Infrared lens

Abstract

The utility model discloses an infrared lens, which belongs to the field of optical lenses and comprises a diaphragm (STO), a first lens (G1), a second lens (L2), a third lens (L3), a fourth lens (L4), a fifth lens (L5), a sixth lens (L6) and an optical filter (IR), and the focal lengths of the lens elements meet the following relational expression: 0.35 lt; f1 / flt; 0.45, 0.45; -0.4 lt,-0.4 lt; f2 / flt; -0.3,-0.3; 4.0 lt; f3 / flt; 5.0); 11 lt; f4 / flt; 12; -1.0 lt; f5 / flt; 0; 1.0 lt; f6 / flt; 2.0. The infrared lens is small in size, and the second lens and the fourth lens are both biconcave lenses, so that the structure is more compact. The lens is small in F number, good in tolerance, small in distortion, good in imaging effect, low in production cost and feasible in mass production due to the fact that only one glass lens is arranged.

Description

Technical Field

[0001] This design belongs to the field of optical lens technology, and more specifically, relates to infrared lenses. Background Technology

[0002] With the rapid development of technology, infrared lenses have been widely used in various fields such as commerce, industry, and even agriculture. As a result, people's requirements for lenses are getting higher and higher. In order to meet the current market demand, infrared lenses need to be applicable to different wavelengths, have smaller size, less distortion, better image quality, and lower cost. This invention was made to meet these requirements. Summary of the Invention

[0003] This design aims to provide an infrared lens with low distortion and low TTL. Its advantages include low TTL, small size, and low distortion. The total length of the entire optical system is less than 7.1mm, and the invention contains only one optical glass lens, effectively reducing production costs. Furthermore, this invention provides excellent image quality.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] An infrared lens comprises eight parts from the object plane to the image plane: an aperture stop (STO), a first lens (G1), a second lens (L2), a third lens (L3), a fourth lens (L4), a fifth lens (L5), a sixth lens (L6), and an IR filter. The first lens (G1) is a glass aspherical positive lens with a convex object-side surface and a convex image-side surface. The second lens (L2) is a plastic aspherical negative lens with a concave object-side surface and a concave image-side surface. The third lens (L3) is a plastic aspherical positive lens with a convex object-side surface and a concave image-side surface. The fourth lens (L4) is a plastic aspherical positive lens with a concave object-side surface and a concave image-side surface. The fifth lens (L5) is a plastic aspherical negative lens with a concave object-side surface and a convex image-side surface. The sixth lens (L2) is a plastic aspherical positive lens with a convex object-side surface and a concave image-side surface.

[0006] The infrared lens mentioned above satisfies the following relationship:

[0007] 0.35 <f1 / f<0.45;

[0008] -0.45 <f2 / f<-0.3;

[0009] 4.0 <f3 / f<5.0;

[0010] 11 <f4 / f<12;

[0011] -2.0 <f5 / f<0;

[0012] 1.0 <f6 / f<2.0;

[0013] Wherein, f1 is the effective focal length of the first lens (G1), f2 is the effective focal length of the second lens (L2), f3 is the effective focal length of the third lens (L3), f4 is the effective focal length of the fourth lens (L4), f5 is the effective focal length of the fifth lens (L5), f6 is the effective focal length of the sixth lens (L6), and f is the effective focal length of an infrared lens.

[0014] The infrared lens mentioned above satisfies the following relationship:

[0015] 0.98 < TTL / f < 1.0;

[0016] Where TTL is the distance on the optical axis from the object side (S1) of the first lens (L1) to the imaging surface (IMAGE), and f is the effective focal length of the infrared lens.

[0017] The infrared lens mentioned above satisfies the following relationship:

[0018] 0.4 < D / f < 1;

[0019] 0.3 < T1 / ∑T < 0.4;

[0020] 0.07 < T² / ∑T < 0.12;

[0021] 0.1 < T3 / ∑T < 0.12;

[0022] 0.1 < T⁴ / ∑T < 0.12;

[0023] 0.08 < T5 / ∑T < 0.12;

[0024] 0.2 < T6 / ∑T < 0.22;

[0025] Where D is the aperture diameter of this infrared lens, and f is the effective focal length of this infrared lens. T1 is the thickness of the first lens (G1) on the optical axis, T2 is the thickness of the second lens (L2) on the optical axis, T3 is the thickness of the third lens (L3) on the optical axis, T4 is the thickness of the fourth lens (L4) on the optical axis, T5 is the thickness of the fifth lens (L5) on the optical axis, T6 is the thickness of the sixth lens (L6) on the optical axis, and ∑T is the sum of the thicknesses of the first lens (G1), second lens (L2), third lens (L3), fourth lens (L4), fifth lens (L5), sixth lens (L6) and filter (IR) on the optical axis.

[0026] The infrared lens mentioned above satisfies the following relationship:

[0027] 2.3 < F# < 2.6;

[0028] F# is the F-number of an infrared lens. Attached Figure Description

[0029] Figure 1 This is a structural schematic diagram of the first embodiment of this design;

[0030] Figure 2 This is a distortion diagram of the first embodiment of this design;

[0031] Figure 3 This is the astigmatism curve diagram of the first embodiment of this design; Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0033] like Figure 1 The diagram shows a schematic of the structure of an infrared lens proposed in this invention. It comprises eight parts from the object plane to the image plane: an aperture stop (STO), a first lens (G1), a second lens (L2), a third lens (L3), a fourth lens (L4), a fifth lens (L5), a sixth lens (L6), and an IR filter. The first lens (G1) is a glass aspherical positive lens with a convex object-side surface and a convex image-side surface. The second lens (L2) is a plastic aspherical negative lens with a concave object-side surface and a concave image-side surface. The third lens (L3) is a plastic aspherical positive lens with a convex object-side surface and a concave image-side surface. The fourth lens (L4) is a plastic aspherical positive lens with a concave object-side surface and a concave image-side surface. The fifth lens (L5) is a plastic aspherical negative lens with a concave object-side surface and a convex image-side surface. The sixth lens (L2) is a plastic aspherical positive lens with a convex object-side surface and a concave image-side surface.

[0034] The infrared lens mentioned above satisfies the following relationship:

[0035] 0.35 <f1 / f<0.45; (1)

[0036] -0.45 <f2 / f<-0.3; (2)

[0037] 4.0 <f3 / f<5.0; (3)

[0038] 11 <f4 / f<12; (4)

[0039] -2.0 <f5 / f<0; (5)

[0040] 1.0 <f6 / f<2.0 (6)

[0041] Wherein, f1 is the effective focal length of the first lens (G1), f2 is the effective focal length of the second lens (L2), f3 is the effective focal length of the third lens (L3), f4 is the effective focal length of the fourth lens (L4), f5 is the effective focal length of the fifth lens (L5), f6 is the effective focal length of the sixth lens (L6), and f is the effective focal length of an infrared lens.

[0042] Under the condition of satisfying the above (1)-(6), the present invention is beneficial to reduce optical distortion and reduce its tolerance sensitivity; at the same time, the optical system contains only one optical glass lens and the second lens (L2) has a concave lens structure with the object side (S4) and image side (S5) being concave, and the fourth lens (L4) has a concave lens structure with the object side (S8) and image side (S9) being concave, making the optical structure compact and effectively reducing the total length of the optical system of an infrared lens, thus meeting the miniaturization requirements.

[0043] The infrared lens mentioned above satisfies the following relationship:

[0044] 0.98 < TTL / f < 1.0; (7)

[0045] Where TTL is the distance on the optical axis from the object side (S2) of the first lens (L1) to the imaging plane (IMAGE), and f is the effective focal length of this infrared lens.

[0046] The present invention can limit the working distance to a shorter distance while having a smaller distortion when satisfying equation (7).

[0047] The infrared lens mentioned above satisfies the following relationship:

[0048] 0.4 < D / f < 1; (8)

[0049] 0.3 < T1 / ∑T < 0.4; (9)

[0050] 0.07 < T2 / ∑T < 0.12; (10)

[0051] 0.1 < T3 / ∑T < 0.12; (11)

[0052] 0.1 < T4 / ∑T < 0.12; (12)

[0053] 0.08 < T5 / ∑T < 0.12; (13)

[0054] 0.2 < T6 / ∑T < 0.22; (14)

[0055] Where D is the aperture diameter of this infrared lens, and f is the effective focal length of this infrared lens. T1 is the thickness of the first lens (G1) on the optical axis, T2 is the thickness of the second lens (L2) on the optical axis, T3 is the thickness of the third lens (L3) on the optical axis, T4 is the thickness of the fourth lens (L4) on the optical axis, T5 is the thickness of the fifth lens (L5) on the optical axis, T6 is the thickness of the sixth lens (L6) on the optical axis, and ∑T is the sum of the thicknesses of the first lens (G1), second lens (L2), third lens (L3), fourth lens (L4), fifth lens (L5), sixth lens (L6) and filter (IR) on the optical axis.

[0056] The aperture diameter of this invention is relatively small, which effectively limits stray light and distortion of the infrared lens when satisfying equation (8); at the same time, when satisfying equations (9)-(14), the thickness of the first lens (L2), the third lens (L3), the fourth lens (L4) and the fifth lens (L5) are moderate and reasonably distributed, which is beneficial to reduce distortion and also reduces the tolerance sensitivity of the lens.

[0057] The infrared lens mentioned above satisfies the following relationship:

[0058] 2.3 < F# < 2.6; (15)

[0059] F# is the F-number of an infrared lens.

[0060] The present invention can constrain depth of field, magnification, resolution, distortion, and achieve higher imaging quality when satisfying equation (15).

[0061] Example 1

[0062] As a specific embodiment of the present invention, the parameters of an infrared lens are shown in Table 1 below:

[0063] Table 1. Structural parameters of an infrared lens

[0064]

[0065]

[0066] Table 2. Surface coefficient of aspherical lens for an infrared lens.

[0067]

[0068]

[0069]

[0070]

[0071]

[0072]

[0073] Those skilled in the art will readily understand that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An infrared lens comprising eight parts from the object plane to the image plane: an aperture stop (STO), a first lens (G1), a second lens (L2), a third lens (L3), a fourth lens (L4), a fifth lens (L5), a sixth lens (L6), and an IR filter, wherein the first lens (G1) is a glass aspherical positive lens with a convex object-side surface and a convex image-side surface; the second lens (L2) is a plastic aspherical negative lens with a concave object-side surface and a concave image-side surface; the third lens (L3) is a plastic aspherical positive lens with a convex object-side surface and a concave image-side surface; the fourth lens (L4) is a plastic aspherical positive lens with a concave object-side surface and a concave image-side surface; the fifth lens (L5) is a plastic aspherical negative lens with a concave object-side surface and a convex image-side surface; and the sixth lens (L6) is a plastic aspherical positive lens with a convex object-side surface and a concave image-side surface, characterized in that… The following relationship must be satisfied: 0.35 <f1 / f<0.45; -0.45 <f2 / f<-0.3; 4.0 <f3 / f<5.0; 11 <f4 / f<12; -2.0 <f5 / f<0; 1.0 <f6 / f<2.0; Wherein, f1 is the effective focal length of the first lens (G1), f2 is the effective focal length of the second lens (L2), f3 is the effective focal length of the third lens (L3), f4 is the effective focal length of the fourth lens (L4), f5 is the effective focal length of the fifth lens (L5), f6 is the effective focal length of the sixth lens (L6), and f is the effective focal length of an infrared lens.

2. An infrared lens as described in claim 1, characterized in that, The following relationship must be satisfied: 0.98 < TTL / f < 1.0; Where TTL is the distance on the optical axis from the object side (S2) of the first lens (G1) to the imaging surface (IMAGE), and f is the effective focal length of the infrared lens.

3. An infrared lens as described in claim 1, characterized in that, The following relationship must be satisfied: 0.4 < D / f < 1; 0.3 < T1 / ∑T < 0.4; 0.07 < T² / ∑T < 0.12; 0.1 < T3 / ∑T < 0.12; 0.1 < T⁴ / ∑T < 0.12; 0.08 < T5 / ∑T < 0.12; 0.2 < T6 / ∑T < 0.22; Where D is the aperture diameter of this infrared lens, f is the effective focal length of this infrared lens, T1 is the thickness of the first lens (G1) on the optical axis, T2 is the thickness of the second lens (L2) on the optical axis, T3 is the thickness of the third lens (L3) on the optical axis, T4 is the thickness of the fourth lens (L4) on the optical axis, T5 is the thickness of the fifth lens (L5) on the optical axis, T6 is the thickness of the sixth lens (L6) on the optical axis, and ∑T is the sum of the thicknesses of the first lens (G1), second lens (L2), third lens (L3), fourth lens (L4), fifth lens (L5), sixth lens (L6) and filter (IR) on the optical axis.

4. An infrared lens as described in claim 1, characterized in that, It also satisfies the following relation: 2.3＜F#＜2.6； F# is the F-number of an infrared lens.

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