Prime lens

Abstract

The invention discloses a prime lens, and the prime lens sequentially comprises a first lens with positive focal power, a second lens with negative focal power, a third lens with positive focal power and a fourth lens with negative focal power from an object side to an image side along an optical axis, the second lens has focal power; the third lens has focal power; the object side surface of the fourth lens is a convex surface; the fifth lens has focal power; the object side surface and the image side surface of the sixth lens are both concave surfaces, and the positive and negative attributes of the focal power of the second lens and the third lens are opposite; the image side surface of the first lens and the image side surface of the fifth lens are convex surfaces or concave surfaces; the curvature radius R21 of the object side face of the second lens, the curvature radius R22 of the image side face of the second lens, the curvature radius R31 of the object side face of the third lens and the curvature radius R32 of the image side face of the third lens meet the condition that (R21 + R22) / (R31 + R32) is larger than or equal to 0.22 and smaller than or equal to 2.9.

Description

Technical Field

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

[0002] With the continuous upgrading and development of Internet technology, video lenses have been widely used in video conferencing, online teaching, online video shooting and other fields, and have received more and more attention from the public. Therefore, the requirements for their image quality are also getting higher and higher.

[0003] However, the video conferencing cameras currently used generally have the following shortcomings:

[0004] 1. The image size of the video conferencing lens is too small;

[0005] 2. Current video conferencing lenses often have poor lens distortion control when achieving a large field of view and large frame size, which causes obvious distortion in the captured images and affects the post-processing of images.

[0006] 3. The current video conferencing lens configuration makes it difficult to make good corrections for system aberrations, resulting in poor imaging quality;

[0007] 4. If the current video conferencing lens needs to improve its optical imaging quality, it needs to increase the number of lenses to improve it. At this time, there will be problems such as the total length of the lens being too long and the size being too large, which makes the overall cost and weight of the lens too high.

[0008] Therefore, in summary, designing a fixed-focus lens with low distortion, small size, large image plane size, high resolution and low cost has become a market development trend. Summary of the invention

[0009] According to an embodiment of the present application, a fixed-focus lens is provided, which includes, in order from the object side to the image side along the optical axis: a first lens with positive optical power, whose object side surface is convex; a second lens with optical power, when the optical power of the second lens is positive, its object side surface is concave, and its image side surface is convex; when the optical power of the second lens is negative, its object side surface is convex, and its image side surface is concave; a third lens with optical power, when the optical power of the third lens is positive, its image side surface is convex; when the optical power of the third lens is negative, its image side surface is concave; a fourth lens, whose object side surface is convex; a fifth lens with optical power, when the optical power of the fifth lens is positive , its object side surface is convex; when the optical power of the fifth lens is negative, its object side surface is concave; and the sixth lens with negative optical power, its object side surface and image side surface are both concave, wherein the positive and negative properties of the optical power of the second lens and the third lens are opposite; the image side surface of the first lens and the image side surface of the fifth lens are both convex or both are concave; and the curvature radius R21 of the object side surface of the second lens, the curvature radius R22 of the image side surface of the second lens, the curvature radius R31 of the object side surface of the third lens and the curvature radius R32 of the image side surface of the third lens satisfy: 0.22≤|(R21+R22) / (R31+R32)|≤2.9.

[0010] In one or more embodiments, the Abbe number Vd1 of the first lens and the effective focal length F1 of the first lens satisfy: 3.48≤Vd1 / F1≤7.73.

[0011] In one or more embodiments, the effective focal length F1 of the first lens and the curvature radius R11 of the object-side surface of the first lens satisfy: 1.80≤F1 / R11≤2.16.

[0012] In one or more embodiments, the combined effective focal length F23 of the second lens and the third lens and the total effective focal length F of the fixed focus lens satisfy: 1.5≤|F23 / F|≤7.5.

[0013] In one or more embodiments, the combined effective focal length of the second lens and the third lens, the center thickness value d2 of the second lens, and the center thickness value d3 of the third lens satisfy: 12≤|F23 / (d2+d3)|≤32.

[0014] In one or more embodiments, an effective focal length F4 of the fourth lens, a curvature radius R41 of the object-side surface of the fourth lens, and a curvature radius R42 of the image-side surface of the fourth lens satisfy: 0.2≤|F4 / (R41+R42)|≤4.3.

[0015] In one or more embodiments, the combined effective focal length F56 of the fifth lens and the sixth lens and the total effective focal length F of the fixed focus lens satisfy: -1.5≤F56 / F≤-0.23.

[0016] In one or more embodiments, a radius of curvature R12 of the image side surface of the first lens and a radius of curvature R52 of the image side surface of the fifth lens satisfy: 1≤|(R12+R52) / (R12-R52)|≤7.5.

[0017] In one or more embodiments, the total length TTL of the optical system of the fixed-focus lens and half the diagonal length H of the effective pixel area on the imaging plane of the fixed-focus lens satisfy the following: 1.98≤TTL / H≤2.4.

[0018] In one or more embodiments, the total optical system length TTL of the fixed-focus lens and the total effective focal length F of the fixed-focus lens satisfy: 1.21≤TTL / F≤1.47.

[0019] In one or more embodiments, a maximum value CTmax of a center thickness of each lens in the fixed-focus lens on the optical axis and a minimum value CTmin of a center thickness of each lens in the fixed-focus lens on the optical axis satisfy: 3.62≤CTmax / CTmin≤5.2.

[0020] In one or more embodiments, a center thickness value d4 of the fourth lens and a refractive index Nd4 of the fourth lens satisfy: 0.7≤d4 / Nd4≤2.1.

[0021] In one or more embodiments, a curvature radius R51 of the object-side surface of the fifth lens and a curvature radius R52 of the image-side surface of the fifth lens satisfy: -3.2≤(R51+R52) / (R51-R52)≤-0.75.

[0022] In one or more embodiments, the effective focal length F6 of the sixth lens, the curvature radius R61 of the object side surface of the sixth lens, and the curvature radius R62 of the image side surface of the sixth lens satisfy: 1.6 mm≤|(R61+R62)*F6 / (R61-R62)|≤3.49 mm.

[0023] In one or more embodiments, the total effective focal length of the fixed-focus lens and half the diagonal length H of the effective pixel area on the imaging plane of the fixed-focus lens satisfy the following: 1.58≤F / H≤1.66.

[0024] In one or more embodiments, the first lens is a glass lens, and the second to sixth lenses are plastic lenses.

[0025] According to the implementation mode of the present application, a fixed-focus lens with a large target surface, low distortion, a large field of view and a miniaturized size is provided. While satisfying the low distortion of an absolute value of distortion less than 1.85% and a total length TTL of an optical system less than 21 mm, a field of view FOV ≥ 63° and a matching target surface of up to 17 mm can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] 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:

[0027] Figure 1 A schematic structural diagram of a fixed-focus lens according to Embodiment 1 of the present application is shown;

[0028] Figure 2 shows an optical distortion curve diagram of the fixed-focus lens in Example 1 of the present application;

[0029] Figure 3 A schematic structural diagram of a fixed-focus lens according to Embodiment 2 of the present application is shown;

[0030] Figure 4 shows an optical distortion curve diagram of the fixed-focus lens in Example 2 of the present application;

[0031] Figure 5 A schematic structural diagram of a fixed-focus lens according to Embodiment 3 of the present application is shown;

[0032] Figure 6 shows an optical distortion curve diagram of the fixed-focus lens in Example 3 of the present application;

[0033] Figure 7 A schematic structural diagram of a fixed-focus lens according to Embodiment 4 of the present application is shown; and

[0034] Figure 8 The optical distortion curve of the fixed-focus lens in Example 4 of the present application is shown. DETAILED DESCRIPTION

[0035] 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 are not intended to limit the scope of the present application in any way. Throughout the specification, the same reference numerals refer to the same elements. The expression "and / or" includes any and all combinations of one or more of the associated listed items.

[0036] 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 first lens.

[0037] In the drawings, the thickness, size and shape of the lenses have been slightly exaggerated for ease of explanation. 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 only examples and are not drawn strictly to scale.

[0038] 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 imaging plane is called the image side of the lens.

[0039] It should also be understood that the terms "comprises", "including", "having", "includes" and / or "comprising", 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 expressions such as "at least one of..." appear after a list of listed features, they modify the entire listed features rather than modifying the individual elements in the list. In addition, when describing embodiments of the present application, "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.

[0040] 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.

[0041] It should be noted that, in the absence of conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The following examples only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for those of ordinary skill in the art, without departing from the concept of the present application, several variations and improvements can also be made, which all belong to the protection scope of the present application.

[0042] The features, principles and other aspects of the present application are described in detail below.

[0043] refer to Figure 1As shown, the fixed-focus lens according to the exemplary embodiment of the present application may include a first lens L1 with positive optical power arranged in sequence from the object side (the side where light is incident) to the image side (the side where light is emitted) along the optical axis, and the object side surface thereof is convex; a second lens L2 with optical power, when the optical power of the second lens L2 is positive, the object side surface thereof is concave, and the image side surface is convex, when the optical power of the second lens L2 is negative, the object side surface thereof is convex, and the image side surface is concave; and a first lens L1 with positive optical power, when the optical power of the second lens L2 is positive, the object side surface thereof is concave, and the image side surface is concave. The third lens L3 has a power, when the third lens L3 has a positive power, its image side surface is convex, and when the third lens L3 has a negative power, its image side surface is concave; the fourth lens L4 has a convex object side surface; the fifth lens L5 has a power, when the fifth lens L5 has a positive power, its object side surface is convex, and when the fifth lens L5 has a negative power, its object side surface is concave; and the sixth lens L6 has a negative power, both the object side surface and the image side surface are concave.

[0044] In an exemplary embodiment, the second lens L2 and the third lens L3 of the fixed focus lens have opposite positive and negative properties of refractive power.

[0045] According to the fixed-focus lens of the implementation mode of the present application, the first lens L1 has positive focal power, and the lens shape is convex toward the object side, which can converge incident light with a large field of view angle into the optical system as much as possible, expand the field of view angle of the optical system, and make the field of view angle FOV ≥ 63°; at the same time, negative distortion can be introduced to effectively balance and correct the distortion generated by the system behind the lens, so as to achieve an absolute value of optical distortion less than or equal to 1.85%.

[0046] According to the fixed-focus lens of the implementation mode of the present application, the second lens L2 may have positive focal power, and the lens shape is a meniscus shape with a convex surface facing the image side. At this time, it is reasonably matched with the third lens L3 having negative focal power and a concave image side shape of the lens, which can effectively control the trend of the incident light of the optical system and raise the light to meet the requirements of a large target surface size; at the same time, more light can enter the optical system, improving the relative illumination of the lens; and it can better balance various aberrations of the optical system, and can effectively correct the optical distortion of the optical system, so that the absolute value of the optical distortion is less than or equal to 1.85%, reducing the degree of deformation of the image, which is beneficial to improving the imaging quality of the optical system.

[0047] According to the fixed-focus lens of the implementation mode of the present application, the second lens L2 may have negative optical power, and the lens shape is a meniscus shape with a concave surface facing the image side. At this time, it is reasonably matched with the third lens L3 having positive optical power and a convex surface on the image side of the lens, which can effectively control the trend of the incident light of the optical system and raise the light to meet the requirements of a large target surface size; at the same time, more light can enter the optical system, improving the relative illumination of the lens; and it can better balance various aberrations of the optical system, and can effectively correct the optical distortion of the optical system, so that the absolute value of the optical distortion is less than or equal to 1.85%, reducing the degree of deformation of the image, which is beneficial to improving the imaging quality of the optical system.

[0048] In an exemplary embodiment, the object side surface of the fourth lens L4 of the fixed focus lens is convex, which can effectively control the trend of light, enable the light to be transmitted smoothly, suppress the generation of astigmatism, and effectively correct the field curvature, thereby greatly improving the imaging performance of the optical system.

[0049] In an exemplary embodiment, the fifth lens L5 may have positive power, and the object side of the lens is convex, which is beneficial to suppressing the generation of astigmatism and effectively correcting the field curvature, thereby improving the imaging quality of the optical system. Moreover, the image side surface of the fifth lens L5 and the image side surface of the first lens L1 may have the same shape, such as both are convex or both are concave. Through reasonable matching, the optical distortion of the optical system can be effectively corrected, the degree of deformation of the image can be reduced, and the imaging quality can be improved.

[0050] In an exemplary embodiment, the fifth lens L5 may have negative optical power, and the object side of the lens is concave, which is beneficial to suppressing the generation of astigmatism and effectively correcting the field curvature, thereby improving the imaging quality of the optical system; and the image side surface of the fifth lens L5 and the image side surface of the first lens L1 may have the same shape, such as both are convex or both are concave. Through reasonable matching, the optical distortion of the optical system can be effectively corrected, the degree of deformation of the image can be reduced, and the imaging quality can be improved.

[0051] In an exemplary embodiment, the sixth lens L6 has negative optical power, and both the object side and the image side of the lens are concave, which is beneficial to controlling the trend of light and raising the light, so that the matching target surface of the optical lens can reach 17 mm; at the same time, it can effectively correct the optical distortion of the off-axis field of view, so that the absolute value of the optical distortion is less than or equal to 1.85%, which is beneficial to reducing the degree of deformation of the image and greatly improving the imaging performance of the optical system.

[0052] In an exemplary embodiment, the fixed focus lens may include an aperture STO, which can effectively converge the light entering the optical system, reduce the maximum aperture of the optical system, and facilitate miniaturization. The aperture STO can be, for example, disposed on the object side of the first lens L1, between the first lens L1 and the second lens L2, or between the second lens L2 and the third lens L3, and the present application does not impose any specific restrictions on its position.

[0053] In an exemplary embodiment, the fixed focus lens may include a protective glass for protecting the photosensitive element. The protective glass may be located between the sixth lens L6 and the imaging plane of the optical system, for example.

[0054] According to the fixed focus lens of the exemplary embodiment of the present application, the following conditional formula can be satisfied: 0.22≤|(R21+R22) / (R31+R32)|≤2.9, wherein R21 is the radius of curvature of the object side of the second lens, R22 is the radius of curvature of the image side of the second lens, R31 is the radius of curvature of the object side of the third lens, and R32 is the radius of curvature of the image side of the third lens. By rationally configuring the radius of curvature of the object side and image side of the second lens and the third lens, the trend of light can be effectively controlled and raised to meet the requirements of a large target surface size, so that the matching target surface can reach 17mm; at the same time, more light can enter the optical system, the relative illumination of the lens is improved, and the relative illumination of the edge is ≥50%.

[0055] In an exemplary embodiment, the first lens L1 can be made of glass, and the other lenses can be made of plastic. The use of a glass-plastic hybrid lens is conducive to reducing the cost of the optical system, and is also conducive to 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; at the same time, the first lens L1 is made of glass, which is conducive to correcting the chromatic aberration of the optical system and improving the color saturation of the lens.

[0056] In an exemplary embodiment, the fixed-focus lens satisfies the following conditional formula: 3.48≤Vd1 / F1≤7.73, where Vd1 is the Abbe number of the first lens L1, and F1 is the effective focal length of the first lens L1. The first lens is made of glass, and by reasonably configuring the ratio of the Abbe number of the first lens to the effective focal length of the first lens, the system chromatic aberration can be effectively corrected, which is beneficial to improving the saturation of the lens color.

[0057] In an exemplary embodiment, the fixed-focus lens satisfies the following conditional formula: 1.80≤F1 / R11≤2.16, where F1 is the effective focal length of the first lens, and R11 is the radius of curvature of the object side of the first lens. By rationally configuring the ratio of the radius of curvature of the object side of the first lens to the effective focal length of the first lens, it is beneficial to converge large-angle light into the optical system, effectively expanding the field of view of the optical system, and making the field of view FOV ≥ 63°; at the same time, negative distortion can be introduced to effectively balance and correct the distortion generated by the system behind the lens, and achieve an absolute value of optical distortion less than or equal to 1.85%.

[0058] In an exemplary embodiment, the fixed-focus lens satisfies the following conditional formula: 1.5≤|F23 / F|≤7.5, where F23 is the combined effective focal length of the second lens and the third lens, and F is the total effective focal length of the fixed-focus lens. By properly configuring the ratio of the combined effective focal length of the second lens and the third lens to the total effective focal length of the fixed-focus lens, the optical distortion of the optical system can be effectively corrected, which is beneficial to reducing the degree of deformation of the image and greatly improving the imaging performance of the optical system.

[0059] In an exemplary embodiment, the fixed-focus lens satisfies the following conditional formula: 12≤|F23 / (d2+d3)|≤32, where F23 is the combined effective focal length of the second lens and the third lens, d2 is the center thickness value of the second lens, and d3 is the center thickness value of the third lens. By rationally configuring the ratio of the combined effective focal length of the second lens and the third lens to the center thickness values ​​of the second lens and the third lens, the light can be smoothly transmitted, the spherical aberration and astigmatism of the optical system can be effectively corrected, and the imaging performance of the optical system can be greatly improved; at the same time, the optical distortion of the optical system can be effectively corrected, so that the absolute value of the optical distortion is less than or equal to 1.85%, which is conducive to reducing the degree of deformation of the image and greatly improving the imaging performance of the optical system.

[0060] In an exemplary embodiment, the fixed focus lens satisfies the following conditional formula: 0.2≤|F4 / (R41+R42)|≤4.3, where F4 is the effective focal length of the fourth lens, R41 is the radius of curvature of the object side surface of the fourth lens, and R42 is the radius of curvature of the image side surface of the fourth lens. By reasonably configuring the effective focal length of the fourth lens and the radius of curvature of the object side surface and the image side surface of the fourth lens, the trend of light can be effectively controlled, so that the light can be smoothly transmitted, the generation of astigmatism can be suppressed, and the field curvature can be effectively corrected, thereby greatly improving the imaging performance of the optical system.

[0061] In an exemplary embodiment, the fixed-focus lens satisfies the following conditional formula: -1.5≤F56 / F≤-0.23, where F56 is the combined effective focal length of the fifth lens and the sixth lens, and F is the total effective focal length of the fixed-focus lens. By reasonably configuring the ratio of the combined effective focal length of the fifth lens and the sixth lens to the total effective focal length of the optical lens, the optical distortion of the off-axis field of view can be effectively corrected, so that the absolute value of the optical distortion is less than or equal to 1.85%, greatly reducing the degree of deformation of the image.

[0062] In an exemplary embodiment, the fixed-focus lens satisfies the following conditional formula: 1≤|(R12+R52) / (R12-R52)|≤7.5, where R12 is the radius of curvature of the image side surface of the first lens, and R52 is the radius of curvature of the image side surface of the fifth lens. By reasonably controlling the radius of curvature of the image side surfaces of the fifth lens and the first lens, and making the shape of the image side surface of the fifth lens the same as that of the image side surface of the first lens, the direction of light can be effectively controlled, and the light can be smoothly transitioned, thereby effectively suppressing the generation of astigmatism; at the same time, negative distortion is introduced to effectively correct the optical distortion of the optical system, reduce the degree of image deformation, and improve the imaging quality.

[0063] In an exemplary embodiment, the fixed-focus lens satisfies the following conditional formula: 1.98≤TTL / H≤2.4, where TTL is the total length of the optical system of the fixed-focus lens, and H is half the diagonal length of the effective pixel area on the imaging surface of the fixed-focus lens. When the system image height is constant, the total length of the optical system of the fixed-focus lens is controlled to be small (TTL<21 mm), which is conducive to miniaturization.

[0064] In an exemplary embodiment, the fixed-focus lens satisfies the following conditional formula: 1.21≤TTL / F≤1.47, where TTL is the total length of the optical system of the fixed-focus lens, and F is the total effective focal length of the fixed-focus lens. When the total effective focal length of the optical system of the fixed-focus lens is constant, by controlling the ratio of the total length of the optical system to the total effective focal length, the total optical length of the system can be reduced, which is conducive to miniaturization of the lens, and the total length of the optical system TTL is less than 21 mm.

[0065] In an exemplary embodiment, the fixed-focus lens satisfies the following conditional formula: 3.62≤CTmax / CTmin≤5.2, where CTmax is the maximum value of the center thickness of each lens in the fixed-focus lens on the optical axis, and CTmin is the minimum value of the center thickness of each lens in the fixed-focus lens on the optical axis. By properly controlling the thickness of each lens of the fixed-focus lens, it is beneficial to stabilize the function of each lens, to minimize the change in light trend at high and low temperatures, and to achieve athermalization of the lens.

[0066] In an exemplary embodiment, the fixed-focus lens satisfies the following condition: 0.7≤d4 / Nd4≤2.1, where d4 is the center thickness value of the fourth lens, and Nd4 is the refractive index of the fourth lens. By properly controlling the center thickness of the fourth lens and the refractive index of the fourth lens, it is helpful to reduce the tolerance sensitivity of the fourth lens and improve the lens production yield.

[0067] In an exemplary embodiment, the fixed-focus lens satisfies the following conditional formula: -3.2≤(R51+R52) / (R51-R52)≤-0.75, where R51 is the radius of curvature of the object side surface of the fifth lens, and R52 is the radius of curvature of the image side surface of the fifth lens. By reasonably configuring the radius of curvature of the object side surface and the image side surface of the fifth lens, the trend of light can be effectively controlled, the deflection angle of the incident light and the outgoing light of the fifth lens can be reduced, the light can smoothly enter the rear of the optical system, the tolerance sensitivity can be reduced, and the lens yield can be improved.

[0068] In an exemplary embodiment, the fixed-focus lens satisfies the following conditional formula: 1.6≤|(R61+R62)*F6 / (R61-R62)|≤3.49, where F6 is the effective focal length of the sixth lens, R61 is the radius of curvature of the object side surface of the sixth lens, and R62 is the radius of curvature of the image side surface of the sixth lens. By reasonably configuring the radius of curvature of the object side surface and the image side surface of the sixth lens and the effective focal length value of the sixth lens, the trend of light can be effectively controlled, the deflection angle of the incident light and the outgoing light of the sixth lens can be reduced, and the light can be smoothly transitioned from the sixth lens to the imaging surface, thereby reducing the tolerance sensitivity of the sixth lens, which is conducive to improving the lens assembly yield.

[0069] In an exemplary embodiment, the fixed-focus lens satisfies the following conditional formula: 1.58≤F / H≤1.66, where F is the total effective focal length of the fixed-focus lens, and H is half of the diagonal length of the effective pixel area on the imaging surface of the fixed-focus lens. When the total effective focal length of the optical system of the fixed-focus lens is constant, the image height of the optical system is optimized to have a larger value, which is conducive to achieving a large target surface, so that half of the diagonal length H of the imaging chip of the fixed-focus lens can reach 8.5 mm.

[0070] 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.

[0071] The fixed-focus lens according to the embodiment of the present application can achieve low distortion, and the absolute value of optical distortion is ≤1.85%.

[0072] The fixed-focus lens according to the embodiment of the present application can be miniaturized, and the total length of the optical system TTL is less than 21 mm.

[0073] The fixed-focus lens according to the implementation mode of the present application can achieve a large target surface, and the matching target surface can reach 17 mm.

[0074] The fixed-focus lens according to the implementation manner of the present application can achieve a large field of view, and the field of view FOV is ≥ 63°.

[0075] The fixed-focus lens according to the embodiments of the present application can achieve an edge relative illumination of ≥50%.

[0076] Specific embodiments of the fixed-focus lens applicable to the above-mentioned embodiments are further described below with reference to the accompanying drawings.

[0077] Example 1

[0078] The following reference Figure 1 and Figure 2 A fixed-focus lens according to Embodiment 1 of the present application is described.

[0079] like Figure 1 As shown, in this embodiment, the fixed-focus lens includes, from the object side to the image side along the optical axis, a first lens L1, an aperture STO, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5 and a sixth lens L6.

[0080] In this embodiment, the first lens L1 has positive power, its object side surface surf1 is convex, and its image side surface surf2 is convex; the second lens L2 has negative power, its object side surface surf4 is convex, and its image side surface surf5 is concave; the third lens L3 has positive power, its object side surface surf6 is concave, and its image side surface surf7 is convex; the fourth lens L4 has positive power, its object side surface surf8 is convex, and its image side surface surf9 is convex; the fifth lens L5 has negative power, its object side surface surf10 is concave, and its image side surface surf11 is convex; the sixth lens L6 has negative power, its object side surface surf12 is concave, and its image side surface surf13 is concave. The protective glass CG has an object side surface surf14 and an image side surface surf15. Light incident from the object side passes through the surfaces of each optical element in sequence and is finally imaged on the imaging surface (IMA) surf16.

[0081] In this embodiment, the first lens L1 is made of glass, and the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5 and the sixth lens L6 are all made of plastic.

[0082] Table 1 shows some basic parameters of each lens of the fixed focus lens of this embodiment, including surface type, curvature radius, thickness, refractive index of the material, and Abbe number, wherein the units of curvature radius and thickness / distance are all millimeters (mm).

[0083] Face number Surface type Radius of curvature Thickness Refractive Index Abbe number surf1 Aspheric 5.729 3.197 1.50 81.56 surf2 Aspheric -1768.041 0.697 surf3(STO) Spherical endless -0.088 surf4 Aspheric 12.835 0.823 1.64 23.53 surf5 Aspheric 7.278 1.618 surf6 Aspheric -48.585 1.371 1.64 23.53 surf7 Aspheric -25.779 0.796 surf8 Aspheric 45.848 2.637 1.54 55.71 surf9 Aspheric -7.480 0.200 surf10 Aspheric -8.644 2.298 1.64 23.53 surf11 Aspheric -18.584 1.014 surf12 Aspheric -11.796 1.503 1.54 55.71 surf13 Aspheric 7.859 0.702 surf14 Spherical Infinity 0.300 1.52 64.20 surf15 Spherical endless 0.200 surf16(IMA) Spherical endless 0.000

[0084] Table 1

[0085] In this embodiment, the object side surface and the image side surface of each lens of the fixed focus lens from the first lens L1 to the sixth lens L6 are all aspherical surfaces, and the surface shape x of each aspherical lens can be defined by but not limited to the following aspherical surface formula:

[0086]

[0087] 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 inverse of the curvature radius R in Table 1 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 coefficients A4, A6, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, A18, A19, A20, A21, A22, A23, A24, A25, A26, A27, A28, A29, A30, A31, A32, A33, A34, A35, A36, A37, A38, 10 , A 12 , A 14 and A 16 .

[0088]

[0089]

[0090] Table 2

[0091] The aperture coefficient FNO of the fixed-focus lens of this embodiment is 2.2, and the field of view FOV is 63°.

[0092] 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 0.86%. 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.

[0093] Example 2

[0094] The following reference Figure 3 to Figure 4 A fixed-focus lens according to Embodiment 2 of the present application is described. In Embodiment 2 and the following embodiments, for the sake of brevity, some descriptions similar to Embodiment 1 will be omitted.

[0095] like Figure 3As shown, in this embodiment, the fixed-focus lens includes, from the object side to the image side along the optical axis, an aperture STO, a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5 and a sixth lens L6.

[0096] In this embodiment, the first lens L1 has positive power, its object side surface surf2 is convex, and its image side surface surf3 is concave; the second lens L2 has positive power, its object side surface surf4 is concave, and its image side surface surf5 is convex; the third lens L3 has negative power, its object side surface surf6 is concave, and its image side surface surf7 is concave; the fourth lens L4 has positive power, its object side surface surf8 is convex, and its image side surface surf9 is convex; the fifth lens L5 has positive power, its object side surface surf10 is convex, and its image side surface surf11 is concave; the sixth lens L6 has negative power, its object side surface surf12 is concave, and its image side surface surf13 is concave. The protective glass CG has an object side surface surf14 and an image side surface surf15. Light incident from the object side passes through the surfaces of each optical element in sequence and is finally imaged on the imaging surface (IMA) surf16.

[0097] In this embodiment, the first lens L1 is made of glass, and the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5 and the sixth lens L6 are all made of plastic.

[0098] Table 3 shows some basic parameters of each lens of the fixed focus lens of this embodiment, including surface type, curvature radius, thickness, refractive index of material, and Abbe number, wherein the units of curvature radius and thickness / distance are all millimeters (mm).

[0099]

[0100]

[0101] Table 3

[0102] In this embodiment, the object-side surface and the image-side surface of the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5 and the sixth lens L6 are all aspherical surfaces, and the surface shape of each aspherical lens can be defined by formula (1) given in the above embodiment 1.

[0103] Table 4 shows the cone coefficient (k) and the high-order coefficients A4, A6, A8, A 10 , A 12 , A 14 and A 16 .

[0104] Face number / coefficient k A4 A6 A8 A10 A12 A14 A16 surf4 90.00 -8.97E-04 1.43E-05 1.02E-06 -9.02E-08 2.12E-09 0.00E+00 0.00E+00 surf5 -34.98 -1.97E-03 2.81E-05 3.59E-07 -7.68E-08 -2.77E-09 0.00E+00 0.00E+00 surf6 38.71 1.75E-03 -5.39E-05 6.02E-07 2.38E-07 -1.25E-08 0.00E+00 0.00E+00 surf7 -99.47 2.67E-03 -7.04E-05 2.79E-06 6.06E-08 4.91E-09 0.00E+00 0.00E+00 surf8 -117.28 -1.40E-03 -4.83E-05 2.12E-06 -3.97E-07 1.43E-08 0.00E+00 0.00E+00 surf9 47.23 -1.89E-03 -7.65E-06 8.38E-07 -6.05E-08 1.65E-09 0.00E+00 0.00E+00 surf10 -25.17 -1.00E-03 -4.05E-05 -2.18E-07 3.19E-08 -3.87E-10 0.00E+00 0.00E+00 surf11 0.00 3.90E-04 -4.57E-05 9.78E-07 -9.45E-09 1.12E-11 0.00E+00 0.00E+00 surf12 -0.45 -5.07E-04 4.16E-05 -5.37E-07 2.55E-09 -9.14E-12 0.00E+00 0.00E+00 surf13 -65.21 -6.41E-04 2.42E-05 -8.39E-07 1.34E-08 -7.12E-11 0.00E+00 0.00E+00

[0105] Table 4

[0106] The aperture coefficient FNO of the fixed-focus lens of this embodiment is 2.2, and the field of view FOV is 64°.

[0107] 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 1.85%. 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.

[0108] Example 3

[0109] The following reference Figures 5 and 6 A fixed-focus lens according to Embodiment 3 of the present application is described.

[0110] like Figure 5 As shown, in this embodiment, the fixed-focus lens includes, from the object side to the image side along the optical axis, a first lens L1, an aperture STO, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5 and a sixth lens L6.

[0111] In this embodiment, the first lens L1 has positive power, its object side surface surf1 is convex, and its image side surface surf2 is convex; the second lens L2 has negative power, its object side surface surf4 is convex, and its image side surface surf5 is concave; the third lens L3 has positive power, its object side surface surf6 is convex, and its image side surface surf7 is convex; the fourth lens L4 has negative power, its object side surface surf8 is convex, and its image side surface surf9 is concave; the fifth lens L5 has positive power, its object side surface surf10 is convex, and its image side surface surf11 is convex; the sixth lens L6 has negative power, its object side surface surf12 is concave, and its image side surface surf13 is concave. The protective glass CG has an object side surface surf14 and an image side surface surf15. Light incident from the object side passes through the surfaces of each optical element in sequence and is finally imaged on the imaging surface (IMA) surf16.

[0112] In this embodiment, the first lens L1 is made of glass, and the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5 and the sixth lens L6 are all made of plastic.

[0113] Table 5 shows some basic parameters of each lens of the fixed focus lens of this embodiment, including surface type, curvature radius, thickness, refractive index of material, and Abbe number, wherein the units of curvature radius and thickness / distance are all millimeters (mm).

[0114] Face number Surface type Radius of curvature thickness Refractive Index Abbe number surf1 Spherical 7.106 3.000 1.49 70.44 surf2 Spherical -235.756 0.194 surf3(STO) Spherical endless 0.100 surf4 Aspheric 15.004 0.960 1.66 20.38 surf5 Aspheric 8.863 1.286 surf6 Aspheric 75.975 2.315 1.54 55.71 surf7 Aspheric -17.708 1.008 surf8 Aspheric 51.201 1.143 1.61 25.58 surf9 Aspheric 19.454 0.233 surf10 Aspheric 14.905 3.500 1.54 55.71 surf11 Aspheric -263.357 2.000 surf12 Aspheric -8.403 1.486 1.54 55.71 surf13 Aspheric 12.123 0.502 surf14 Spherical endless 0.300 1.52 64.20 surf15 Spherical endless 0.200 surf16(IMA) Spherical endless 0.000

[0115] Table 5

[0116] In this embodiment, the object-side surface and the image-side surface of the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5 and the sixth lens L6 are all aspherical surfaces, and the surface shape of each aspherical lens can be defined by formula (1) given in the above embodiment 1.

[0117] Table 6 shows the cone coefficient (k) and the high-order coefficients A4, A6, A8, A 10 , A 12 , A 14 and A 16 .

[0118] Face number / coefficient k A4 A6 A8 A10 A12 A14 A16 surf4 6.24 -1.89E-03 2.28E-06 6.94E-07 0.00E+00 0.00E+00 0.00E+00 0.00E+00 surf5 3.14 -2.41E-03 -1.99E-05 2.11E-07 0.00E+00 0.00E+00 0.00E+00 0.00E+00 surf6 -60.50 -8.39E-04 -3.66E-05 -2.81E-06 0.00E+00 0.00E+00 0.00E+00 0.00E+00 surf7 14.55 -1.99E-03 5.80E-06 -8.55E-07 0.00E+00 0.00E+00 0.00E+00 0.00E+00 surf8 -46.42 -2.75E-03 -8.26E-06 7.20E-07 0.00E+00 0.00E+00 0.00E+00 0.00E+00 surf9 13.13 -2.43E-03 -8.88E-06 9.38E-07 0.00E+00 0.00E+00 0.00E+00 0.00E+00 surf10 -4.28 -1.09E-03 -2.51E-05 4.31E-08 0.00E+00 0.00E+00 0.00E+00 0.00E+00 surf11 -16.56 4.83E-04 -3.29E-05 2.67E-07 0.00E+00 0.00E+00 0.00E+00 0.00E+00 surf12 -0.71 -1.09E-03 3.17E-05 -1.13E-07 0.00E+00 0.00E+00 0.00E+00 0.00E+00 surf13 -66.79 -1.44E-04 -7.65E-06 1.00E-07 0.00E+00 0.00E+00 0.00E+00 0.00E+00

[0119] Table 6

[0120] The aperture coefficient FNO of the fixed-focus lens of this embodiment is 2.2, and the field of view FOV is 63°.

[0121] 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 1.34%. 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.

[0122] Example 4

[0123] The following reference Figures 7 and 8 A fixed-focus lens according to Embodiment 4 of the present application is described.

[0124] like Figure 7 As shown, in this embodiment, the fixed-focus lens includes, from the object side to the image side along the optical axis, a first lens L1, a second lens L2, an aperture STO, a third lens L3, a fourth lens L4, a fifth lens L5 and a sixth lens L6.

[0125] In this embodiment, the first lens L1 has positive power, its object side surface surf1 is convex, and its image side surface surf2 is concave; the second lens L2 has negative power, its object side surface surf3 is convex, and its image side surface surf4 is concave; the third lens L3 has positive power, its object side surface surf6 is convex, and its image side surface surf7 is convex; the fourth lens L4 has positive power, its object side surface surf8 is convex, and its image side surface surf9 is concave; the fifth lens L5 has positive power, its object side surface surf10 is convex, and its image side surface surf11 is concave; the sixth lens L6 has negative power, its object side surface surf12 is concave, and its image side surface surf13 is concave. The protective glass CG has an object side surface surf14 and an image side surface surf15. Light incident from the object side passes through the surfaces of each optical element in sequence and is finally imaged on the imaging surface (IMA) surf16.

[0126] In this embodiment, the first lens L1 is made of glass, and the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5 and the sixth lens L6 are all made of plastic.

[0127] Table 7 shows some basic parameters of each lens of the fixed focus lens of this embodiment, including surface type, radius of curvature, thickness, refractive index of material, and Abbe number, wherein the units of radius of curvature and thickness / distance are all millimeters (mm).

[0128] Face number Surface type Radius of curvature thickness Refractive Index Abbe number surf1 Spherical 8.150 2.514 1.57 62.96 surf2 Spherical 99.266 0.314 surf3 Aspheric 10.331 0.692 1.64 23.53 surf4 Aspheric 6.283 0.717 surf5(STO) Aspheric endless 0.100 surf6 Aspheric 108.744 2.942 1.54 55.71 surf7 Spherical -39.763 1.152 surf8 Spherical 8.380 1.421 1.54 55.71 surf9 Spherical 13.998 1.210 surf10 Aspheric 12.175 2.286 1.54 55.71 surf11 Aspheric 34.286 2.000 surf12 Aspheric -10.391 2.738 1.64 23.53 surf13 Aspheric 16.682 0.501 surf14 Spherical endless 0.300 1.52 64.20 surf15 Spherical endless 0.200 surf16(IMA) Spherical endless 0.000

[0129] Table 7

[0130] In this embodiment, the object-side surface and the image-side surface of the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5 and the sixth lens L6 are all aspherical surfaces, and the surface shape of each aspherical lens can be defined by formula (1) given in the above embodiment 1.

[0131] Table 8 shows the cone coefficient (k) and the high-order coefficients A4, A6, A8, A 10 , A 12 , A 14 and A 16 .

[0132]

[0133]

[0134] Table 8

[0135] The aperture coefficient FNO of the fixed-focus lens of this embodiment is 2.2, and the field of view FOV is 63°.

[0136] Figure 8The optical distortion curve of the fixed-focus lens of Example 4 is shown, and the maximum absolute value of the optical distortion is 1.48%. 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.

[0137] In summary, the fixed-focus lenses in the above-mentioned Embodiments 1 to 4 respectively satisfy the conditional expressions shown in Table 9 below.

[0138] Conditional / Example 1 2 3 4 3.48≤Vd1 / F1≤7.73 7.12 6.96 4.97 4.09 1.8≤F1 / R11≤2.16 2.00 2.01 1.99 1.89 1.5≤|F23 / F|≤7.5 3.11 1.57 7.16 3.90 12≤|F23 / (d2+d3)|≤32 19.83 12.33 30.75 15.13 0.22≤|(R21+R22) / (R31+R32)|≤2.9 0.27 97.01 0.41 0.24 0.2≤|F4 / (R41+R42)|≤4.3 0.32 4.26 0.73 1.59 -1.5≤F56 / F≤-0.23 -0.42 -0.93 -1.32 -1.17 1≤|(R12+R52) / (R12-R52)|≤7.5 1.02 1.04 18.08 2.06 1.98≤TTL / H≤2.4 2.03 2.02 2.14 2.24 1.21≤TTL / F≤1.47 1.24 1.24 1.30 1.35 3.62≤CTmax / CTmin≤5.2 3.86 4.95 3.64 4.25 0.7≤d4 / Nd4≤2.1 1.72 1.95 0.71 0.93 -3.2≤(R51+R52) / (R51-R52)≤-0.75 -2.74 -3.08 -0.89 -2.10 1.6mm≤|(R61+R62)*F6 / (R61-R62)|≤3.49mm 1.71 2.98 1.63 2.21 1.58≤F / H≤1.66 1.64 1.64 1.66 1.66

[0139] Table 9

[0140] According to the fixed-focus lens provided in the embodiment of the present application, by reasonably setting the surface shape and optical focal length distribution of each lens, the trend of the incident light of the optical system can be effectively controlled, and the light can be raised to meet the target surface size requirement and the target surface matching requirement of 17 mm; the incident light with a large field of view angle can be gathered as much as possible into the optical system, and the field of view angle of the optical system is expanded to make the field of view angle FOV ≥ 63°; at the same time, various aberrations of the optical system can be well balanced, and the optical distortion of the optical system can be effectively corrected to make the absolute value of the optical distortion less than or equal to 1.85%, thereby reducing the degree of deformation of the image; at the same time, miniaturization can be achieved, and the total length of the optical system TTL is less than 21 mm.

[0141] 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: A first lens having positive optical power, whose object side surface is convex; a second lens having an optical power, wherein when the optical power of the second lens is positive, the object side surface thereof is concave, and the image side surface thereof is convex; and when the optical power of the second lens is negative, the object side surface thereof is convex, and the image side surface thereof is concave; a third lens having an optical power, wherein when the optical power of the third lens is positive, the image side surface thereof is a convex surface; and when the optical power of the third lens is negative, the image side surface thereof is a concave surface; The fourth lens has a convex object side surface; a fifth lens having an optical power, wherein when the optical power of the fifth lens is positive, the object side surface thereof is a convex surface; and when the optical power of the fifth lens is negative, the object side surface thereof is a concave surface; and The sixth lens with negative optical power has concave object-side and image-side surfaces. Among them, the positive and negative properties of the optical power of the second lens and the third lens are opposite; the image side surface of the first lens and the image side surface of the fifth lens are both convex or both concave; and the curvature radius R21 of the object side surface of the second lens, the curvature radius R22 of the image side surface of the second lens, the curvature radius R31 of the object side surface of the third lens, and the curvature radius R32 of the image side surface of the third lens satisfy: 0.22≤|(R21+R22) / (R31+R32)|≤2.

9.

2. The fixed-focus lens according to claim 1, wherein: The Abbe number Vd1 of the first lens and the effective focal length F1 of the first lens satisfy: 3.48≤Vd1 / F1≤7.

73.

3. The fixed-focus lens according to claim 1, wherein: The effective focal length F1 of the first lens and the curvature radius R11 of the object-side surface of the first lens satisfy: 1.80≤F1 / R11≤2.

16.

4. The fixed-focus lens according to claim 1, wherein: The combined effective focal length F23 of the second lens and the third lens and the total effective focal length F of the fixed-focus lens satisfy the following: 1.5≤|F23 / F|≤7.

5.

5. The fixed-focus lens according to claim 1, wherein: The combined effective focal length of the second lens and the third lens, the center thickness value d2 of the second lens, and the center thickness value d3 of the third lens satisfy: 12≤|F23 / (d2+d3)|≤32.

6. The fixed-focus lens according to claim 1, wherein: An effective focal length F4 of the fourth lens, a curvature radius R41 of the object-side surface of the fourth lens, and a curvature radius R42 of the image-side surface of the fourth lens satisfy: 0.2≤|F4 / (R41+R42)|≤4.

3.

7. The fixed-focus lens according to claim 1, wherein: The combined effective focal length F56 of the fifth lens and the sixth lens and the total effective focal length F of the fixed-focus lens satisfy the following: -1.5≤F56 / F≤-0.

23.

8. The fixed-focus lens according to claim 1, wherein: A curvature radius R12 of the image side surface of the first lens and a curvature radius R52 of the image side surface of the fifth lens satisfy: 1≤|(R12+R52) / (R12-R52)|≤7.

5.

9. The fixed-focus lens according to claim 1, wherein: The total length TTL of the optical system of the fixed-focus lens and half the diagonal length H of the effective pixel area on the imaging surface of the fixed-focus lens satisfy the following: 1.98≤TTL / H≤2.

4.

10. The fixed-focus lens according to claim 1, wherein: The total length TTL of the optical system of the fixed-focus lens and the total effective focal length F of the fixed-focus lens satisfy the following: 1.21≤TTL / F≤1.47.

Images