KR101274610B1 - 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 filter are provided from an object side to an image plane direction, and the first lens has a meniscus shape in which a surface opposing the object side is convex. It has a positive refractive power and both surfaces are formed aspherical, the second lens has a positive meniscus-shaped positive refractive power with a convex surface facing the first lens, and both surfaces are formed aspheric, and the filter filters far infrared rays. And the first lens and the second lens are 2.0 <n110 <3.0, 2.0 <n210 <3.0, 20 <v1 <200, 20 <v2 <200, f1> f2, 1 <f2 / f <1.6, 1 < f1 / f2 <2.5, v1 = (n110-1) / (n108-n112), v2 = (n210-1) / (n208-n212), and n110 at a wavelength of 10 μm of the first lens N108 is the refractive index at a wavelength of 8 μm of the first lens, n112 is the refractive index at the wavelength of 12 μm of the first lens, and n210 is a wavelength of 10 of the second lens. Is the index of refraction at, n208 is the index of refraction at wavelength 8 μm of the second lens, n212 is the index of refraction at wavelength 12 μm of the second lens, and f is the composite focus of the first and second lenses at a reference wavelength of 10 μm. Distance, f1 is the focal length of the first lens at the reference wavelength of 10 mu m, and f2 is the focal length of the second lens at the reference wavelength of 10 mu m. According to the lens unit for far-infrared cameras, the two lenses provide a simple structure and the desired performance, and can be molded by molding, thereby providing the advantages of easy manufacturing.

Description

Far-infrared camera lens unit

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens unit for a far infrared camera, and more particularly to a lens unit for a far infrared camera that can be easily manufactured by molding molding.

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.

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 non-light source surveillance cameras (CCTVs) that can operate without a light source in addition to automobiles, there is a need for a manufacturing technology that can be manufactured at a low cost and easy to manufacture a lens for condensing far-infrared light. Is increasing.

SUMMARY OF THE INVENTION 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 which is easy to manufacture by mold molding and has 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 filter sequentially from an object side to an image plane direction, and the first lens is opposed to the object side. It has a positive refractive power in the form of a meniscus having a first convex surface having a convex surface, and both surfaces thereof are formed aspherical, and the second lens has a second convex surface having a convex surface opposite to the first lens. It has positive refractive power in the form of meniscus, and both surfaces thereof are formed aspheric, and the filter transmits far infrared rays to the light passing through the second lens, and the first lens and the second lens have 2.0 <n110 <3.0. , 2.0 <n210 <3.0, 20 <v1 <200, 20 <v2 <200, f1> f2, 1 <f2 / f <1.6, 1 <f1 / f2 <2.5, wherein v1 = ( n110-1) / (n108-n112), v2 = (n210-1) / (n208-n212), and n110 is the first lens Is a refractive index at a wavelength of 10 μm, 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 wavelength of 10 μm of the second lens. Is the refractive index at, the n208 is the refractive index at a wavelength of 8 μm of the second lens, the n212 is the refractive index at a wavelength of 12 μm of the second lens, and f is the first and the second at a reference wavelength of 10 μm. It is a composite focal length of the second lens, f1 is the focal length of the first lens at a reference wavelength of 10 μm, and f2 is the focal length of the second lens at a reference wavelength of 10 μm.

Preferably, the diaphragm is provided between the first lens and the second lens.

In addition, the first lens and the second lens is molded by molding in a mold having a shape corresponding to the melting point of less than 350 ℃ material.

More preferably, the radius of curvature of the first convex surface opposite to the object side of the first lens is larger than the radius of curvature of the second convex surface opposite to the first lens of the second lens.

According to the lens unit for far-infrared cameras according to the present invention, the two lenses provide a simple structure and the desired performance, and can be molded by molding, thereby providing an 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, in the lens unit for a far infrared ray camera, a first lens L11, a second lens L21, and a filter 30 are sequentially provided in the direction of the image plane IMG from the object side OBJ.

The first lens L11 is formed in a meniscus shape having a first convex surface b1 having a convex surface facing the object side, and has a positive refractive power and both surfaces thereof are formed aspherical.

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 a planar portion C1 extending in a straight line in the vertical direction. In this case, the planar portion C1 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 second convex surface b2 having a convex surface facing the first lens L11, and has a positive refractive power and both surfaces are formed as an aspherical surface. .

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 second lens L21.

The diaphragm 50 is provided between the first lens L11 and the second lens L21.

In this lens unit, the first lens L11 and the second lens L21 are manufactured to satisfy the following conditions.

2.0 <n110 <3.0,

2.0 <n210 <3.0,

20 <v1 <200,

20 <v2 <200,

f1> f2,

1 <f2 / f <1.6,

1 <f1 / f2 <2.5

Here, v1 = (n110-1) / (n108-n112) and v2 = (n210-1) / (n208-n212).

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 is a refractive index at a wavelength of 10 μm of the second lens L21, n208 is a refractive index at a wavelength of 8 μm of the second lens L21, n212 is a wavelength of 12 μm at the second lens L21 Is the refractive index.

Also, f is a combined focal length of the first and second lenses L11 and L21 at a reference wavelength of 10 μm, f1 is a focal length of the first lens L11 at a reference wavelength of 10 μm, and f2 is a reference. The focal length of the second lens L21 at a wavelength of 10 μm.

The radius of curvature r1 of the first convex surface b1 facing the object side of the first lens L11 is opposite to the first lens L11 of the second lens L21. It is formed larger than the radius of curvature r2.

In addition, the first lens (L11) and the second lens (L21) is preferably formed by molding to a molding die of a corresponding shape, for this purpose is formed of a material having a melting point of less than 350 ℃.

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 and L21 constituting the lens unit shown in FIG. 1.

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 ∞ ∞ r1 19.47732 (aspherical) 6.500000 2.5858 101.01 r2 21.93225 (Aspherical) 1.253362 STO ∞ 7.547513 r3 15.28858 (Aspherical) 5.833488 2.5858 101.01 r4 23.69706 (Aspherical) 3.895709 r5 ∞ 1.100000 4.0034 1501.7 r6 ∞ 2.599966 IMG ∞ 0.000000

The coefficient values for the aspherical first lens L11 and the second lens L21 are shown in Table 2 below.

Aspheric coefficient K A B C D Aspheric surface (r1) -1.466997 -0.184941E-04 -0.376031E-06 0.838952E-10 -0.278915E-10 Aspheric surface (r2) -3.999604 -0.592102E-04 -0.110805E-05 -0.584163E-09 0.385717E-10 Aspheric surface (r3) -1.732220 0.396085E-04 -0.109696E-05 0.342257E-08 -0.480335E-09 Aspheric surface (r4) -7.816796 0.143963E-03 -0.145677E-05 -0.155171E-06 0.175881E-08

In addition, the values for the remaining parameters described above are shown in Table 3 below.

f f1 f2 n110 n108 n112 17.18 41.821 19.061 2.5858 2.5926 2.5769 n210 n208 n212 2.5858 2.5926 2.5769

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 and the second lens L22 sequentially give the second subscript corresponding to the embodiment with respect to the subscript given in the first embodiment.

Table 4 below shows the curvature radius, thickness, refractive index (N10), and Abbe's number (V10) for each lens L12 and L22 constituting the lens unit shown in FIG. 4.

The curved surface (ri) Radius of curvature Thickness or distance between lenses (di) Refractive Index (N10) Abbe number (V10) OBJ ∞ ∞ r1 20.24797 (Aspherical) 6.500000 2.5861 128.95 r2 23.01385 (Aspherical) 0.870579 STO ∞ 8.248146 r3 15.17445 (aspherical) 6.091822 2.5861 128.95 r4 22.25872 (Aspherical) 4.024432 r5 ∞ 1.100000 4.0034 1501.7 r6 ∞ 2.599966 IMG ∞ 0.000000

The coefficient values for the aspherical first lens L12 and the second lens L22 are shown in Table 5 below.

Aspheric coefficient K A B C D Aspheric surface (r1) -1.583712 -0.198338E-04 -0.361993E-06 0.131258E-09 -0.240535E-10 Aspheric surface (r2) -4.426921 -0.587607E-04 -0.100024E-05 0.504014E-09 0.241690E-10 Aspheric surface (r3) -1.647020 0.445236E-04 -0.798455E-06 0.123829E-10 -0.309435E-09 Aspheric surface (r4) -6.426523 0.159394E-03 -0.932715E-06 -0.146527E-06 0.155691E-08

In addition, the values for the remaining parameters described above are shown in Table 6 below.

f f1 f2 n110 n108 n112 17.54 43.51 19.68 2.5861 2.5917 2.5794 n210 n208 n212 2.5861 2.5917 2.5794

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 7 below shows the curvature radius, thickness, refractive index (N10), and Abbe's number (V10) for each lens L13 and L23 constituting the lens unit shown in FIG. 7.

The curved surface (ri) Radius of curvature Thickness or distance between lenses (di) Refractive Index (N10) Abbe number (V10) OBJ ∞ ∞ r1 18.65293 (aspherical) 6.000000 2.5858 101.01 r2 24.42310 (Aspherical) 3.630917 STO ∞ 6.692281 r3 13.46695 (aspherical) 6.000000 2.5858 101.01 r4 14.34008 (aspherical) 1.051061 r5 ∞ 1.000000 2.5858 101.01 r6 ∞ 3.000001 IMG ∞ 0.000000

The coefficient values for the aspherical first lens L13 and the second lens L23 are shown in Table 8 below.

Aspheric coefficient K A B C D Aspheric surface (r1) -0.671954 -0.100977E-04 -0.152973E-06 -0.476080E-09 -0.136310E-10 Aspheric surface (r2) -3.076441 -0.214262E-04 -0.325277E-06 -0.672544E-08 0.388236E-10 Aspheric surface (r3) -0.847812 0.831738E-04 -0.399116E-06 -0.100311E-07 -0.597112E-10 Aspheric surface (r4) 0.804031 0.401679E-03 -0.233365E-05 -0.250691E-07 0.161091E-08

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

f f1 f2 n110 n108 n112 17.05 30.40 26.75 2.5858 2.5926 2.5769 n210 n208 n212 2.5858 2.5926 2.5769

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 10 below shows the curvature radius, thickness, refractive index (N10), and Abbe's number (V10) for each lens L14 and L24 constituting the lens unit shown in FIG. 10.

The curved surface (ri) Radius of curvature Thickness or distance between lenses (di) Refractive Index (N10) Abbe number (V10) OBJ ∞ ∞ r1 21.08003 (Aspherical) 4.500000 2.5861 128.95 r2 35.06487 (Aspherical) 0.450000 STO ∞ 11.687370 r3 14.15171 (Aspherical) 5.656528 2.5861 128.95 r4 17.09281 (Aspherical) 0.791690 r5 ∞ 1.000000 4.0034 1501.7 r6 ∞ 2.599966 IMG ∞ 0.000000

The coefficient values for the aspherical first lens L14 and the second lens L24 are shown in Table 11 below.

Aspheric coefficient K A B C D Aspheric surface (r1) -1.803986 -0.224967E-04 -0.386139E-06 -0.103064E-08 -0.295871E-10 Aspheric surface (r2) -9.050924 -0.493523E-04 -0.665817E-06 -0.236512E-08 0.183853E-10 Aspheric surface (r3) -1.339872 0.422292E-04 -0.289509E-05 0.459447E-07 -0.990548E-09 Aspheric surface (r4) -1.541111 0.163103E-03 -0.943420E-05 -0.557821E-07 0.121879E-08

In addition, the values for the remaining parameters described above are shown in Table 12 below.

f f1 f2 n110 n108 n112 17.54 43.51 19.68 2.5861 2.5917 2.5794 n210 n208 n212 2.5861 2.5917 2.5794

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, the aspherical spin equation of Equation 1 below is satisfied for the aspherical first and second lenses.

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

Claims (6)

In the lens unit for a far infrared camera,
The first lens, the second lens and the filter are sequentially provided from the object side toward the image plane.
The first lens has a 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 an aspherical surface.
The second lens has positive refractive power in the form of a meniscus having a second convex surface having a convex surface opposite to the first lens, and both surfaces thereof are formed aspherical.
The filter transmits far infrared rays to the light passing through the second lens,
The first lens and the second lens
Satisfies the following conditions: 2.0 <n110 <3.0, 2.0 <n210 <3.0, 20 <v1 <200, 20 <v2 <200, f1> f2, 1 <f2 / f <1.6, 1 <f1 / f2 <2.5
Where v1 = (n110-1) / (n108-n112), v2 = (n210-1) / (n208-n212), n110 is a refractive index at a wavelength of 10 μm of the first lens, and 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, n210 is a refractive index at a wavelength of 10 μm of the second lens, and n208 is a second of the second lens A refractive index at a wavelength of 8 μm of the lens, n212 is a refractive index at a wavelength of 12 μm of the second lens, f is a combined focal length of the first and second lenses at a reference wavelength of 10 μm, and f1 Is a focal length of the first lens at a reference wavelength of 10 μm, and f2 is a focal length of the second lens at a reference wavelength of 10 μm. The lens structure according to claim 1, further comprising an aperture provided between the first lens and the second lens. 3. The lens structure of claim 2, wherein the first lens and the second lens are formed of a material having a melting point of less than 350 ° C. 4. The curvature radius of the first convex surface facing the object side of the first lens is larger than the curvature radius of the second convex surface facing the first lens of the second lens. Lens structure for far-infrared camera. The lens structure for a far infrared camera according to claim 4, wherein the first lens and the second lens are molded by molding in a mold having a corresponding shape. The lens structure for a far infrared camera according to claim 5, wherein the vertical end portions of the upper and lower ends of the image surface of the first lens have a planar portion extending linearly in the vertical direction.

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