Ultra-wide-angle near-infrared imaging system

Abstract

The invention discloses an ultra-wide-angle near-infrared imaging system. A first lens (G1), a second lens (L2), a third lens (G3), a diaphragm (STO), a fourth lens (L4), a fifth lens (L5), a sixth lens (L6) and an optical filter (IR) are sequentially arranged from an object plane to an image plane; the effective surface calibers of the first lens and the second lens are large, so that the field angle is large, and the F number is small; the lens type adopts a spherical surface and an aspheric surface, and the negative lens and the positive lens are combined with each other, so that aberration reduction and f theta distortion control are facilitated, the imaging effect is good, and the MTF at the cut-off frequency is high; the second, fourth, fifth and sixth lenses are made of plastic materials, so that the cost is controlled.

Description

[Technical field]

[0001] The invention relates to an optical lens imaging system, in particular to an ultra-wide-angle near-infrared imaging system. [Background technology]

[0002] As virtual reality technology matures, more and more AR products are being used by everyone. For user experience, the field of view and image quality of AR products will greatly affect the user experience. Many AR products cannot achieve a large field of view, resulting in a small image range. If the field of view is large, it will lead to large distortion, poor imaging quality and other problems. The present invention is an ultra-wide-angle near-infrared imaging system designed under this background. [Summary of the invention]

[0003] In response to the needs of the existing market and research on room for improvement, the present invention provides an ultra-wide-angle near-infrared imaging system, which aims to solve the technical problem that the optics of the current ultra-wide-angle near-infrared imaging system cannot ensure a large field of view while ensuring small distortion and high imaging quality.

[0004] To achieve the above object, the present invention provides an ultra-wide-angle near-infrared imaging system, comprising a first lens (G1), a second lens (L2), a third lens (G3), a stop (STO), a fourth lens (L4), a fifth lens (L5), a sixth lens (L6), and a filter (IR) arranged in sequence from the object plane to the image plane;

[0005] The first lens (G1) is a negative lens, made of glass, with a focal length satisfying -6.0<f1 / f<-5.0; the object side surface is convex and spherical, and the image side surface is concave and spherical;

[0006] The second lens (L2) is a negative lens, made of plastic, with a focal length satisfying -2.0<f2 / f<-1.0; the object side surface is convex and aspherical, and the image side surface is concave and aspherical;

[0007] The third lens (G3) is a positive lens, made of glass, with a focal length satisfying 1.5<f3 / f<2.0; the object side surface is convex and spherical, and the image side surface is convex and spherical;

[0008] The fourth lens (L4) is a negative lens, made of plastic, with a focal length satisfying -10.0<f4 / f<-9.0; the object side surface is convex and aspherical, and the image side surface is concave and aspherical;

[0009] The fifth lens (L5) is a positive lens, made of plastic, with a focal length satisfying 5.0<f5 / f<6.0; the object side surface is a concave and aspherical surface, and the image side surface is a convex and aspherical surface;

[0010] The sixth lens (L6) is a positive lens, made of plastic, with a focal length satisfying 2.0<f6 / f<3.0; the object side surface is convex and aspherical, and the image side surface is concave and aspherical;

[0011] The ultra-wide-angle near-infrared imaging system satisfies the following relationship:

[0012] 18.0<TTL / f<20.0;

[0013] TTL<11mm;

[0014] 4.0<F / f<4.5;

[0015] Among them, f1 is the effective focal length of the first lens, f2 is the effective focal length of the second lens, f3 is the effective focal length of the third lens, f4 is the effective focal length of the fourth lens, f5 is the effective focal length of the fifth lens, f6 is the effective focal length of the sixth lens, TTL is the axial distance from the object side of the first lens to the imaging surface; f is the effective focal length of the ultra-wide-angle near-infrared imaging system, and F is the F number of the ultra-wide-angle near-infrared imaging system.

[0016] Preferably, the ultra-wide-angle near-infrared imaging system satisfies the following relationship:

[0017] 23<Y1 / f<25;

[0018] 8<Y2 / f<10;

[0019] 230°<FOV<235°;

[0020] Wherein, Y1 is the effective aperture of the object side (S1) of the first lens (G1), Y2 is the effective aperture of the object side (S3) of the second lens (L2), f is the effective focal length of the ultra-wide-angle near-infrared imaging system, and FOV is the maximum field of view of this ultra-wide-angle near-infrared imaging system.

[0021] Preferably, the ultra-wide-angle near-infrared imaging system satisfies the following relationship:

[0022] 3.0<T12 / f<3.5;

[0023] 3.5<T23 / f<4.0;

[0024] 1.5<T34 / f<2.0;

[0025] 0.08<T45 / f<0.1;

[0026] 0.01<T56 / f<0.02;

[0027] 0.30<T1 / ∑T<0.35;

[0028] 0.10<T2 / ∑T<0.15;

[0029] 0.25<T3 / ∑T<0.30;

[0030] 0.05<T4 / ∑T<0.10;

[0031] 0.10<T5 / ∑T<0.15;

[0032] 0.10<T6 / ∑T<0.15;

[0033] Among them, T12 is the air distance between the first lens and the second lens on the optical axis, T23 is the air distance between the second lens and the third lens on the optical axis, T34 is the air distance between the third lens and the fourth lens on the optical axis, T45 is the air distance between the fourth lens and the fifth lens on the optical axis, T56 is the air distance between the fifth lens and the sixth lens on the optical axis, and f is the effective focal length of the ultra-wide-angle near-infrared imaging system. ∑T is the sum of the lens thicknesses of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens on the optical axis, respectively, and T1, T2, T3, T4, T5, and T6 are the lens thicknesses of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens on the optical axis, respectively.

[0034] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0035] 1. In the ultra-wide-angle near-infrared imaging system, the effective surface apertures of the first lens (G1) and the second lens (L2) are both relatively large, which is conducive to increasing the field of view angle; the effective focal length of the fourth lens is large, which is conducive to reducing aberrations; while the F number is small, the air intervals between the fourth lens, the fifth lens and the sixth lens are small, and a good depth of field is achieved.

[0036] 2. In the ultra-wide-angle near-infrared imaging system, the aperture is located between the image side surface of the third lens and the object side surface of the fourth lens, the second lens and the third lens, the fourth lens and the fifth lens are a combination of a negative lens and a positive lens, and the second lens, the fourth lens, the fifth lens and the sixth lens are aspherical lenses, which is beneficial to control distortion and improve imaging quality, and the MTF is greater than 45% at the limit frequency.

Brief Description of the Drawings

[0037] Figure 1 This is a schematic diagram of the structure of the ultra-wide-angle near-infrared imaging system.

[0038] Figure 2 This is the MTF diagram of the ultra-wide-angle near-infrared imaging system. [Specific implementation method]

[0039] In order to explain the purpose and technical solution of the present invention in detail, it will be described in conjunction with the embodiments, and the accompanying drawings are all data of this embodiment. It can be said that the embodiment data disclosed in the present invention is complete, but it is not limited to this embodiment. The technical features involved can be explained and illustrated in this embodiment.

[0040] The ultra-wide-angle near-infrared imaging system proposed by the present invention comprises a first lens (G1), a second lens (L2), a third lens (G3), an aperture (STO), a fourth lens (L4), a fifth lens (L5), a sixth lens (L6), and a filter (IR) which are arranged in sequence from the object plane to the image plane;

[0041] The first lens (G1) is a negative lens, made of glass, with a focal length satisfying -6.0<f1 / f<-5.0; the object side surface is convex and spherical, and the image side surface is concave and spherical;

[0042] The second lens (L2) is a negative lens, made of plastic, with a focal length satisfying -2.0<f2 / f<-1.0; the object side surface is convex and aspherical, and the image side surface is concave and aspherical;

[0043] The third lens (G3) is a positive lens, made of glass, with a focal length satisfying 1.5<f3 / f<2.0; the object side surface is convex and spherical, and the image side surface is convex and spherical;

[0044] The fourth lens (L4) is a negative lens, made of plastic, with a focal length satisfying -10.0<f4 / f<-9.0; the object side surface is convex and aspherical, and the image side surface is concave and aspherical;

[0045] The fifth lens (L5) is a positive lens, made of plastic, with a focal length satisfying 5.0<f5 / f<6.0; the object side surface is a concave and aspherical surface, and the image side surface is a convex and aspherical surface;

[0046] The sixth lens (L6) is a positive lens, made of plastic, with a focal length satisfying 2.0<f6 / f<3.0; the object side surface is convex and aspherical, and the image side surface is concave and aspherical;

[0047] The ultra-wide-angle near-infrared imaging system satisfies the following relationship:

[0048] 18.0<TTL / f<20.0;

[0049] TTL<11mm;

[0050] 4.0<F / f<4.5;

[0051] Among them, f1 is the effective focal length of the first lens, f2 is the effective focal length of the second lens, f3 is the effective focal length of the third lens, f4 is the effective focal length of the fourth lens, f5 is the effective focal length of the fifth lens, f6 is the effective focal length of the sixth lens, TTL is the on-axis distance from the object side of the first lens to the imaging surface; f is the effective focal length of the ultra-wide-angle near-infrared imaging system, and F is the F number of the ultra-wide-angle near-infrared imaging system. In this optical system, the second lens and the third lens, the fourth lens and the fifth lens are combined with negative lenses and positive lenses, and the second lens, the fourth lens, the fifth lens and the sixth lens are aspherical lenses. At the same time, the focal length of the fourth lens is large, which is conducive to controlling aberrations, and the focal lengths of other lenses are small, which is conducive to controlling fθ distortion. Wide-angle lenses will inevitably produce distortion. When the angle is greater than a certain degree, fθ distortion evaluation is used, which is essentially the relationship between the actual image height and the ideal image height. The fθ distortion of the present invention is less than 5%, which helps to improve the imaging quality. And the total length TTL is less than 11mm, which is conducive to reducing the size of the optical system. The IR filter used satisfies the transmission of near-infrared light and filters out light of other bands. The smaller the F number of the optical system, the larger the aperture. The F / f of this optical system is not greater than 4.5 and is greater than 4. The depth of field is suitable to meet the imaging requirements. Four of the lenses are made of plastic material, which saves cost and is easy to manufacture.

[0052] Preferably, the ultra-wide-angle near-infrared imaging system is characterized in that it satisfies the following relationship:

[0053] 23<Y1 / f<25;

[0054] 8<Y2 / f<10;

[0055] 230°<FOV<235°;

[0056] Among them, Y1 is the effective aperture of the object side (S1) of the first lens (G1), Y2 is the effective aperture of the object side (S3) of the second lens (L2), f is the effective focal length of the ultra-wide-angle near-infrared imaging system, and FOV is the maximum field of view of this ultra-wide-angle near-infrared imaging system. The effective surface apertures of the first lens (G1) and the second lens (L2) are both large, and the ratio to the effective focal length of the system is greater than 8. The large aperture and symmetrical design are conducive to achieving a large field of view.

[0057] Preferably, the ultra-wide-angle near-infrared imaging system is characterized by satisfying the following relationship:

[0058] 3.0<T12 / f<3.5;

[0059] 3.5<T23 / f<4.0;

[0060] 1.5<T34 / f<2.0;

[0061] 0.08<T45 / f<0.1;

[0062] 0.01<T56 / f<0.02;

[0063] 0.30<T1 / ∑T<0.35;

[0064] 0.10<T2 / ∑T<0.15;

[0065] 0.25<T3 / ∑T<0.30;

[0066] 0.05<T4 / ∑T<0.10;

[0067] 0.10<T5 / ∑T<0.15;

[0068] 0.10<T6 / ∑T<0.15;

[0069] Among them, T12 is the air spacing between the first lens and the second lens on the optical axis, T23 is the air spacing between the second lens and the third lens on the optical axis, T34 is the air spacing between the third lens and the fourth lens on the optical axis, T45 is the air spacing between the fourth lens and the fifth lens on the optical axis, T56 is the air spacing between the fifth lens and the sixth lens on the optical axis, and f is the effective focal length of the ultra-wide-angle near-infrared imaging system. ∑T is the sum of the lens thicknesses of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens on the optical axis, respectively. T1, T2, T3, T4, T5, and T6 are the lens thicknesses of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens on the optical axis, respectively. The air spacing between the fourth lens, the fifth lens, and the sixth lens is small, and the lens thickness is small, so that the optical system is small in size, which helps to achieve miniaturization. The maximum thickness ratio of each lens is also less than 0.35, which is conducive to reducing aberrations and meeting depth of field requirements, and is conducive to clear imaging. The MTF of the imaging system is greater than 45% at the cutoff frequency.

[0070] The following table is the lens data table of the embodiment

[0071] Table 1 Lens data of ultra-wide-angle near-infrared imaging system

[0072] Surface number Surface type Curvature radius / (mm) Thickness / (mm) Material (refractive index: Abbe number) Physical surface Spherical unlimited 317.2275 S1 Spherical 10.2997 1.4185 1.73：44.9 S2 Spherical 2.8585 1.8286 S3 Aspheric 5.1332 0.5401 1.52：55.7 S4 Aspheric 0.7151 1.8901 S5 Spherical 2.7071 1.3226 1.73：27.5 S6 Spherical -2.5150 0.2980 Aperture Spherical unlimited 0.3662 S8 Aspheric 2.6859 0.2501 1.62：22.4 S9 Aspheric 1.8062 0.1911 S10 Aspheric -5.1121 0.3738 1.57：29.9 S11 Aspheric -1.9777 0.0100 S12 Aspheric 1.6540 0.6701 1.52：55.7 S13 Aspheric -7.5220 0.1100 S14 Spherical unlimited 0.6100 1.52：64.2 S15 Spherical unlimited 0.3300 Image plane Spherical unlimited -0.0003

[0073] Table 2 Aspheric lens surface coefficients of ultra-wide-angle near-infrared imaging system

[0074]

[0075]

[0076] The description in this specification only represents the preferred method of the embodiment and does not limit the inventive concept and design technology. As long as it does not go beyond the inventive concept and design technology, it should fall within the protection scope of the present invention.

Claims

1. An ultra-wide-angle near-infrared imaging system, characterized by: A first lens (G1), a second lens (L2), a third lens (G3), an aperture (STO), a fourth lens (L4), a fifth lens (L5), a sixth lens (L6), and an optical filter (IR) are sequentially arranged from the object plane to the image plane; The first lens (G1) is a negative lens, made of glass, with a focal length satisfying -6.0<f1 / f<-5.0; the object side surface is convex and spherical, and the image side surface is concave and spherical; The second lens (L2) is a negative lens, made of plastic, with a focal length satisfying -2.0<f2 / f<-1.0; the object side surface is convex and aspherical, and the image side surface is concave and aspherical; The third lens (G3) is a positive lens, made of glass, with a focal length satisfying 1.5<f3 / f<2.0; the object side surface is convex and spherical, and the image side surface is convex and spherical; The fourth lens (L4) is a negative lens, made of plastic, with a focal length satisfying -10.0<f4 / f<-9.0; the object side surface is convex and aspherical, and the image side surface is concave and aspherical; The fifth lens (L5) is a positive lens, made of plastic, with a focal length satisfying 5.0<f5 / f<6.0; the object side surface is a concave and aspherical surface, and the image side surface is a convex and aspherical surface; The sixth lens (L6) is a positive lens, made of plastic, with a focal length satisfying 2.0<f6 / f<3.0; the object side surface is convex and aspherical, and the image side surface is concave and aspherical; The ultra-wide-angle near-infrared imaging system satisfies the following relationship: 18.0<TTL / f<20.0; TTL<11mm; 4.0<F / f<4.5; Among them, f1 is the effective focal length of the first lens, f2 is the effective focal length of the second lens, f3 is the effective focal length of the third lens, f4 is the effective focal length of the fourth lens, f5 is the effective focal length of the fifth lens, f6 is the effective focal length of the sixth lens, TTL is the axial distance from the object side of the first lens to the imaging plane; f is the effective focal length of the ultra-wide-angle near-infrared imaging system, and F is the F number of the ultra-wide-angle near-infrared imaging system.

2. The ultra-wide-angle near-infrared imaging system according to claim 1, characterized in that The following relationship is satisfied: 23<Y1 / f<25; 8<Y2 / f<10; 230°<FOV<235°; Wherein, Y1 is the effective aperture of the object side (S1) of the first lens (G1), Y2 is the effective aperture of the object side (S3) of the second lens (L2), f is the effective focal length of the ultra-wide-angle near-infrared imaging system, and FOV is the maximum field of view of this ultra-wide-angle near-infrared imaging system.

3. The ultra-wide-angle near-infrared imaging system according to claim 1, characterized in that The following relationship is satisfied: 3.0<T12 / f<3.5; 3.5<T23 / f<4.0; 1.5<T34 / f<2.0; 0.08<T45 / f<0.1; 0.01<T56 / f<0.02; 0.30<T1 / ∑T<0.35; 0.10<T2 / ∑T<0.15; 0.25<T3 / ∑T<0.30; 0.05<T4 / ∑T<0.10; 0.10<T5 / ∑T<0.15; 0.10<T6 / ∑T<0.15; Among them, T12 is the air distance between the first lens and the second lens on the optical axis, T23 is the air distance between the second lens and the third lens on the optical axis, T34 is the air distance between the third lens and the fourth lens on the optical axis, T45 is the air distance between the fourth lens and the fifth lens on the optical axis, T56 is the air distance between the fifth lens and the sixth lens on the optical axis, and f is the effective focal length of the ultra-wide-angle near-infrared imaging system. ∑T is the sum of the lens thicknesses of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens on the optical axis, respectively, and T1, T2, T3, T4, T5, and T6 are the lens thicknesses of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens on the optical axis, respectively.

Images