KR101293217B1 - far-infrared camera lens unit - Google Patents

Abstract

The present invention relates to a lens unit for a far-infrared camera, wherein a first lens, a second lens, and a third lens are sequentially provided from an object side to an image plane direction, and the first lens has a convex surface facing the object side. It has positive refractive power of meniscus shape having one convex surface and both surfaces are spherical surfaces, the second lens has negative refractive power and both surfaces are spherical surfaces, and the third lens has convex surfaces opposite to the second lens. Has a positive refractive power of meniscus shape having a second convex surface, and the first to third lenses have 2.0 <n110 <4.2, 2.0 <n210 <3.0, 2.0 <n310 <3.0, 50 <v1 <1000, 20 <v2 <50, 50 <v3 <200, v3-v2> 50, v1-v2> 50, 1 <f1 / f3 <2.5, v1 = (n110-1) / (n108-n112), v2 = (n210-1) / (n208-n212), v3 = (n310-1) / (n308-n312), and n110, n210, and n310 are refractive indices at wavelengths of 10 μm of the first to third lenses, respectively. , n108, n208, n308 are the first to third lene A refractive index at each wavelength of 8 mu m, n112, n212, and n312 are refractive indices at a wavelength of 12 mu m of each of the first to third lenses, and f is a composite focal length of the first to third lenses at a reference wavelength of 10 mu m. F1 is the focal length of the first lens at the reference wavelength, and f3 is the focal length of the third lens at the reference wavelength. According to the lens unit for far-infrared cameras, three lenses can be molded by molding while having a simple structure and having a high resolution and low angle of view, thereby providing easy manufacturing.

Description

Far-infrared camera lens unit

The present invention relates to a lens unit for far-infrared cameras, and more particularly, to a lens unit for far-infrared cameras that can be easily manufactured by molding molding and has a high resolution and a low angle of view.

Far-infrared light is a light in the wavelength range of 8 micrometers-12 micrometers, and contains the infrared wavelength band which a human produces. Far-infrared cameras are cameras that can detect and capture infrared rays generated by humans or animals at night, and are disclosed in various ways such as Korean Patent No. 10-0415464.

On the other hand, it is preferable that the vehicle can recognize humans and animals that exist in the front at a speedy and accurate level to make driving safer at night.

Current cars are illuminated by the headlamps, and the driver recognizes the image of the road, vehicle, person, object, etc. in front of the vehicle by the reflected light. This approach recognizes the front by the visible reflected light. However, the method of recognizing by the visible reflected light has a problem in that the far side or the side side where the lamp does not reach is invisible, and the far infrared camera compensates for this.

The body temperature of humans and animals is about 310K, and the peak wavelength at 310K of black-body radiation is about 8 to 12 µm. Therefore, the existence of human beings can be known by capturing the far infrared rays emitted by humans and animals with a far infrared camera.

In addition, the far-infrared camera can also see the remote location outside the range of the lamp irradiation, the application of a combination of the far-infrared camera and the image processing device in the car can recognize the human or animals far away early. As a result, the safety of night driving of the vehicle is enhanced.

These far-infrared cameras for night observation are very expensive and are not popularized at present.

Therefore, there is a demand for a manufacturing technology that is easy to manufacture a lens for collecting far infrared light at a low cost.

In particular, considering that far infrared cameras can be used for various purposes, such as for a non-light source surveillance camera (CCTV) that can operate without a light source, it is inexpensive and easy to manufacture while providing a high resolution lens for condensing far infrared light. The need for manufacturing technology is increasing.

The present invention has been made to solve the above requirements, and an object thereof is to provide a lens unit for a far-infrared camera having a high resolution and a low angle of view and a simple structure.

In order to achieve the above object, the lens unit for a far-infrared camera according to the present invention is provided with a first lens, a second lens, and a third lens sequentially from an object side to an image plane direction, and the first lens is provided with the object side. It has a positive refractive power of meniscus shape having a convex first convex surface, and both surfaces are spherical surfaces, the second lens has a negative refractive power and both surfaces are spherical surfaces, and the third lens Meniscus-shaped positive refractive power having a convex second convex surface that is opposite to the second lens, and the first to third lenses are 2.0 <n110 <4.2, 2.0 <n210 <3.0, 2.0 < n310 <3.0, 50 <v1 <1000, 20 <v2 <50, 50 <v3 <200, v3-v2> 50, v1-v2> 50, 1 <f1 / f3 <2.5, where the above v1 = (n110-1) / (n108-n112), v2 = (n210-1) / (n208-n212), v3 = (n310-1) / (n308-n312), and n110 is the first lens Wavelength of 1 A refractive index at 0 μm, n108 is a refractive index at wavelength 8 μm of the first lens, n112 is a refractive index at wavelength 12 μm of the first lens, and n210 is a wavelength at 10 μm of the second lens Is a refractive index, and n208 is a refractive index at a wavelength of 8 μm of the second lens, n212 is a refractive index at a wavelength of 12 μm of the second lens, and n310 is a refractive index at a wavelength of 10 μm of the third lens. N308 is a refractive index at a wavelength of 8 μm of the third lens, n312 is a refractive index at a wavelength of 12 μm of the third lens, and f is a refractive index of the first to third lenses at a reference wavelength of 10 μm. It is a composite focal length, f1 is a focal length of the first lens at a reference wavelength of 10 μm, and f3 is a focal length of the third lens at a reference wavelength of 10 μm.

Preferably, the second lens and the third lens are formed of a material having a glass transition temperature of less than 350 ° C.

The distance between the center of the surface of the first lens that faces the second lens and the center of the surface of the second lens that faces the first lens is opposite to the third lens of the second lens. It is applied less than the distance to the center of the center and the middle third of the surface of the third lens facing the second lens.

The upper and lower end portions of the image side surface opposite to the second convex surface of the third lens may have a planar portion extending in a vertical direction in a vertical direction, and may face the first lens of the second lens. The surface is preferably formed concave.

And an aperture provided in the object-side direction of the first lens.

According to the lens unit for far-infrared cameras according to the present invention, three lenses can be molded by molding while the structure is simple and has a high resolution and low angle of view, thereby providing the advantage of easy manufacturing.

1 is a view showing a lens unit for a far infrared camera according to a first embodiment of the present invention,
FIG. 2 is an aberration diagram illustrating spherical aberration, image curvature, and distortion of the lens unit for the far-infrared camera of FIG. 1;
FIG. 3 is a graph of an MTF curve in which the spatial frequency of the far infrared camera lens of FIG.
4 is a view showing a lens unit for a far infrared ray camera according to a second embodiment of the present invention,
FIG. 5 is an aberration diagram illustrating spherical aberration, image curvature, and distortion of the lens unit for the far infrared camera of FIG. 4;
FIG. 6 is a graph of an MTF curve in which the spatial frequency of the far-infrared camera lens of FIG. 4 is represented by the horizontal axis and the ratio by the vertical axis, and the incident angle is a parameter.
7 is a view showing a lens unit for a far infrared camera according to a third embodiment of the present invention,
FIG. 8 is an aberration diagram illustrating spherical aberration, image curvature, and distortion of the lens unit for the far infrared camera of FIG. 7;
FIG. 9 is a graph of an MTF curve in which the spatial frequency of the far infrared camera lens of FIG.
10 is a view showing a lens unit for a far infrared ray camera according to a fourth embodiment of the present invention,
FIG. 11 is an aberration diagram illustrating spherical aberration, image curvature, and distortion of the lens unit for the far-infrared camera of FIG. 10.
FIG. 12 is a graph of an MTF curve in which the spatial frequency of the far infrared camera lens of FIG. 10 is the horizontal axis, the ratio is the vertical axis, and the incident angle is a parameter.

Hereinafter, a lens unit for a far infrared camera according to a preferred embodiment of the present invention with reference to the accompanying drawings will be described in more detail.

1 is a view showing a lens unit for a far infrared camera according to a first embodiment of the present invention.

Referring to FIG. 1, the lens unit for a far infrared camera includes a first lens L11, a second lens L21, a third lens L31, and a filter 30 from the object side OBJ toward the image plane IMG. Are provided sequentially.

The first lens L11 is formed in a meniscus shape having a first convex surface b1 having a convex surface opposite to the object side OBJ, and has a positive refractive power and both surfaces are spherical surfaces.

In the shape of the first lens L11, the upper and lower end portions of the upper and lower ends facing the image side surface are formed to have the planar portions C1 and C2 extending in the vertical direction in the vertical direction. In this case, the planar portions C1 and C2 may be formed in a region outside the portion functioning as the lens in consideration of the mountability.

The second lens L21 is formed in a meniscus shape having a first concave surface k1 having a concave surface facing the first lens L11, and has a negative refractive power and both surfaces thereof are spherical surfaces. .

The second lens L21 may have a concave surface different from the illustrated example, or may have a concave second concave surface k2 as shown in the confrontation with the third lens L31.

The third lens L31 has a second convex surface b2 having a convex surface opposite to the second lens L21, and has a concave third concave surface k3 facing the image side IMG. It is formed in the meniscus shape which has a positive refractive power, and both surfaces are formed in spherical surface.

The upper and lower end portions of the image side IMG surface opposite to the second convex surface b2 of the third lens L31 are formed to have planar portions c3 and c4 extending linearly in the vertical direction. In this case, the planar portions C3 and C4 may be formed in a region outside the portion functioning as the lens in consideration of the mountability.

The filter 30 is applied to protect the image sensor, and may be formed in a rectangular plate shape so as to transmit far infrared rays to light passing through the third lens L31.

The diaphragm 50 is provided in front of the first lens L11, that is, between the first lens L11 and the object side OBJ.

In the lens unit, the first lens L11 to the third lens L31 are manufactured to satisfy the following conditions.

2.0 <n110 <4.2,

2.0 <n210 <3.0,

2.0 <n310 <3.0,

50 <v1 <1000,

20 <v2 <50,

50 <v3 <200,

v3-v2> 50,

v1-v2> 50,

 1 <f1 / f3 <2.5 is satisfied.

Here, v1 = (n110-1) / (n108-n112), v2 = (n210-1) / (n208-n212), v3 = (n310-1) / (n308-n312).

Under the above conditions, v3-v2> 50 and v1-v2> 50 reduce chromatic aberration and provide high resolution for far infrared rays.

N110 is a refractive index at a wavelength of 10 μm of the first lens L11, n108 is a refractive index at a wavelength of 8 μm of the first lens L11, and n112 is a wavelength of 12 μm at the first lens L11. Refractive index, n210 (L21) is a refractive index at a wavelength of 10 μm of the second lens, n208 is a refractive index at a wavelength of 8 μm of the second lens L21, n212 is a wavelength of 12 μm of the second lens L21 N310 is a refractive index at a wavelength of 10 μm of the third lens L31, n308 is a refractive index at a wavelength of 8 μm of the third lens L31, and n312 is a 12 μm wavelength at the third lens L31. Refractive index at.

In addition, f is a combined focal length of the first to third lenses L11, L21 and L31 at a reference wavelength of 10 μm, f1 is a focal length of the first lens L11 at a reference wavelength of 10 μm, f2 is the focal length of the second lens L21 at the reference wavelength of 10 μm, and f3 is the focal length of the third lens L31 at the reference wavelength of 10 μm.

In addition, it is preferable that the third lens L31 is molded by molding to a mold having a corresponding shape.

In addition, the second lens L21 and the third lens L31 are formed of a material having a glass transition temperature Tg of less than 350 ° C.

Also, the distance S1 between the center of the surface of the first lens L11 that faces the second lens L21 and the center of the surface of the second lens L21 that faces the first lens L11 is the second. The distance between the center of the surface facing the third lens L31 of the lens L21 and the middle third of the surface facing the second lens L21 of the third lens L31 is smaller than the distance S2.

Such a lens unit also provides an advantage of providing a recognizable image even for a subject located at a distance of 1 km or more due to a small angle of view.

The present invention will be described in more detail with reference to the following examples.

First, Table 1 below shows the curvature radius, thickness, refractive index (N10), and Abbe's number (V10) for each lens L11, L21, and L31 constituting the lens unit shown in FIG.

Where N10 is a refractive index at 10 μm wavelength, V10 is (n10-1) / (n08-n12), n10 is a refractive index at 10 μm wavelength, n08 is a refractive index at 8 μm wavelength, n12 is 12 Refractive index at a μm wavelength.

The curved surface (ri) Radius of curvature Thickness or distance between lenses (di) Refractive index (n10) Abbe (v10) OBJ ∞ ∞ STO ∞ 0.100000 r1 66.19619 15.000000 2.5861 128.95 r2 129.55972 12.695061 r3 -808.23071 5.500000 2.724 29.22 r4 436.55196 43.611790 r5 24.22694 12.000000 2.5861 128.95 r6 24.35255 1.672109 r7 ∞ 1.100000 4.0034 1501.7 r8 ∞ 6.00013 IMG ∞ 0.000000

In addition, the values for the above-described parameters are shown in Table 2 below.

f f1 f2 f3 n110 n108 n112 57.5775 74.5171 -163.9561 49.6931 2.5861 2.5917 2.5794 n210 n208 n212 n310 n308 n312 2.724 2.746 2.687 2.5861 2.5917 2.5794

In addition, v1 is 128.95, v2 is 29.22, and v3 is 128.95.

The aberration diagram showing spherical aberration, image curvature and distortion for this lens unit is shown in FIG. That is, the aberration, the top surface curvature, and the percent distortion for light having a wavelength of 8 µm, 10 µm, and 12 µm for the 0.25 upper surface, the 0.50 upper surface, the 0.75 upper surface, and the 1.00 upper surface, respectively.

In addition, FIG. 3 is a graph showing MTF characteristics of an image height when a horizontal axis represents a spatial frequency, a vertical axis represents a ratio, and a parameter represents an angle of incidence with respect to the lens unit of FIG. 1.

As can be seen from Figures 2 and 3 it can be seen that the performance characteristics for the far infrared region is excellent.

4 is a view illustrating a lens unit according to a second exemplary embodiment of the present invention. Here, the first lens L12, the second lens L22, and the third lens L32 sequentially give the second subscript to the subscripts given in the first embodiment, corresponding to the embodiment.

Table 3 below shows the curvature radius, thickness, refractive index (N10) and Abbe's number (V10) for each lens L12, L22, and L32 constituting the lens unit shown in FIG.

The curved surface (ri) Radius of curvature Thickness or distance between lenses (di) Refractive index (n10) Abbe (v10) OBJ ∞ ∞ STO ∞ 0.100000 r1 74.41057 15.000000 2.5858 101.01 r2 228.17820 18.259013 r3 -270.42093 5.500000 2.724 29.22 r4 270.42093 39.633995 r5 23.06826 (Aspherical) 12.000000 2.5858 101.01 r6 26.93592 (aspherical) 2.132510 r7 ∞ 1.000000 4.0034 1501.7 r8 ∞ 5.999987 IMG ∞ 0.000000

The coefficient values for the aspherical third lens L32 are shown in Table 4 below.

Aspheric coefficient K A B C D Aspheric surface (r5) 0.158156 0.400038E-05 0.271128E-07 -0.409882E-10 0.555346E-12 Aspheric surface (r6) 2.244818 0.279684E-04 -0.147742E-06 0.516129E-08 0.112044E-12

In addition, the values for the remaining parameters described above are shown in Table 5 below.

f f1 f2 f3 n110 n108 n112 56.97 65.6994 -77.9268 34.9009 2.5858 2.5926 2.5769 n210 n208 n212 n310 n308 n312 2.724 2.746 2.687 2.5858 2.5926 2.5769

In addition, v1 is 101.01, v2 is 29.22, and v3 is 101.01.

The aberration diagrams showing spherical aberration, image curvature and distortion for this lens unit are shown in FIG. 5 and MTF characteristics.

As can be seen from FIGS. 5 and 6, it can be seen that the performance characteristics for the far infrared region are excellent.

7 is a diagram illustrating a lens unit according to a third exemplary embodiment of the present invention.

Table 6 below shows the curvature radius, thickness, refractive index (N10) and Abbe's number (V10) for each lens L13, L23, and L33 constituting the lens unit shown in FIG.

The curved surface (ri) Radius of curvature Thickness or distance between lenses (di) Refractive index (n10) Abbe (v10) OBJ ∞ ∞ STO ∞ 0.100000 r1 51.19585 5.500000 2.5861 128.95 r2 105.25326 8.180210 r3 -191.49059 5.500000 2.724 29.22 r4 -749.74482 31.789495 r5 25.00869 13.937813 2.5861 128.95 r6 31.97984 1.353210 r7 ∞ 1.100000 4.0034 1501.7 r8 ∞ 6.000010 IMG ∞ 0.000000

In addition, the values for the above-described parameters are shown in Table 7 below.

f f1 f2 f3 n110 n108 n112 36.7404 59.1556 -150.1094 32.4908 2.5861 2.5917 2.5794 n210 n208 n212 n310 n308 n312 2.724 2.746 2.687 2.5861 2.5917 2.5794

In addition, v1 is 128.95, v2 is 29.22, and v3 is 128.95.

Aberration diagrams showing spherical aberration, image curvature, and distortion for these lens units are shown in FIG. 8 and MTF characteristics.

As can be seen from FIGS. 8 and 9, it can be seen that the performance characteristics for the far-infrared region are excellent.

10 is a view showing a lens unit according to a fourth embodiment of the present invention.

Table 8 below shows the curvature radius, thickness, refractive index (N10) and Abbe's number (V10) for each lens L14, L24, and L34 constituting the lens unit shown in FIG.

The curved surface (ri) Radius of curvature Thickness or distance between lenses (di) Refractive index (n10) Abbe (v10) OBJ ∞ ∞ STO ∞ 0.100000 r1 83.42856 9.944127 4.003073 942.29 r2 109.51875 12.289868 r3 -110.27753 12.550584 2.724 29.22 r4 -123.04250 44.512757 r5 37.35305 13.000000 2.5861 128.95 r6 49.51339 1.395157 r7 ∞ 1.100000 4.0034 1501.7 r8 ∞ 10.999955 IMG ∞ 0.000000

In addition, the values for the above-described parameters are shown in Table 9 below.

f f1 f2 f3 n110 n108 n112 57.6998 90.686451 -1632.28557 57.916122 4.003073 4.005260 4.002073 n210 n208 n212 n310 n308 n312 2.724 2.746 2.687 2.5861 2.5917 2.5794

In addition, v1 is 942.29, v2 is 29.22, and v3 is 128.95.

Aberration diagrams showing spherical aberration, image curvature, and distortion for these lens units are shown in FIG. 11 and MTF characteristics.

As can be seen from FIGS. 11 and 12, it can be seen that the performance characteristics for the far-infrared region are excellent.

On the other hand, for an aspherical lens, the aspherical spinning equation of Equation 1 below is satisfied.

Where x is the distance from the vertex of the lens in the optical axis direction, y is the distance in the direction perpendicular to the optical axis, c 'is the inverse of the radius of curvature r at the vertex of the lens (= 1 / r), K is conic Is a (Conic) constant, and A, B, C, and D are aspherical coefficients.

L11, L12, L13, L14: first lens
L21, L22, L23, L24: second lens
L31, L32, L33, L34: Third lens

Claims (7)

In the lens unit for a far infrared camera,
The first lens, the second lens, and the third lens are sequentially provided from the object side toward the image plane;
The first lens has positive refractive power of meniscus shape having a first convex surface having a convex surface facing the object side, and both surfaces thereof are formed as spherical surfaces.
The second lens has a negative refractive power and both surfaces are spherical,
The third lens has a positive meniscus refractive power having a second convex surface having a convex surface opposite to the second lens.
The first to third lenses
2.0 <n110 <4.2, 2.0 <n210 <3.0, 2.0 <n310 <3.0,
50 <v1 <1000, 20 <v2 <50, 50 <v3 <200, v3-v2> 50, v1-v2> 50, 1 <f1 / f3 <2.5
Wherein v1 = (n110-1) / (n108-n112), v2 = (n210-1) / (n208-n212), v3 = (n310-1) / (n308-n312), and n110 is the A refractive index at a wavelength of 10 μm of the first lens, n108 is a refractive index at a wavelength of 8 μm of the first lens, n112 is a refractive index at a wavelength of 12 μm of the first lens, and n210 is a value of the second lens A refractive index at a wavelength of 10 μm, n208 is a refractive index at a wavelength of 8 μm of the second lens, n212 is a refractive index at a wavelength of 12 μm of the second lens, and n310 is a wavelength of 10 of the third lens A refractive index at a micrometer, n308 is a refractive index at a wavelength of 8 μm of the third lens, n312 is a refractive index at a wavelength of 12 μm of the third lens, and f1 is the first at a reference wavelength of 10 μm The focal length of the lens, wherein f3 is the focal length of the third lens at a reference wavelength of 10㎛. The lens unit of claim 1, wherein the second lens and the third lens are formed of a material having a glass transition temperature of less than 350 ° C. 3. The third lens of claim 2, wherein a distance between a center of a surface of the first lens that faces the second lens and a center of a surface of the second lens that faces the first lens is determined by the third lens of the second lens. And a distance between the center of the surface opposite to the center and the middle third of the surface opposite to the second lens of the third lens. The lens unit for a far infrared camera according to claim 3, wherein the third lens is molded by molding in a shaping mold having a corresponding shape. The lens for a far-infrared camera according to claim 4, wherein the upper and lower end portions of the third lens facing the image surface opposite to the second convex surface have a planar portion extending linearly in the vertical direction. Unit. The lens unit for a far infrared camera according to claim 5, wherein the surface of the second lens facing the first lens is concave. The lens unit for a far-infrared camera according to claim 6, further comprising an aperture provided in an object-side direction of the first lens.

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