A distortion-free optical imaging system

Abstract

The present invention discloses an aberration-free optical imaging system, which includes four aspherical lenses. From the object plane to the image plane, they are in sequence: a stop (STO), a first lens (P1), a second lens (P2), a third lens (P3), and a fourth lens (P4). The first lens (P1) is a positive lens; the second lens (P2) is a negative lens; the third lens (P3) is a positive lens; the fourth lens (P4) is a negative lens. The aberration-free optical imaging system satisfies the relational expressions: 1.0 < f1 / f < 1.5; -1.6 < f2 / f < -1.3; 0.4 < f3 / f < 0.9; -1.0 < f4 / f < -0.7. The combination of positive and negative lenses is beneficial to reducing the tolerance sensitivity of the system, reducing aberration, and achieving a good imaging effect.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical imaging systems, and more specifically, relates to a small optical imaging system applied to electronic products. Background Art

[0002] In recent years, people's requirements for electronic products have become increasingly miniaturized and portable, which has led to the booming development of miniaturized camera lenses. Most of the existing miniaturized camera lenses make concessions in distortion in order to balance miniaturization and a large field of view. There is a large distortion, and there are large visible deformations at the corners of the imaging画面, which has a great impact on subsequent image processing and image display. Therefore, there is an urgent need for an optical imaging system with miniaturization, a large field of view, and small distortion. Summary of the Invention

[0003] The present invention provides an aberration-free optical imaging system, which includes four aspherical lenses. From the object plane to the image plane, they are successively the stop (STO), the first lens (P1), the second lens (P2), the third lens (P3), and the fourth lens (P4); the first lens (P1) is a positive lens, its object side is convex, and its image side is convex; the second lens (P2) is a negative lens, its object side is concave, and its image side is concave; the third lens (P3) is a positive lens, its object side is concave, and its image side is convex; the fourth lens (P4) is a negative lens, its object side is convex, and its image side is concave; the aberration-free optical imaging system satisfies the following relational expressions: 1.0 < f1 / f < 1.5; -1.6 < f2 / f < -1.3; 0.4 < f3 / f < 0.9; -1.0 < f4 / f < -0.7; where f1 is the effective focal length of the first lens element (P1), f2 is the effective focal length of the second lens element (P2), f3 is the effective focal length of the third lens element (P3), f4 is the effective focal length of the fourth lens element (P4), and f is the effective focal length of the aberration-free optical imaging system.

[0004] Preferably, the first lens (P1), the second lens (P2), the third lens (P3), and the fourth lens (P4) are all made of plastic and satisfy the following relational expressions: 1 < CT1 / ET1 < 2; 0.5 < CT2 / ET2 < 1; 1 < CT3 / ET3 < 3; 0.5 < CT4 / ET4 < 1; where CT1 is the thickness of the first lens (P1) on the optical axis, ET1 is the thickness of the first lens (P1) at the maximum aperture; CT2 is the thickness of the second lens (P2) on the optical axis, ET2 is the thickness of the second lens (P2) at the maximum aperture; CT3 is the thickness of the third lens (P3) on the optical axis, ET3 is the thickness of the third lens (P3) at the maximum aperture; CT4 is the thickness of the fourth lens (P4) on the optical axis, ET4 is the thickness of the fourth lens (P4) at the maximum aperture.

[0005] Preferably, it also satisfies the following relational expression: F < 2.5; where F is the image-side F-number.

[0006] Preferably, the aperture stop (STO) is located in front of the first lens (P1) and satisfies the following relational expression: 1 < (T12 + T34) / T23 < 3.5; where T12 is the air separation distance between the first lens (P1) and the second lens (P2) on the optical axis, T23 is the air separation distance between the second lens (P2) and the third lens (P3) on the optical axis, and T34 is the air separation distance between the third lens (P3) and the fourth lens (P4) on the optical axis.

[0007] Preferably, it also satisfies the following relational expressions: 0.05 < H1 < 0.09; 0.3 < H2 < 0.5; where H1 is the distance from the center of the aspherical surface (S1) on the object side of the first lens (P1) to the maximum effective diameter in the direction parallel to the optical axis, and H2 is the distance from the center of the aspherical surface (S2) on the image side of the first lens (P1) to the maximum effective diameter in the direction parallel to the optical axis.

[0008] Preferably, it also satisfies the following relational expressions: 0.20 < CT1 / ∑T < 0.31; 0.15 < CT2 / ∑T < 0.25; 0.30 < CT3 / ∑T < 0.45; 0.15 < CT4 / ∑T < 0.25; where ∑T is the sum of the lens thicknesses of the first lens (P1), the second lens (P2), the third lens (P3), and the fourth lens (P4) on the optical axis, and CT1, CT2, CT3, and CT4 are the lens thicknesses of the first lens (P1), the second lens (P2), the third lens (P3), and the fourth lens (P4) on the optical axis, respectively.

[0009] Compared with the prior art, the present invention has the following advantages:

[0010] (1) The present invention has a small F-number, a large aperture, and sufficient light intake; (2) While ensuring small distortion, the present invention also has a high relative illuminance in the edge field of view, ensuring the brightness uniformity of the overall picture; (3) The center thickness of each lens in the present invention is moderate, and the air gap is small, which is conducive to reducing the total length of the optical system and achieving miniaturization; (4) By combining positive and negative lenses with each other and balancing the optical power of each lens, the present invention is conducive to reducing astigmatism and distortion and improving the imaging quality. Description of the Drawings

[0011] Figure 1 It is a schematic structural diagram of a distortion-free optical imaging system.

[0012] Figure 2 It is a distortion diagram of a distortion-free optical imaging system.

[0013] Figure 3 It is an astigmatism curve diagram of a distortion-free optical imaging system. Detailed Embodiments

[0014] In order to make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0015] A distortion-free optical imaging system, characterized in that the distortion-free optical imaging system includes four aspherical lenses, which are, in sequence from the object plane to the image plane, a stop (STO), a first lens (P1), a second lens (P2), a third lens (P3), and a fourth lens (P4); the first lens (P1) is a positive lens, its object side is convex, and its image side is convex; the second lens (P2) is a negative lens, its object side is concave, and its image side is concave; the third lens (P3) is a positive lens, its object side is concave, and its image side is convex; the fourth lens (P4) is a negative lens, its object side is convex, and its image side is concave; the distortion-free optical imaging system satisfies the following relational expressions: 1.0 < f1 / f < 1.5; -1.6 < f2 / f < -1.3; 0.4 < f3 / f < 0.9; -1.0 < f4 / f < -0.7; where f1 is the effective focal length of the first lens element (P1), f2 is the effective focal length of the second lens element (P2), f3 is the effective focal length of the third lens element (P3), f4 is the effective focal length of the fourth lens element (P4), and f is the effective focal length of the distortion-free optical imaging system. The positive and negative lenses of the first lens (P1), the second lens (P2), the third lens (P3), and the fourth lens (P4) are alternately combined with each other, which can effectively correct aberrations and improve image quality; the ratios of the effective focal lengths of each lens to the effective focal length of the system are relatively close, balancing the optical power of each lens and reducing the tolerance sensitivity of the system.

[0016] As for the distortion-free optical imaging system as described above, preferably, the materials of the first lens (P1), the second lens (P2), the third lens (P3), and the fourth lens (P4) are all plastic and satisfy the following relationship: 1<CT1 / ET1<2; 0.5<CT2 / ET2<1; 1<CT3 / ET3<3; 0.5<CT4 / ET4<1; wherein CT1 is the thickness of the first lens (P1) on the optical axis, and ET1 is the thickness of the first lens (P1) at the maximum aperture; CT2 is the thickness of the second lens (P2) on the optical axis, and ET2 is the thickness of the second lens (P2) at the maximum aperture; CT3 is the thickness of the third lens (P3) on the optical axis, and ET3 is the thickness of the third lens (P3) at the maximum aperture; CT4 is the thickness of the fourth lens (P4) on the optical axis, and ET4 is the thickness of the fourth lens (P4) at the maximum aperture. All four lenses are made of plastic, which reduces production costs. At the same time, the ratio of the center thickness to the edge thickness of each lens is moderate, which is convenient for injection molding.

[0017] The above-mentioned distortion-free optical imaging system preferably satisfies the following relationship: F<2.5; where F is the image-side F number. The smaller the image-side F number is and the larger the aperture is, the more light the system receives, and the better the overall illumination will be.

[0018] In the above-mentioned distortion-free optical imaging system, preferably, the aperture (STO) is located before the first lens (P1) and satisfies the following relationship: 1<(T12+T34) / T23<3.5; wherein T12 is the air spacing distance between the first lens (P1) and the second lens (P2) on the optical axis, T23 is the air spacing distance between the second lens (P2) and the third lens (P3) on the optical axis, and T34 is the air spacing distance between the third lens (P3) and the fourth lens (P4) on the optical axis. The aperture is located before the first lens and the air spacing of the optical system is small and reasonably distributed, which is conducive to reducing the overall length of the system and achieving miniaturization.

[0019] The above-mentioned distortion-free optical imaging system preferably satisfies the following relationship: 0.05

[0020] ​The aberration-free optical imaging system described above preferably satisfies the following relationships: 0.20 < CT1 / ∑T < 0.31; 0.15 < CT2 / ∑T < 0.25; 0.30 < CT3 / ∑T < 0.45; 0.15 < CT4 / ∑T < 0.25; where ∑T is the sum of the lens thicknesses of the first lens (P1), the second lens (P2), the third lens (P3), and the fourth lens (P4) on the optical axis, and CT1, CT2, CT3, and CT4 are the lens thicknesses of the first lens (P1), the second lens (P2), the third lens (P3), and the fourth lens (P4) on the optical axis, respectively. Controlling the thickness of each lens is beneficial for correcting aberrations and compensating for each other, can reduce the tolerance sensitivity and the molding difficulty. At the same time, it is beneficial to reduce the overall length of the lens and achieve the ultra-thinning and miniaturization of the lens.

[0021] Embodiment 1

[0022] As a specific embodiment of the present invention, the parameters of the aberration-free optical imaging system are shown in Table 1 below.

[0023] Table 1 Structural parameter table of the aberration-free optical imaging system.

[0024]

[0025] Table 2 Ratio sag / r of the sag of each lens surface to the radius r of the aberration-free optical imaging system.

[0026]

[0027] For the convenience of those skilled in the art to understand, the above is only the preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A distortion-free optical imaging system, characterized in that: The distortion-free optical imaging system comprises four aspheric lenses, which are, from the object plane to the image plane, an aperture stop (STO), a first lens (P1), a second lens (P2), a third lens (P3), and a fourth lens (P4); The first lens (P1) is a positive lens, the object side surface of which is convex, and the image side surface of which is convex; The second lens (P2) is a negative lens, the object side surface of which is concave, and the image side surface of which is concave; The third lens (P3) is a positive lens, the object side surface of which is concave and the image side surface of which is convex; The fourth lens (P4) is a negative lens, the object side surface of which is convex and the image side surface is concave; The distortion-free optical imaging system satisfies the following relationship: 1.0 <f1 / f<1.5; -1.6 <f2 / f<-1.3; 0.4 <f3 / f<0.9; -1.0 <f4 / f<-0.7; Wherein, f1 is the effective focal length of the first lens (P1), f2 is the effective focal length of the second lens (P2), f3 is the effective focal length of the third lens (P3), f4 is the effective focal length of the fourth lens (P4), and f is the effective focal length of the distortion-free optical imaging system; The materials of the first lens (P1), the second lens (P2), the third lens (P3), and the fourth lens (P4) are all plastic and satisfy the following relationship: 1<CT1 / ET1<2; 0.5<CT2 / ET2<1; 1<CT3 / ET3<3; 0.5<CT4 / ET4<1; Wherein, CT1 is the thickness of the first lens (P1) on the optical axis, and ET1 is the thickness of the first lens (P1) at the maximum aperture; CT2 is the thickness of the second lens (P2) on the optical axis, and ET2 is the thickness of the second lens (P2) at the maximum aperture; CT3 is the thickness of the third lens (P3) on the optical axis, and ET3 is the thickness of the third lens (P3) at the maximum aperture; CT4 is the thickness of the fourth lens (P4) on the optical axis, and ET4 is the thickness of the fourth lens (P4) at the maximum aperture; The distortion-free optical imaging system satisfies the following relationship: F<2.5； Where, F is the image-side F number; In the distortion-free optical imaging system, the stop (STO) is located before the first lens (P1) and satisfies the following relationship: 1<(T12+T34) / T23<3.5; Wherein, T12 is the air distance between the first lens (P1) and the second lens (P2) on the optical axis, T23 is the air distance between the second lens (P2) and the third lens (P3) on the optical axis, and T34 is the air distance between the third lens (P3) and the fourth lens (P4) on the optical axis; The distortion-free optical imaging system satisfies the following relationship: 0.05mm <H1<0.09mm; 0.3mm <H2<0.5mm; Wherein, H1 is the distance from the center of the object-side aspheric surface (S1) of the first lens (P1) to the maximum effective diameter in the direction parallel to the optical axis; H2 is the distance from the center of the image-side aspheric surface (S2) of the first lens (P1) to the maximum effective diameter in the direction parallel to the optical axis; The distortion-free optical imaging system satisfies the following relationship: 0.20 <CT1 / ∑T<0.31; 0.15 <CT2 / ∑T<0.25; 0.30 <CT3 / ∑T<0.45; 0.15 <CT4 / ∑T<0.25; Wherein, ∑T is the sum of the lens thicknesses of the first lens (P1), the second lens (P2), the third lens (P3), and the fourth lens (P4) on the optical axis, and CT1, CT2, CT3, and CT4 are the lens thicknesses of the first lens (P1), the second lens (P2), the third lens (P3), and the fourth lens (P4) on the optical axis, respectively.

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