22 - R31) ≤ 0.3. Reasonably configuring the values ​​of the radii of curvature 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 rays, which is beneficial for correcting astigmatism and field curvature, thereby improving resolution quality.

[0053] In an exemplary embodiment, the radius of curvature R21 of the object-side surface of the second lens L2, the radius of curvature 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. Properly configuring the radii of curvature of the object-side and image-side surfaces of the second lens L2 is beneficial for correcting astigmatism and improving the resolving power of the optical system.

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

[0055] In an exemplary embodiment, the radius of curvature R81 of the image-side surface of the eighth lens L8 and the radius of curvature R82 of the object-side surface of the eighth lens L8 satisfy: 0.6 ≤ |R82 / R81| ≤ 2.3. Reasonably controlling the ratio of the radii of curvature of the object-side and image-side surfaces of the eighth lens L8, and appropriately setting the shape of the eighth lens L8, is beneficial for better distortion correction, ensuring that optical distortion is ≤ |-5%|, thus achieving low distortion in the optical system.

[0056] In an exemplary embodiment, when the fixed-focus lens further includes an aperture stop, the effective combined focal length Fa of the front lens group of the aperture stop and the total effective focal length F of the fixed-focus lens satisfy: 0.9 ≤ Fa / F ≤ 8.2. Reasonably allocating the effective combined focal length of the front lens group of the aperture stop is beneficial for better distortion correction, ensuring optical distortion ≤ |-5%|, thus achieving low distortion in 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 fifth lens L5 and the fourth lens L4 are combined to form a cemented lens. 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 the following condition: 0.9 ≤ |(Vd4-Vd5) / F45| ≤ 4.5. By reasonably setting the ratio of the Abbe number difference between the fourth lens L4 and the fifth lens L5 to the combined effective focal length of the fourth lens L4 and the fifth lens L5, when the above relationship is satisfied, the chromatic aberration of the optical system can be effectively corrected, the authenticity of colors can be restored, and the image 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, as well as the total effective focal length F of the fixed-focus lens, satisfy: -4.5 ≤ F45 / F ≤ 2. Properly configuring the combined effective focal length of the fourth lens L4 and the fifth lens L5 helps control the direction of light, allowing it to smoothly transition to the rear of the optical system after passing through the aperture stop. This helps balance various aberrations, improves lens resolution, and also helps reduce tolerance sensitivity, thereby increasing the lens's production yield.

[0059] In an exemplary embodiment, the combined effective focal length F67 of the sixth lens L6 and the seventh lens L7, as well as the total effective focal length F of the fixed-focus lens, satisfy: 1 ​​≤ |F67 / F| ≤ 3.9. Properly configuring 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 helps balance various aberrations, improves lens resolution, and also helps reduce tolerance sensitivity, thereby increasing the lens's production yield.

[0060] In an exemplary embodiment, the first lens L1 to the eighth lens L8 include glass lenses and plastic lenses. The use of glass-plastic hybrid material lenses in the fixed-focus lens helps reduce the cost of the optical system and balances the high and low temperature performance of the fixed-focus lens, achieving high image quality within the range of -20℃ to 60℃. Using glass lenses in one or more lenses helps correct chromatic aberration in the optical system and better reproduces the true colors.

[0061] In an exemplary embodiment, the object-side or image-side surface of at least one lens in a fixed-focus lens can be aspherical. Aspherical lenses have better radius of curvature characteristics, which has the advantage of improving distortion aberrations and astigmatism aberrations. By using aspherical lenses, aberrations that occur during imaging can be eliminated as much as possible, thereby improving image quality.

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

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

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

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

[0066] Those skilled in the art will understand that, without departing from the technical solutions claimed in this 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] The following describes in further detail, with reference to the accompanying drawings, specific embodiments of the camera lens applicable to the above-described embodiments.

[0068] Example 1

[0069] The following is for reference Figure 1 Describes a fixed-focus lens according to Embodiment 1 of this application.

[0070] like Figure 1 As shown, the fixed-focus lens, along the optical axis from the object side to the image side, includes, in sequence, a first lens L1, a second lens L2, a third lens L3, an aperture stop 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. Light incident from the object side passes through each lens and the protective glass CG in sequence and is finally imaged onto the imaging plane IMG.

[0071] Lens L1 has negative optical power, with a convex object-side surface and a concave image-side surface. Lens L2 has negative optical power, with a concave object-side surface and a convex image-side surface. Lens L3 has positive optical power, with a convex object-side surface and a concave image-side surface. Lens L4 has positive optical power, with a convex object-side surface and a convex image-side surface. Lens L5 has negative optical power, with a concave object-side surface and a convex image-side surface. Lens L6 has positive optical power, with a convex object-side surface and a convex image-side surface. Lens L7 has negative optical power, with a concave object-side surface and a concave image-side surface. Lens L8 has positive optical power, with a convex object-side surface and a convex image-side surface. Light from the object passes sequentially through the surfaces of each lens and is ultimately imaged on the imaging plane 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 fixed-focus lens has a total effective focal length of 8.98mm, an aperture of 2.80, and a maximum field of view of 55.65°.

[0075] Table 1 shows the basic parameters of the fixed-focus lens of Embodiment 1, where the units for radius of curvature and thickness / distance are millimeters (mm). The lenses are numbered sequentially from the object-side surface of the first lens to the image-side surface of the protective glass CG along the optical axis from 1 to 17, and the cementing surface of the cemented lens is referred to as one surface.

[0076]

[0077] Table 2

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

[0079]

[0080] Where x is the distance vector from the vertex of the aspherical surface at a height of h along the optical axis; c is the paraxial curvature of the aspherical surface, c = 1 / R (i.e., the paraxial curvature c is the reciprocal of the radius of curvature R in Table 2 above); k is the conic coefficient; Ai is the i-th order correction coefficient of the aspherical surface. Table 2 gives the conic coefficient k and higher-order coefficients A4, A6, A8, A15 that can be used for the aspherical surfaces 5, 6, 14, and 15 in Example 1. 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] Other parameters for Example 1 are shown in Table 9.

[0084] Figure 2 The optical distortion curve of the fixed-focus lens of Example 1 is shown, with a maximum absolute value of optical distortion of |-5.04%|. According to... Figure 2 As can be seen, the fixed-focus lens given in Example 1 can achieve low distortion and has good aberration correction capability, thus achieving good image quality.

[0085] Example 2

[0086] The following is for reference Figure 3 Describes a fixed-focus lens according to Embodiment 2 of this application. Figure 3 The fixed-focus lens shown is Figure 1 The fixed-focus lenses shown have the following differences.

[0087] The third lens L3 has positive optical power, with both its object-side and image-side surfaces being convex. The fifth lens L5 has negative optical power, with both its object-side and image-side surfaces being concave. The sixth lens L6 has positive optical power, with both its object-side and image-side surfaces being convex. The seventh lens L7 has positive optical power, with both its object-side and image-side surfaces being convex. The eighth lens L8 has positive optical power, with both its object-side and image-side surfaces being convex.

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

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

[0090] The total effective focal length 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 in Embodiment 2, where the units for radius of curvature and thickness / distance are millimeters (mm). The lenses are numbered sequentially from the object-side surface of the first lens to the image-side surface of the protective glass CG along the optical axis, from 1 to 18. The cemented surface of the cemented lens is referred to as one surface.

[0092]

[0093] Table 3

[0094] In this embodiment, the object-side surface and image-side surface of the second lens L2 and the eighth lens L8 of the fixed-focus lens are both aspherical. Table 4 shows the conic coefficient k and higher-order coefficients A4, A6, A8, and A6 that can be used for the aspherical surfaces 3, 4, 15, and 16 in Embodiment 2. 10 A 12 A 14 and A 16 .

[0095] Face number k A4 A6 A8 A10 A12 A14 A16 3 0.00 1.13E-03 -5.01E-06 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 4 0.00 4.55E-04 -1.59E-05 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 15 0.67 -4.59E-03 -7.35E-05 -9.89E-06 0.00E+00 0.00E+00 0.00E+00 0.00E+00 16 5.64 -3.50E-03 -5.41E-05 1.23E-06 0.00E+00 0.00E+00 0.00E+00 0.00E+00

[0096] Table 4

[0097] Other parameters for Example 2 are shown in Table 9.

[0098] Figure 4 The optical distortion curve of the fixed-focus lens of Example 2 is shown, with a maximum absolute value of optical distortion of |-4.91%|. According to... Figure 4 As can be seen, the fixed-focus lens given in Example 2 can achieve low distortion and has good aberration correction capability, thus achieving good image quality.

[0099] Example 3

[0100] The following is for reference Figure 5 Describes a fixed-focus lens according to Embodiment 3 of this application. Figure 5 The fixed-focus lens shown is Figure 1 The fixed-focus lenses shown have the following differences.

[0101] The third lens L3 has positive optical power, with both its object-side and image-side surfaces being convex. The fifth lens L5 has negative optical power, with both its object-side and image-side surfaces being concave. The sixth lens L6 has positive optical power, with both its object-side and image-side surfaces being convex. The seventh lens L7 has positive optical power, with both its object-side and image-side surfaces being concave. The eighth lens L8 has negative optical power, with both its object-side and image-side surfaces being convex.

[0102] The fourth lens L4 and the fifth lens L5 form a cemented lens.

[0103] The seventh lens L7 and the eighth lens L8 are plastic aspherical lenses.

[0104] The total effective focal length of the fixed-focus lens is 8.92mm, and the maximum field of view (FVO) is 55.97°.

[0105] Table 5 shows the basic parameters of the fixed-focus lens in Embodiment 3, where the units for radius of curvature and thickness / distance are millimeters (mm). The lenses are numbered sequentially from the object-side surface of the first lens to the image-side surface of the protective glass CG along the optical axis, from 1 to 18. The cemented surface of the cemented lens is referred to as one surface.

[0106]

[0107] Table 5

[0108] In this embodiment, the object-side surface and image-side surface of the seventh lens L7 and the eighth lens L8 of the fixed-focus lens are both aspherical. Table 6 gives the conic coefficient k and higher-order coefficients A4, A6, A8, and A6 of the aspherical surfaces 13, 14, 15, and 16 that can be used in Embodiment 3. 10 A 12 A 14 and A 16 .

[0109] 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

[0110] Table 6

[0111] Other parameters for Example 3 are shown in Table 9.

[0112] Figure 6 The optical distortion curve of the fixed-focus lens in Example 3 is shown, with a maximum absolute value of optical distortion of |-5.04%|. According to... Figure 6 As can be seen, the fixed-focus lens given in Example 3 can achieve low distortion and has good aberration correction capability, thus achieving good image quality.

[0113] Example 4

[0114] The following is for reference Figure 7 Describes a fixed-focus lens according to Embodiment 4 of this application. Figure 7 The fixed-focus lens shown is Figure 1 The fixed-focus lenses shown have the following differences.

[0115] The third lens L3 has positive optical power, and its object side and image side are both convex.

[0116] The second lens L2 and the eighth lens L8 are plastic aspherical lenses.

[0117] The total effective focal length of the fixed-focus lens is 8.93mm, and the maximum field of view (FVO) is 55.83°.

[0118] Table 7 shows the basic parameters of the fixed-focus lens of Embodiment 4, where the units for radius of curvature and thickness / distance are millimeters (mm). The lenses are numbered sequentially from the object-side surface of the first lens to the image-side surface of the protective glass CG along the optical axis from 1 to 17, and the cementing surface of the cemented lens is referred to as one surface.

[0119]

[0120] Table 7

[0121] In this embodiment, the object-side surface and image-side surface of the second lens L2 and the eighth lens L8 of the fixed-focus lens are both aspherical. Table 8 gives the conic coefficient k and higher-order coefficients A4, A6, A8, and A6 that can be used for the aspherical surfaces 3, 4, 14, and 15 in Embodiment 4. 10 A 12 A 14 and A 16 .

[0122] Face number k A4 A6 A8 A10 A12 A14 A16 3 -0.79 2.22E-03 2.02E-05 -1.14E-06 0.00E+00 0.00E+00 0.00E+00 0.00E+00 4 -0.50 2.30E-03 1.87E-05 -3.79E-07 0.00E+00 0.00E+00 0.00E+00 0.00E+00 14 90.00 -3.06E-03 -1.11E-04 1.57E-06 -3.12E-07 -4.65E-09 0.00E+00 0.00E+00 15 -79.92 -2.45E-03 -8.53E-05 4.47E-06 -2.08E-07 2.75E-09 0.00E+00 0.00E+00

[0123] Table 8

[0124] Other parameters for Example 4 are shown in Table 9.

[0125] Figure 8 The optical distortion curve of the fixed-focus lens in Example 4 is shown, with a maximum absolute value of optical distortion of |-4.92%|. According to... Figure 8 As can be seen, the fixed-focus lens given in Example 4 can achieve low distortion and has good aberration correction capability, thus achieving good image quality.

[0126] Table 9 shows the values ​​of the conditional expressions for each of the embodiments in Examples 1-4.

[0127] Conditional / Example 1 2 3 4 -0.6≤(R22+R31) / (R22-R31)≤0.3 0.01 -0.10 0.20 -0.48 -2.4≤(R²₁+R²₂) / F≤-0.75 -1.54 -1.56 -2.17 -0.98 0.8 ≤ F3 / F ≤ 1.78 1.64 0.94 1.01 1.06 -1.83≤F4 / R42≤-0.95 -1.56 -1.08 -1.08 -1.71 0.6 ≤ |R82 / R81| ≤ 2.3 1.33 2.06 0.83 2.01 0.9 ≤ Fa / F ≤ 8.2 8.05 1.40 1.05 7.66 0.9 ≤ |(Vd4-Vd5) / F45| ≤ 4.5 1.04 3.37 4.15 2.89 -4.5≤F45 / F≤2 1.60 -1.53 -1.46 1.55 1≤|F67 / F|≤3.9 2.47 1.20 1.37 3.48 12.38≤TTL*H / F≤13.70 13.47 12.56 13.06 12.79 2.76≤TTL / F≤3.1 3.01 2.80 2.92 2.86 5.5≤TTL / H≤6.12 6.03 5.58 5.80 5.69 0.26≤D1 / TTL≤0.35 0.29 0.31 0.34 0.29

[0128] Table 9

[0129] This application also provides an imaging device, whose electronic photosensitive element can be a photocoupled device (CCD) or a complementary metal oxide semiconductor device (CMOS). The imaging device can be a stand-alone imaging device such as a digital camera, or an imaging module integrated into a mobile electronic device such as a mobile phone. The imaging device is equipped with the camera lens described above.

[0130] The above description is merely a preferred embodiment of this application and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the inventive concept. For example, technical solutions formed by substituting the above features with (but not limited to) technical features with similar functions disclosed in this application.

Claims

1. A fixed-focus lens, characterized in that, The fixed-focus lens, along the optical axis from the object side to the image side, comprises, in sequence: The first lens with negative optical power has a convex object side and a concave image side. A second lens with negative optical power has a concave object side and a convex image side. A third lens with positive optical power has a convex object-side surface; The fourth lens with positive optical power has a convex object-side surface and a convex image-side surface; The fifth lens has negative optical power and its object side is concave. The sixth lens has positive optical power and its object side is convex. A seventh lens with optical power; and The eighth lens, which has optical power, has a convex object side. At least one of the seventh lens and the eighth lens has positive optical power; The fixed-focus lens has eight lenses with optical power. 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: 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 condition: 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: 5.5≤TTL / H≤6.

12.

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

1.

4. The fixed-focus lens according to claim 1, characterized in that, The larger optical aperture value D1 of the object side and image side 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, characterized in that, The radius of curvature R22 of the image side of the second lens and the radius of curvature R31 of the object side of the third lens satisfy: -0.6≤(R22+R31) / (R22-R31)≤0.

3.

6. The fixed-focus lens according to claim 1, characterized in that, The radius of curvature R21 of the object side of the second lens, the radius of curvature R22 of the image side of the second lens, and the 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, characterized in that, The effective focal length F4 of the fourth lens and the radius of curvature 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, characterized in that, The radius of curvature R82 of the image side of the eighth lens and the radius of curvature R81 of the object side of the eighth lens satisfy: 0.6≤|R82 / R81|≤2.

3.

9. The fixed-focus lens according to claim 1, characterized in that, The sixth lens and the seventh lens are cemented lenses.

10. The fixed-focus lens according to any one of claims 1 to 9, characterized in that, It also includes an aperture stop, and the effective combined focal length Fa of the front lens group located on the object side of the aperture stop and the total effective focal length F of the fixed focal length 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 fourth lens and the fifth lens form a cemented lens. The Abbe number Vd4 of the material used for the fourth lens, the Abbe number Vd5 of the material used for the fifth lens, and the combined effective focal length F45 of the fourth and fifth lenses 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, The combined effective focal length F67 of the sixth lens and the seventh lens, and the 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 the eighth lenses include glass lenses and plastic lenses.

15. The fixed-focus lens according to any one of claims 1 to 9, characterized in that, The fixed-focus lens satisfies at least one of the following conditions: 12.56≤TTL*H / F≤13.47; 0.94≤F3 / F≤1.64; 5.58≤TTL / H≤6.03; 2.80≤TTL / F≤3 .01; 0.29≤D1 / TTL≤0.34; -0.48≤(R22+R31) / (R22-R31)≤0.20; -2.17≤(R21+R 22) / F≤-0.98; -1.71≤F4 / R42≤-1.08; 0.83≤|R82 / R81|≤2.06; 1.05≤Fa / F≤8. 05; 1.04≤|(Vd4-Vd5) / F45|≤4.15; -1.53≤F45 / F≤1.60; 1.20≤|F67 / F|≤3.48; Wherein, TTL is the total optical length of the fixed-focus lens, H is half the diagonal length of the imaging surface of the fixed-focus lens, F is the total effective focal length of the fixed-focus lens, F3 is the effective focal length of the third lens, D1 is the larger optical aperture value between the object-side and image-side surfaces of the first lens, R22 is the radius of curvature of the image-side surface of the second lens, R31 is the radius of curvature of the object-side surface of the third lens, R21 is the radius of curvature of the object-side surface of the second lens, F4 is the effective focal length of the fourth lens, R4 2 is the radius of curvature of the image side of the fourth lens, R81 is the radius of curvature of the object side of the eighth lens, R82 is the radius of curvature of the image side of the eighth lens, Fa is the effective combined focal length of the front lens group located on the object side of the aperture of the fixed-focus lens, Vd4 is the Abbe number of the material used in the fourth lens, Vd5 is the Abbe number of the material used in the fifth lens, F45 is the combined effective focal length of the fourth lens and the fifth lens, and F67 is the combined effective focal length of the sixth lens and the seventh lens.

Images