Optical imaging system

Abstract

The application discloses an optical imaging system, which comprises, in sequence from the object side to the image side along the optical axis, a first lens, a second lens, a third lens and a fourth lens. The first lens has positive focal power, the object side surface is a convex surface, and the image side surface is a concave surface. The second lens has positive focal power, the object side surface is a convex surface, and the image side surface is a concave surface. The third lens has negative focal power, and the image side surface is a concave surface. The fourth lens has positive focal power. The first lens is made of glass, the refractive index is greater than 1.85, and the surface types of the object side surface and the image side surface are both spherical surfaces. The effective focal length f of the optical imaging system and the maximum field angle FOV of the optical imaging system satisfy 24mm < f / tan(FOV) < 26mm.

Description

Technical Field

[0001] This application relates to the field of optical components, and more specifically, to an optical imaging system. Background Technology

[0002] With the development of smartphones, people have increasingly higher demands for mobile phone lenses and greater zoom capabilities. To enable mobile phones to have a wider zoom range, it is necessary to introduce periscope telephoto lenses. Currently, periscope telephoto lenses on the market add a triangular prism at the front of the lens to refract light, while the lens lies flat inside the phone. However, this design makes the prism shape easily visible to consumers, affecting the phone's aesthetics. In addition, how to make periscope telephoto lenses meet the requirements of telephoto shooting while also having low temperature drift, good assembly stability, and low system aberrations has always been a hot research topic in the field. Summary of the Invention

[0003] This application provides an optical imaging system comprising, along the optical axis from the object side to the image side, a first lens, a second lens, a third lens, and a fourth lens; wherein the first lens has positive optical power, its object side is convex, and its image side is concave; the second lens has positive optical power, its object side is convex, and its image side is concave; the third lens has negative optical power, and its image side is concave; the fourth lens has positive optical power; the first lens is made of glass with a refractive index greater than 1.85, and both its object side and image side are spherical; and the effective focal length f of the optical imaging system and the maximum field of view (FOV) of the optical imaging system satisfy: 24mm. <f / tan(FOV)<26mm。

[0004] In one embodiment, the effective focal length f1 of the first lens and the effective focal length f of the optical imaging system satisfy: 3.1 < (f + f1) / (f - f1) < 3.6.

[0005] In one embodiment, the effective focal length f3 of the third lens and the effective focal length f4 of the fourth lens satisfy: 1.7 < (f4-f3) / (f4+f3) < 2.6.

[0006] In one embodiment, the radius of curvature R1 of the object side surface of the first lens, the radius of curvature R3 of the object side surface of the second lens, the refractive index N1 of the first lens, and the refractive index N2 of the second lens satisfy: 3.6mm < (R1+R3) / (N1+N2) < 4.4mm.

[0007] In one embodiment, the radius of curvature R1 of the object side of the first lens, the radius of curvature R6 of the image side of the third lens, the refractive index N1 of the first lens, and the refractive index N3 of the third lens satisfy: 2.6mm < (R1 + R6) / (N1 + N3) < 3.3mm.

[0008] In one embodiment, the radius of curvature R4 of the image-side surface of the second lens, the radius of curvature R8 of the image-side surface of the fourth lens, and the effective focal length f of the optical imaging system satisfy: 0.9 < (R4 - R8) / f < 1.7.

[0009] In one embodiment, the effective focal length f of the optical imaging system and the distance TD along the optical axis from the object-side surface of the first lens to the image-side surface of the fourth lens satisfy: 3.3 <f / TD<3.7。

[0010] In one embodiment, the combined focal length f12 of the first lens and the second lens, the center thickness CT1 of the first lens on the optical axis, and the center thickness CT2 of the second lens on the optical axis satisfy: 3.0 <f12 / (CT1+CT2)<3.8。

[0011] In one embodiment, the effective half-aperture DT41 of the object side of the fourth lens, the effective half-aperture DT42 of the image side of the fourth lens, and the effective half-aperture DT12 of the image side of the first lens satisfy: 1.4 < (DT41 + DT42) / DT12 < 1.6.

[0012] In one embodiment, the combined focal length f34 of the third lens and the fourth lens, the edge thickness ET3 of the third lens, and the edge thickness ET4 of the fourth lens satisfy: -11 <f34 / (ET3+ET4)<-6。

[0013] In one embodiment, the edge thickness ET1 of the first lens, the edge thickness ET2 of the second lens, and the air gap T23 between the second lens and the third lens on the optical axis satisfy: 1.5 < (ET1 + ET2) / T23 < 2.9.

[0014] In one embodiment, the edge thickness ET3 of the third lens, the center thickness CT3 of the third lens on the optical axis, and the air gap T34 between the third and fourth lenses on the optical axis satisfy: 0.8 <ET3 / (CT3+T34)<1.2。

[0015] The optical imaging system proposed in this application rationally combines the optical power, surface type, and material of the lenses, and simultaneously controls the relationship between the effective focal length and the maximum field angle of the optical imaging system, so that the optical imaging system has the characteristics of long focal length, small temperature drift, good assembly stability, and small system aberration. Specifically, the first lens, the second lens, the third lens, and the fourth lens are distributed according to the optical power of positive, positive, negative, and positive respectively, which can reduce the system aberration and improve the imaging quality of the optical imaging system; the first lens is made of glass material with a refractive index greater than 1.85, which is beneficial to effectively control the temperature drift change and chromatic aberration, and at the same time ensure high performance; the surface types of the object side and the image side of the first lens are both spherical surfaces, which is beneficial to ensure the processing requirements of the first lens; satisfying 24mm < f / tan(FOV) < 26mm can make the optical power distribution of the lens more reasonable, effectively balance the aberration, improve the resolution of the lens, and also help to improve the stability of lens assembly, and can better achieve the long focal length design. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Other features, objects, and advantages of this application will become more apparent by reading the detailed description of the non-limiting embodiments made with reference to the following drawings:

[0017] Figure 1 FIG. shows a schematic structural diagram of the optical imaging system according to Embodiment 1 of this application;

[0018] Figures 2A to 2D FIGS. respectively show the axial chromatic aberration curve, astigmatism curve, distortion curve, and lateral chromatic aberration curve of the optical imaging system of Embodiment 1;

[0019] Figure 3 FIG. shows a schematic structural diagram of the optical imaging system according to Embodiment 2 of this application;

[0020] Figures 4A to 4D FIGS. respectively show the axial chromatic aberration curve, astigmatism curve, distortion curve, and lateral chromatic aberration curve of the optical imaging system of Embodiment 2;

[0021] Figure 5 FIG. shows a schematic structural diagram of the optical imaging system according to Embodiment 3 of this application;

[0022] Figures 6A to 6D FIGS. respectively show the axial chromatic aberration curve, astigmatism curve, distortion curve, and lateral chromatic aberration curve of the optical imaging system of Embodiment 3;

[0023] Figure 7 FIG. shows a schematic structural diagram of the optical imaging system according to Embodiment 4 of this application; and

[0024] Figures 8A to 8DThe on-axis chromatic aberration curve, astigmatism curve, distortion curve, and magnification chromatic aberration curve of the optical imaging system of Example 4 are shown respectively. Detailed Implementation

[0025] 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. The expression "and / or" includes any and all combinations of one or more of the associated listed items.

[0026] 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.

[0027] 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 strictly to scale.

[0028] 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 imaging plane is called the image-side surface of the lens.

[0029] It should also be understood that the terms "comprising," "including," "having," "containing," 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. Furthermore, when expressions such as "at least one of..." appear after a list of listed features, they modify the entire list of features, not individual elements in the list. Additionally, 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.

[0030] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. It should also be understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0031] It should be noted that, without conflict, the embodiments in this application and the features in the embodiments may be combined with each other. The following will detail this application by referring to the drawings and in combination with the embodiments.

[0032] The features, principles, and other aspects of this application will be described in detail below.

[0033] The optical imaging system according to an exemplary embodiment of this application may include four lenses with optical power, namely, a first lens, a second lens, a third lens, and a fourth lens arranged in sequence from the object side to the image side along the optical axis. Among them, the first lens has a positive optical power, its object side surface is convex, and its image side surface is concave; the second lens has a positive optical power, its object side surface is convex, and its image side surface is concave; the third lens has a negative optical power, and its image side surface is concave; the fourth lens has a positive optical power; the first lens is made of glass, its refractive index is greater than 1.85, and the surface profiles of both the object side surface and the image side surface are spherical surfaces. The effective focal length f of the optical imaging system and the maximum field angle FOV of the optical imaging system satisfy: 24 mm < f / tan(FOV) < 26 mm. Setting the first lens to have a positive optical power, with its object side surface convex and its image side surface concave, is beneficial to reducing the temperature drift change amount and is also beneficial to adding a retaining ring structure on the object side surface of the first lens to ensure the assembly stability and reliability of the optical imaging system; setting the object side surface of the second lens to be convex and the image side surface to be concave is beneficial to adding a thick spacer structure between the first lens and the second lens to ensure the assembly stability; the first lens, the second lens, the third lens, and the fourth lens are respectively distributed with positive, positive, negative, and positive optical powers, which can reduce the system aberration and improve the imaging quality of the optical imaging system; the first lens is made of glass with a refractive index greater than 1.85, which is beneficial to effectively controlling the temperature drift change amount and chromatic aberration while ensuring high performance; the surface profiles of both the object side surface and the image side surface of the first lens are spherical surfaces, which is beneficial to ensuring the processing requirements of the first lens; controlling the relationship between the optical powers, surface profiles of each lens, and the effective focal length f of the optical imaging system and the maximum field angle FOV of the optical imaging system can make the optical power distribution of the lens more reasonable, effectively balance the aberration, improve the resolution of the lens, and also help to improve the stability of lens assembly, and can better achieve the long focal length design.

[0034] In an exemplary embodiment, the optical imaging system according to an exemplary embodiment of this application further includes an aperture disposed on the object side surface of the first lens.

[0035] In an exemplary embodiment, the optical imaging system according to this application satisfies: 3.1 < (f + f1) / (f - f1) < 3.6, where f1 is the effective focal length of the first lens and f is the effective focal length of the optical imaging system. Satisfying 3.1 < (f + f1) / (f - f1) < 3.6, by controlling the effective focal length of the first lens, facilitates a reasonable spatial distribution of the optical power of the first lens, thereby reducing lens aberrations; simultaneously, it optimizes the temperature drift variation of the system's focal length.

[0036] In an exemplary embodiment, the optical imaging system according to this application satisfies: 1.7 < (f4 - f3) / (f4 + f3) < 2.6, where f3 is the effective focal length of the third lens and f4 is the effective focal length of the fourth lens. Satisfying 1.7 < (f4 - f3) / (f4 + f3) < 2.6, by controlling the focal length ratio of the third and fourth lenses, facilitates a reasonable spatial distribution of the optical power of the third and fourth lenses, thereby reducing lens aberrations.

[0037] In an exemplary embodiment, the optical imaging system according to this application satisfies the following condition: 3.6mm < (R1+R3) / (N1+N2) < 4.4mm, where R1 is the radius of curvature of the object-side surface of the first lens, R3 is the radius of curvature of the object-side surface of the second lens, N1 is the refractive index of the first lens, and N2 is the refractive index of the second lens. By controlling the radius of curvature of the object-side surfaces of the first and second lenses, the shapes of the first and second lenses can be controlled to meet manufacturability requirements. A pressure ring needs to be placed on the object-side surface of the first lens, and the radius of curvature requires close attention. Simultaneously, controlling the refractive indices of the first and second lenses can improve the overall image quality of the optical imaging system and reduce the temperature drift variation of the optical imaging system.

[0038] In an exemplary embodiment, the optical imaging system according to this application satisfies the following condition: 2.6mm < (R1 + R6) / (N1 + N3) < 3.3mm, where R1 is the radius of curvature of the object-side surface of the first lens, R6 is the radius of curvature of the image-side surface of the third lens, N1 is the refractive index of the first lens, and N3 is the refractive index of the third lens. Satisfying 2.6mm < (R1 + R6) / (N1 + N3) < 3.3mm, by controlling the radius of curvature of the object-side surface of the first lens and the radius of curvature of the image-side surface of the third lens, facilitates control over the lens shapes of the first and third lenses, meeting manufacturability requirements. Simultaneously, controlling the refractive indices of the first and third lenses optimizes performance while meeting temperature drift requirements.

[0039] In an exemplary embodiment, the optical imaging system according to the present application may satisfy: 0.9 < (R4 - R8) / f < 1.7, where R4 is the radius of curvature of the image side of the second lens, R8 is the radius of curvature of the image side of the fourth lens, and f is the effective focal length of the optical imaging system. Satisfying 0.9 < (R4 - R8) / f < 1.7 is conducive to controlling the shapes of the second lens and the fourth lens by controlling the radii of curvature of the image sides of the second lens and the fourth lens, meeting the processing requirements, and at the same time controlling the effective focal length of the optical imaging system to meet the performance requirements and the overall machine size requirements.

[0040] In an exemplary embodiment, the optical imaging system according to the present application may satisfy: 3.3 < f / TD < 3.7, where f is the effective focal length of the optical imaging system, and TD is the distance on the optical axis from the object side of the first lens to the image side of the fourth lens. Satisfying 3.3 < f / TD < 3.7 can ensure the height requirement of the lens barrel by controlling the axial distance from the object side of the first lens to the image side of the fourth lens, thereby ensuring the feasibility of the upright assembly of the lens.

[0041] In an exemplary embodiment, the optical imaging system according to the present application may satisfy: 3.0 < f12 / (CT1 + CT2) < 3.8, where f12 is the combined focal length of the first lens and the second lens, CT1 is the central thickness of the first lens on the optical axis, and CT2 is the central thickness of the second lens on the optical axis. Satisfying 3.0 < f12 / (CT1 + CT2) < 3.8 is conducive to the reasonable distribution of the optical powers of the first lens and the second lens in space by controlling the combined focal length of the first lens and the second lens, thereby reducing the aberration of the optical imaging system. Controlling the central thicknesses of the first lens and the second lens on the optical axis can ensure the processability of the first lens and the second lens.

[0042] In an exemplary embodiment, the optical imaging system according to the present application may satisfy: 1.4 < (DT41 + DT42) / DT12 < 1.6, where DT41 is the effective semi-aperture of the object side of the fourth lens, DT42 is the effective semi-aperture of the image side of the fourth lens, and DT12 is the effective semi-aperture of the image side of the first lens. Satisfying 1.4 < (DT41 + DT42) / DT12 < 1.6 can effectively control the aperture size of the optical imaging system, control the light passing amount of the system, and meet the F-number requirement by controlling the effective apertures of the object side and the image side of the fourth lens and the effective semi-aperture of the image side of the first lens.

[0043] In an exemplary embodiment, the optical imaging system according to the present application may satisfy: -11 < f34 / (ET3 + ET4) < -6, where f34 is the combined focal length of the third lens and the fourth lens, ET3 is the edge thickness of the third lens, and ET4 is the edge thickness of the fourth lens. Satisfying -11 < f34 / (ET3 + ET4) < -6 is conducive to the reasonable spatial distribution of the optical power of the first lens and the second lens by controlling the combined focal length of the third lens and the fourth lens, thereby reducing the aberration of the optical imaging system. By controlling the edge thicknesses of the third lens and the fourth lens, the processing requirements of the third lens and the fourth lens can be ensured.

[0044] In an exemplary embodiment, the optical imaging system according to the present application may satisfy: 1.5 < (ET1 + ET2) / T23 < 2.9, where ET1 is the edge thickness of the first lens, ET2 is the edge thickness of the second lens, and T23 is the air gap on the optical axis between the second lens and the third lens. Satisfying 1.5 < (ET1 + ET2) / T23 < 2.9 can meet the processing requirements of the optical imaging system by controlling the edge thicknesses of the first lens and the second lens and the air gap on the optical axis between the second lens and the third lens.

[0045] In an exemplary embodiment, the optical imaging system according to the present application may satisfy: 0.8 < ET3 / (CT3 + T34) < 1.2, where ET3 is the edge thickness of the third lens, CT3 is the central thickness of the third lens on the optical axis, and T34 is the air gap on the optical axis between the third lens and the fourth lens. Satisfying 0.8 < ET3 / (CT3 + T34) < 1.2 ensures the processing requirements of the third lens while meeting the assembly stability requirements between the third lens and the fourth lens by controlling the edge thickness of the third lens, the central thickness of the third lens on the optical axis, and the air gap on the optical axis between the third lens and the fourth lens.

[0046] In an exemplary embodiment, the first lens to the fourth lens include spherical lenses and aspherical lenses. Exemplarily, the object side and the image side of the first lens are spherical surfaces, and at least one of the mirror surfaces of each of the second lens to the fourth lens is an aspherical mirror surface. Optionally, the object side and the image side of each of the second lens to the fourth lens are both aspherical mirror surfaces. The present application does not specifically limit the specific number of spherical lenses and aspherical lenses. When focusing on the resolution quality, aspherical lenses can be used for all lenses. The characteristics of an aspherical lens are that the curvature changes continuously from the center of the lens to the periphery of the lens. The characteristics of a spherical lens are that it has a constant curvature from the center to the periphery of the lens. Aspherical lenses have better curvature radius characteristics and have the advantages of improving distortion aberration and astigmatism aberration. After using aspherical lenses, it is possible to eliminate the aberration that appears during imaging as much as possible, thereby improving the imaging quality.

[0047] In an exemplary embodiment, the first lens is a glass lens, which is beneficial for balancing performance, temperature drift, and chromatic aberration. Glass has better temperature characteristics than plastic, which helps improve the reliability of the lens in high-temperature and high-humidity environments. This application does not specifically limit the number of lenses made of plastic or glass; if temperature performance is a primary concern, all lenses can be made of glass.

[0048] In an exemplary embodiment, the optical imaging lens according to this application uses glass for the spherical lens and plastic for the aspherical lens. This combination of spherical glass and aspherical plastic is beneficial for reducing costs and improving the reliability of the lens in high temperature and high humidity environments.

[0049] In an exemplary embodiment, the effective focal length f of the optical imaging system can be, for example, in the range of 14.5 mm to 15.0 mm; the effective focal length f1 of the first lens can be, for example, in the range of 7.8 mm to 8.2 mm; the effective focal length f2 of the second lens can be, for example, in the range of 30.0 mm to 1844.8 mm; the effective focal length f3 of the third lens can be, for example, in the range of -6.4 mm to -5.0 mm; and the effective focal length f4 of the fourth lens can be, for example, in the range of 13.0 mm to 23.0 mm. Half the image height ImgH corresponding to the maximum field of view of the optical imaging system can be, for example, in the range of 4.0 mm to 5.0 mm; exemplarily, ImgH is 4.03 mm. The distance TD on the optical axis from the object-side surface of the first lens to the image-side surface of the fourth lens can be, for example, in the range of 4.0 mm to 4.5 mm.

[0050] In an exemplary embodiment, the optical imaging system may further include a prism positioned between the fourth lens and the imaging plane. The prism is used to reflect light from the back end of the optical imaging system to the image sensor. This design makes the prism shape invisible, allowing the phone's appearance to remain consistent with conventional lenses, resulting in a more aesthetically pleasing design.

[0051] In an exemplary embodiment, the optical imaging system according to this application further includes a filter for correcting color deviation and / or a protective glass for protecting the photosensitive element located on the imaging surface.

[0052] The optical imaging lens according to the exemplary embodiments of this application has telephoto characteristics. In application, the optical imaging lens according to the exemplary embodiments of this application can employ a periscope lens design, with its length direction set along the vertical or horizontal direction of the electronic device, thereby achieving the purpose of reducing the thickness of the electronic device body. The optical imaging lens according to the above embodiments of this application can employ multiple lens elements, such as the four elements mentioned above. By reasonably arranging the various lenses of the optical imaging lens, the telephoto characteristics of the lens are achieved, thereby realizing good telephoto shooting effects.

[0053] However, those skilled in the art will understand that the number of lenses constituting the optical imaging lens can be varied to obtain the various results and advantages described herein without departing from the technical solutions claimed in this application. For example, although four lenses are described as an example in the embodiments, the optical imaging lens is not limited to including four lenses. If desired, the optical imaging lens may also include other numbers of lenses.

[0054] Specific embodiments of the optical imaging system applicable to the above-described embodiments are further described below with reference to the accompanying drawings.

[0055] Example 1

[0056] The following is for reference Figures 1 to 2D An optical imaging system according to Embodiment 1 of this application is described. Figure 1 A schematic diagram of the structure of an optical imaging system according to Embodiment 1 of this application is shown.

[0057] like Figure 1 As shown, the optical imaging system includes, in sequence from the object side to the image side, an aperture stop STO, a first lens E1, a second lens E2, a third lens E3, a fourth lens E4, a prism E5, a filter E6, and an imaging surface S13.

[0058] The first lens E1 has positive optical power, with its object-side surface S1 being convex and its image-side surface S2 being concave. The second lens E2 has positive optical power, with its object-side surface S3 being convex and its image-side surface S4 being concave. The third lens E3 has negative optical power, with its object-side surface S5 being convex and its image-side surface S6 being concave. The fourth lens E4 has positive optical power, with its object-side surface S7 being convex and its image-side surface S8 being convex. The prism E5 has an object-side surface S9 and an image-side surface S10. The filter E6 has an object-side surface S11 and an image-side surface S12. Light from the object passes sequentially through surfaces S1 to S12 and is finally imaged onto the imaging surface S13.

[0059] Table 1 shows the basic parameters of the optical imaging system of Example 1, where the units for radius of curvature, thickness / distance, and effective focal length are millimeters (mm).

[0060]

[0061] Table 1

[0062] In Example 1, the object-side surface and image-side surface of any one of the second lens E2 to the fourth lens E4 are aspherical, and the surface shape of each aspherical lens is... The following aspherical formulas can be used for limitation:

[0063] (1)

[0064] in, For an aspherical surface along the optical axis at a height of h When the position is such that the distance from the vertex of the non-spherical surface is the sag; c For the paraxial curvature of an aspherical surface, c =1 / R (i.e., paraxial curvature) c (The reciprocal of the radius of curvature R in Table 1 above). k The conic coefficient; Ai Is it an aspherical first i -th order correction coefficients. Tables 2-1 and 2-2 give the higher-order coefficients that can be used for the aspherical mirrors S3-S8 in Example 1. A 4 , A 6 , A 8 , A 10 , A 12 , A 14 , A 16 , A 18 , A 20 , A 22 , A 24 , A 26 , A 28 and A 30 .

[0065]

[0066] Table 2-1

[0067]

[0068] Table 2-2

[0069] In this embodiment, the effective focal length f of the optical imaging system is 14.61 mm, half the image height ImgH corresponding to the maximum field of view of the optical imaging system is 4.03 mm, the distance TD on the optical axis from the object side of the first lens to the image side of the fourth lens is 4.20 mm, the maximum field of view FOV of the optical imaging system is 30.7°, the combined focal length f12 of the first and second lenses is 6.49 mm, the combined focal length f34 of the third and fourth lenses is -9.20 mm, the effective half-aperture DT41 of the object side of the fourth lens is 2.29 mm, the effective half-aperture DT42 of the image side of the fourth lens is 2.27 mm, the effective half-aperture DT12 of the image side of the first lens is 3.05 mm, the edge thickness ET1 of the first lens is 0.76 mm, the edge thickness ET2 of the second lens is 0.40 mm, the edge thickness ET3 of the third lens is 1.17 mm, and the edge thickness ET4 of the fourth lens is 0.26 mm.

[0070] Figure 2A The on-axis chromatic aberration curve of the optical imaging system of Embodiment 1 is shown, which represents the deviation of the focal point of light of different wavelengths after passing through the lens. Figure 2B The astigmatism curves of the optical imaging system of Embodiment 1 are shown, which represent the meridional image plane curvature and the sagittal image plane curvature. Figure 2C The distortion curves of the optical imaging system of Example 1 are shown, which represent the distortion magnitude values ​​corresponding to different image heights. Figure 2D The magnification chromatic aberration curve of the optical imaging system of Embodiment 1 is shown, which represents the deviation of different image heights on the imaging plane after light passes through the lens. According to Figures 2A to 2D It can be seen that the optical imaging system given in Example 1 can achieve good imaging quality.

[0071] Example 2

[0072] The following is for reference Figures 3 to 4D An optical imaging system according to Embodiment 2 of this application is described. In this embodiment and the following embodiments, for the sake of brevity, descriptions similar to those in Embodiment 1 will be omitted. Figure 3 A schematic diagram of the structure of an optical imaging system according to Embodiment 2 of this application is shown.

[0073] like Figure 3 As shown, the optical imaging system includes, in sequence from the object side to the image side, an aperture stop STO, a first lens E1, a second lens E2, a third lens E3, a fourth lens E4, a prism E5, a filter E6, and an imaging surface S13.

[0074] The first lens E1 has positive optical power, with its object-side surface S1 being convex and its image-side surface S2 being concave. The second lens E2 has positive optical power, with its object-side surface S3 being convex and its image-side surface S4 being concave. The third lens E3 has negative optical power, with its object-side surface S5 being convex and its image-side surface S6 being concave. The fourth lens E4 has positive optical power, with its object-side surface S7 being concave and its image-side surface S8 being convex. The prism E5 has an object-side surface S9 and an image-side surface S10. The filter E6 has an object-side surface S11 and an image-side surface S12. Light from the object passes sequentially through surfaces S1 to S12 and is finally imaged on the imaging surface S13.

[0075] Table 3 shows the basic parameters of the optical imaging system of Example 2, where the units for radius of curvature, thickness / distance, and effective focal length are millimeters (mm). Tables 4-1 and 4-2 show the higher-order coefficients that can be used for each aspherical mirror in Example 2, where each aspherical surface shape can be defined by formula (1) given in Example 1 above.

[0076]

[0077] Table 3

[0078]

[0079] Table 4-1

[0080]

[0081] Table 4-2

[0082] In this embodiment, the effective focal length f of the optical imaging system is 14.91 mm, half the image height ImgH corresponding to the maximum field of view of the optical imaging system is 4.03 mm, the distance TD on the optical axis from the object side of the first lens to the image side of the fourth lens is 4.20 mm, the maximum field of view FOV of the optical imaging system is 30.1°, the combined focal length f12 of the first and second lenses is 6.71 mm, the combined focal length f34 of the third and fourth lenses is -9.57 mm, the effective half-aperture DT41 of the object side of the fourth lens is 2.34 mm, the effective half-aperture DT42 of the image side of the fourth lens is 2.39 mm, the effective half-aperture DT12 of the image side of the first lens is 3.14 mm, the edge thickness ET1 of the first lens is 0.59 mm, the edge thickness ET2 of the second lens is 0.37 mm, the edge thickness ET3 of the third lens is 1.08 mm, and the edge thickness ET4 of the fourth lens is 0.34 mm.

[0083] Figure 4A The on-axis chromatic aberration curve of the optical imaging system of Embodiment 2 is shown, which represents the deviation of the focal point of light of different wavelengths after passing through the lens. Figure 4BThe astigmatism curves of the optical imaging system of Embodiment 2 are shown, which represent the meridional image plane curvature and the sagittal image plane curvature. Figure 4C The distortion curves of the optical imaging system of Example 2 are shown, which represent the distortion magnitude values ​​corresponding to different image heights. Figure 4D The magnification chromatic aberration curve of the optical imaging system of Embodiment 2 is shown, which represents the deviation of different image heights on the imaging plane after light passes through the lens. According to Figures 4A to 4D It can be seen that the optical imaging system given in Example 2 can achieve good imaging quality.

[0084] Example 3

[0085] The following is for reference Figures 5 to 6D An optical imaging system according to Embodiment 3 of this application is described. Figure 5 A schematic diagram of the structure of an optical imaging system according to Embodiment 3 of this application is shown.

[0086] like Figure 5 As shown, the optical imaging system includes, from the object side to the image side, a first lens E1, a second lens E2, a third lens E3, a fourth lens E4, a prism E5, a filter E6, and an imaging surface S13.

[0087] The first lens E1 has positive optical power, with its object-side surface S1 being convex and its image-side surface S2 being concave. The second lens E2 has positive optical power, with its object-side surface S3 being convex and its image-side surface S4 being concave. The third lens E3 has negative optical power, with its object-side surface S5 being concave and its image-side surface S6 being concave. The fourth lens E4 has positive optical power, with its object-side surface S7 being concave and its image-side surface S8 being convex. The prism E5 has an object-side surface S9 and an image-side surface S10. The filter E6 has an object-side surface S11 and an image-side surface S12. Light from the object passes sequentially through surfaces S1 to S12 and is finally imaged onto the imaging surface S13.

[0088] Table 5 shows the basic parameters of the optical imaging system of Example 3, where the units for radius of curvature, thickness / distance, and effective focal length are millimeters (mm). Tables 6-1 and 6-2 show the higher-order coefficients that can be used for each aspherical mirror in Example 3, where each aspherical surface shape can be defined by formula (1) given in Example 1 above.

[0089]

[0090] Table 5

[0091]

[0092] Table 6-1

[0093]

[0094] Table 6-2

[0095] In this embodiment, the effective focal length f of the optical imaging system is 14.81 mm, half the image height ImgH corresponding to the maximum field of view of the optical imaging system is 4.03 mm, the distance TD on the optical axis from the object side of the first lens to the image side of the fourth lens is 4.22 mm, the maximum field of view FOV of the optical imaging system is 30.4°, the combined focal length f12 of the first and second lenses is 7.52 mm, the combined focal length f34 of the third and fourth lenses is -12.21 mm, the effective half-aperture DT41 of the object side of the fourth lens is 2.29 mm, the effective half-aperture DT42 of the image side of the fourth lens is 2.28 mm, the effective half-aperture DT12 of the image side of the first lens is 3.15 mm, the edge thickness ET1 of the first lens is 0.50 mm, the edge thickness ET2 of the second lens is 0.69 mm, the edge thickness ET3 of the third lens is 0.85 mm, and the edge thickness ET4 of the fourth lens is 0.31 mm.

[0096] Figure 6A The on-axis chromatic aberration curve of the optical imaging system of Embodiment 3 is shown, which represents the deviation of the focal point of light of different wavelengths after passing through the lens. Figure 6B The astigmatism curves of the optical imaging system of Example 3 are shown, which represent the meridional image plane curvature and the sagittal image plane curvature. Figure 6C The distortion curves of the optical imaging system of Example 3 are shown, which represent the distortion magnitude values ​​corresponding to different image heights. Figure 6D The magnification chromatic aberration curve of the optical imaging system of Embodiment 3 is shown, which represents the deviation of different image heights on the imaging plane after light passes through the lens. According to Figures 6A to 6D It can be seen that the optical imaging system given in Example 3 can achieve good imaging quality.

[0097] Example 4

[0098] The following is for reference Figures 7 to 8D An optical imaging system according to Embodiment 4 of this application is described. Figure 7 A schematic diagram of the structure of an optical imaging system according to Embodiment 4 of this application is shown.

[0099] like Figure 7 As shown, the optical imaging system includes, in sequence from the object side to the image side, an aperture stop STO, a first lens E1, a second lens E2, a third lens E3, a fourth lens E4, a prism E5, a filter E6, and an imaging surface S13.

[0100] The first lens E1 has positive optical power, with its object-side surface S1 being convex and its image-side surface S2 being concave. The second lens E2 has positive optical power, with its object-side surface S3 being convex and its image-side surface S4 being concave. The third lens E3 has negative optical power, with its object-side surface S5 being concave and its image-side surface S6 being concave. The fourth lens E4 has positive optical power, with its object-side surface S7 being convex and its image-side surface S8 being convex. The prism E5 has an object-side surface S9 and an image-side surface S10. The filter E6 has an object-side surface S11 and an image-side surface S12. Light from the object passes sequentially through surfaces S1 to S12 and is finally imaged on the imaging surface S13.

[0101] Table 7 shows the basic parameters of the optical imaging system of Example 4, where the units for radius of curvature, thickness / distance, and effective focal length are millimeters (mm). Tables 8-1 and 8-2 show the higher-order coefficients that can be used for each aspherical mirror in Example 4, where each aspherical surface shape can be defined by formula (1) given in Example 1 above.

[0102]

[0103] Table 7

[0104]

[0105] Table 8-1

[0106]

[0107] Table 8-2

[0108] In this embodiment, the effective focal length f of the optical imaging system is 14.90 mm, half the image height ImgH corresponding to the maximum field of view of the optical imaging system is 4.03 mm, the distance TD on the optical axis from the object side of the first lens to the image side of the fourth lens is 4.19 mm, the maximum field of view FOV of the optical imaging system is 30.2°, the combined focal length f12 of the first and second lenses is 7.45 mm, the combined focal length f34 of the third and fourth lenses is -11.51 mm, the effective half-aperture DT41 of the object side of the fourth lens is 2.26 mm, the effective half-aperture DT42 of the image side of the fourth lens is 2.25 mm, the effective half-aperture DT12 of the image side of the first lens is 3.12 mm, the edge thickness ET1 of the first lens is 0.50 mm, the edge thickness ET2 of the second lens is 0.75 mm, the edge thickness ET3 of the third lens is 0.91 mm, and the edge thickness ET4 of the fourth lens is 0.35 mm.

[0109] Figure 8A The on-axis chromatic aberration curve of the optical imaging system of Embodiment 4 is shown, which represents the deviation of the focal point of light of different wavelengths after passing through the lens. Figure 8B The astigmatism curves of the optical imaging system of Example 4 are shown, which represent the meridional image plane curvature and the sagittal image plane curvature. Figure 8C The distortion curves of the optical imaging system of Example 4 are shown, which represent the distortion magnitude values ​​corresponding to different image heights. Figure 8D The magnification chromatic aberration curve of the optical imaging system of Embodiment 4 is shown, which represents the deviation of different image heights on the imaging plane after light passes through the lens. According to Figures 8A to 8D It can be seen that the optical imaging system given in Example 4 can achieve good imaging quality.

[0110] In summary, Examples 1 to 4 satisfy the relationships shown in Table 9.

[0111]

[0112] Table 9

[0113] 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 optical imaging system described above.

[0114] 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. An optical imaging system, characterized in that, Along the optical axis from the object side to the image side, it includes, in sequence: a first lens, a second lens, a third lens, and a fourth lens; wherein, The first lens has positive optical power, and its object side is convex and its image side is concave. The second lens has positive optical power, with its object side being convex and its image side being concave. The third lens has negative optical power and its image-side surface is concave. The fourth lens has positive optical power and its image-side surface is convex. The optical imaging system has four lenses with optical power. The first lens is made of glass with a refractive index greater than 1.85, and both the object-side and image-side surfaces are spherical; and The effective focal length f of the optical imaging system and the maximum field of view (FOV) of the optical imaging system satisfy the following: 24.60mm≤f / tan(FOV)≤25.75mm; The radius of curvature R1 of the object side surface of the first lens, the radius of curvature R3 of the object side surface of the second lens, the refractive index N1 of the first lens and the refractive index N2 of the second lens satisfy: 3.70mm≤(R1+R3) / (N1+N2)≤4.30mm; The effective focal length f1 of the first lens and the effective focal length f of the optical imaging system satisfy: 3.21≤(f+f1) / (f-f1)≤3.

53.

2. The optical imaging system according to claim 1, characterized in that, The effective focal length f3 of the third lens and the effective focal length f4 of the fourth lens satisfy the following condition: 1.77≤(f4-f3) / (f4+f3)≤2.

55.

3. The optical imaging system according to claim 1, characterized in that, The radius of curvature R1 of the object side of the first lens, the radius of curvature R6 of the image side of the third lens, the refractive index N1 of the first lens and the refractive index N3 of the third lens satisfy: 2.70mm≤(R1+R6) / (N1+N3)<3.3mm.

4. The optical imaging system according to claim 1, characterized in that, The radius of curvature R4 of the image side surface of the second lens, the radius of curvature R8 of the image side surface of the fourth lens, and the effective focal length f of the optical imaging system satisfy: 0.96≤(R4-R8) / f≤1.

59.

5. The optical imaging system according to claim 1, characterized in that, The effective focal length f of the optical imaging system and the distance TD from the object side of the first lens to the image side of the fourth lens on the optical axis satisfy: 3.48≤f / TD≤3.

55.

6. The optical imaging system according to claim 1, characterized in that, The combined focal length f12 of the first lens and the second lens, the center thickness CT1 of the first lens on the optical axis and the center thickness CT2 of the second lens on the optical axis satisfy: 3.08≤f12 / (CT1+CT2)<3.

8.

7. The optical imaging system according to any one of claims 1 to 6, characterized in that, The effective half-aperture DT41 of the object side of the fourth lens, the effective half-aperture DT42 of the image side of the fourth lens and the effective half-aperture DT12 of the image side of the first lens satisfy: 1.44≤(DT41+DT42) / DT12≤1.

51.

8. The optical imaging system according to any one of claims 1 to 6, characterized in that, The combined focal length f34 of the third lens and the fourth lens, the edge thickness ET3 of the third lens and the edge thickness ET4 of the fourth lens satisfy: -10.54≤f34 / (ET3+ET4)≤-6.

42.

9. The optical imaging system according to any one of claims 1 to 6, characterized in that, The edge thickness ET1 of the first lens, the edge thickness ET2 of the second lens, and the air gap T23 between the second lens and the third lens on the optical axis satisfy: 1.60≤(ET1+ET2) / T23<2.

9.

10. The optical imaging system according to any one of claims 1 to 6, characterized in that, The edge thickness ET3 of the third lens, the center thickness CT3 of the third lens on the optical axis, and the air gap T34 between the third lens and the fourth lens on the optical axis satisfy the following condition: 0.84≤ET3 / (CT3+T34)≤1.14.

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