Infrared lens

Abstract

The invention 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] The present invention belongs to the technical field of optical lenses, and more specifically, to infrared lenses. Background Art

[0002] With the rapid development of science and technology, infrared lenses are widely used in various fields such as commerce, industry and even agriculture. As a result, people's requirements for lenses will become higher and higher. In order to meet the current market demand, infrared lenses need to be applicable to different bands, have a smaller size, smaller distortion, better imaging quality and lower cost. The present invention is made to meet these requirements. Summary of the invention

[0003] This design aims to provide an infrared lens with small distortion and small TTL. Its advantages are small TTL, small volume, small distortion, the total length of the entire optical system is less than 7.1mm, and the invention only contains one optical glass lens, which effectively reduces the production cost. At the same time, the invention has good imaging quality.

[0004] To achieve the above object, the present invention adopts the following technical solutions:

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

[0006] The above infrared lens 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] Among them, 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 above infrared lens satisfies the following relationship:

[0015] 0.98<TTL / f<1.0;

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

[0017] The above infrared lens 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] Wherein, D is the aperture diameter of the infrared lens, f is the effective focal length of the 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), the second lens (L2), the third lens (L3), the fourth lens (L4), the fifth lens (L5), the sixth lens (L6) and the filter (IR) on the optical axis.

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

[0027] 2.3<F#<2.6;

[0028] Among them, F# is the F number of an infrared lens. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0031] Figure 3 This is an astigmatism curve diagram of the first embodiment of the present design; DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying 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. In addition, the technical features involved in the embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0033] like Figure 1 As shown, it is a schematic diagram of the structure of an infrared lens proposed by the present invention, and the infrared lens comprises eight parts from the object plane to the image plane in sequence: an aperture (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 a filter (IR). The first lens (G1) is a glass aspheric positive lens, whose object side surface is convex and whose image side surface is convex; the second lens (L2) is a plastic aspheric negative lens, whose object side surface is concave and whose image side surface is concave; the third lens (L3) is a plastic aspheric positive lens, whose object side surface is convex and whose image side surface is concave; the fourth lens (L4) is a plastic aspheric positive lens, whose object side surface is concave and whose image side surface is concave; the fifth lens (L5) is a plastic aspheric negative lens, whose object side surface is concave and whose image side surface is convex; and the sixth lens (L2) is a plastic aspheric positive lens, whose object side surface is convex and whose image side surface is concave.

[0034] The above infrared lens 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] Among them, 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] The present invention is conducive to reducing optical distortion and lowering its tolerance sensitivity when satisfying the above formulas (1) to (6); at the same time, the optical system only includes one optical glass lens and the object side surface (S4) and image side surface (S5) of the second lens (L2) are both concave lens structures, and the object side surface (S8) and image side surface (S9) of the fourth lens (L4) are both concave lens structures, so that the optical structure is compact, the total length of the optical system of an infrared lens is effectively reduced, and the miniaturization requirement is met.

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

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

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

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

[0047] The above infrared lens 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] Wherein, D is the aperture diameter of the infrared lens, f is the effective focal length of the 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), the second lens (L2), the third lens (L3), the fourth lens (L4), the fifth lens (L5), the sixth lens (L6) and the filter (IR) on the optical axis.

[0056] The aperture diameter of the present invention is relatively small, and when equation (8) is satisfied, the stray light and distortion of the infrared lens are effectively limited; at the same time, when equations (9) to (14) are satisfied, the thicknesses 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 reducing distortion while also reducing the tolerance sensitivity of the lens.

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

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

[0059] Among them, F# is the F number of an infrared lens.

[0060] The present invention can constrain the depth of field, magnification, resolution, distortion, and achieve higher imaging quality while satisfying formula (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 coefficients of an aspherical lens of an infrared lens

[0067]

[0068]

[0069]

[0070]

[0071]

[0072]

[0073] It will be easily understood by those skilled in the art that the above are only 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 in the protection scope of the present invention.

Claims

1. An infrared lens, comprising eight parts from the object plane to the image plane: an aperture (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 a filter (IR), wherein the first lens (G1) is a glass aspheric positive lens, whose object side surface is convex and whose image side surface is convex; the second lens (L2) is a plastic aspheric negative lens, whose object side surface is concave and whose image side surface is concave; the third lens (L3) is a plastic aspheric positive lens, whose object side surface is convex and whose image side surface is concave; the fourth lens (L4) is a plastic aspheric positive lens, whose object side surface is concave and whose image side surface is concave; the fifth lens (L5) is a plastic aspheric negative lens, whose object side surface is concave and whose image side surface is convex; and the sixth lens (L2) is a plastic aspheric positive lens, whose object side surface is convex and whose image side surface is concave.

2. An infrared lens as claimed in claim 1, characterized in that: The following relationship is 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; Among them, 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.

3. The infrared lens according to claim 1, characterized in that: The following relationship is satisfied: 0.98<TTL / f<1.0; Wherein, TTL is the distance on the optical axis from the object side surface (S2) of the first lens (L1) to the imaging surface (IMAGE), and f is the effective focal length of the infrared lens.

4. The infrared lens according to claim 1, characterized in that: The following relationship is 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; Wherein, D is the aperture diameter of the infrared lens, f is the effective focal length of the 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 total thickness of the first lens (G1), the second lens (L2), the third lens (L3), the fourth lens (L4), the fifth lens (L5), the sixth lens (L6) and the filter (IR) on the optical axis.

5. The infrared lens according to claim 1, characterized in that: The following relations are also satisfied: 2.3＜F#＜2.6； Among them, F# is the F number of an infrared lens.

Images