TWI625968B - Long-wavelength infrared camera with 21 degree angle of view and lens for the camera - Google Patents

Abstract

The present invention relates to a long-wavelength infrared camera and a lens for a camera having a 21-degree horizontal viewing angle, wherein the molding is formed of an optical material, comprising: a concave surface (R2) for performing first light incident from a subject a secondary refraction; and a convex surface (R3) for secondarily refracting light passing through the concave surface (R2), wherein the concave surface (R2) and the convex surface (R3) are in accordance with the relationship of Equation 1, Table 1, and Table 2 below. set:

Where k is the conic surface coefficient, A4, A6, A8, and A10 are aspherical coefficients, h is the distance from the optical axis to the concave or convex surface, and c is the central curvature.

Among them, the radius of curvature and the surface thickness have a tolerance of ±0.5%, (the diameter of the concave surface (R2)) / (the diameter of the convex surface (R3)) is 0.57 (±0.5% tolerance).

Description

Long-wavelength infrared camera and camera lens with 21-degree horizontal viewing angle

The present invention relates to a long-wavelength infrared camera and a camera lens having a 21-degree horizontal viewing angle, and more particularly to a popular long-wavelength infrared (also known as "LWIR") camera and a camera lens that can be used in various security surveillance fields.

Long-wavelength infrared rays are light having a wavelength of 8 μm to 12 μm, including the wavelength range of infrared rays emitted by humans.

Long-wavelength infrared cameras are cameras that can be imaged by detecting infrared rays emitted by humans or animals at night.

The body temperature of human or animal is about 310K, and the peak wavelength of 310K of black body radiation is 8μm~12μm.

Therefore, it is possible to judge whether or not humans or animals are present and to acquire images by infrared energy emitted from humans or animals by a long-wavelength infrared camera.

However, in the case of South Korea, the development of long-wavelength infrared-specific lenses and long-wavelength infrared camera systems is extremely slow, so the actual situation is mostly dependent on imports and sold at high prices.

In particular, since the conventional infrared camera is mainly manufactured by a direct processing lens based on a Germanium lens, the manufacturing cost is high and the manufacturing time is long.

Therefore, the Xenon lens is mainly used in the military field, and the price is in the civilian sector. The grid problem is rarely used.

[Previous Technical Literature] [Patent Literature]

Patent Document 1: Korean Patent Publication No. 10-0916502 B1 (September 01, 2009)

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems of the prior art, and an object of the present invention is to provide an optical material suitable for molding, which can reduce production cost and can be easily produced by mass production as compared with a conventional xenon lens. A long-wavelength infrared camera and camera lens with a 21-degree horizontal viewing angle for the civilian sector.

In order to achieve the above object, the lens for a long-wavelength infrared camera having a 21-degree horizontal viewing angle of the present invention is a lens having a 21-degree horizontal viewing angle, that is, it is formed of a molding optical material, including: a concave surface R2, a first refraction of light incident from the object; and a convex surface R3 for second refraction of light passing through the concave surface R2, wherein the concave surface R2 and the convex surface R3 are according to the following formula 1, Table 1 and According to the relationship of Table 2:

Where k is the conic surface coefficient, A4, A6, A8, and A10 are aspherical coefficients, h is the distance from the optical axis to the concave or convex surface, and c is the central curvature.

Here, the radius of curvature and the surface thickness have a tolerance of ±0.5%, (the diameter of the concave surface R2) / (the diameter of the convex surface R3) is 0.57 (±0.5% tolerance).

The present invention is characterized in that the lens is formed with an edge portion extending from the concave surface R2 and the convex surface R3 in a direction perpendicular to the optical axis.

The present invention is characterized in that (the average value of the central portion thickness TC/diameter of the concave surface R2 and the convex surface R3) is 0.79 (±0.5% tolerance), (thickness of the edge portion of the lens) / (the concave portion R2 and the center portion of the convex surface R3) The thickness TC) is 0.74 (±0.5% tolerance).

Further, the long-wavelength infrared camera having a 21-degree horizontal viewing angle of the present invention includes: an aperture; the lens; an infrared filter disposed apart from the convex surface R3; and a sensing surface through which the infrared filter is filtered The light of the device is used to image the subject.

The present invention is characterized in that the distance between the aperture and the concave surface R2 is 0.7 mm ± 0.5%, and the thickness TC of the central portion of the concave surface R2 and the convex surface R3 is 6.295 mm ± 0.5%, from the convex surface R3 to the infrared filter. The distance is 6.7 mm ± 0.5%, the thickness of the infrared filter is 0.65 mm ± 0.5%, the distance from the above infrared filter to the sensing surface is 1.3 mm ± 0.5%, and the refractive index of the above filter is 3.421. The dispersion rate was 2421.0.

According to the invention of the structure as described above, in the field of security monitoring, For the popular optical system, it is possible to detect organisms or things with only one lens, so that it can be applied to various fields (night safety monitoring, fire prevention, transformer detection, etc.).

Further, according to the present invention, it is a structure which can be molded, which is easy to manufacture and can be mass-produced, and has an advantage of being inexpensive to manufacture.

100‧‧‧ aperture

200‧‧‧ lens

210‧‧‧Edge

300‧‧‧Infrared filter

400‧‧‧ Sensing surface

1000‧‧‧Long-wavelength infrared camera with 21 degree horizontal viewing angle

R2‧‧‧ concave

R3‧‧‧ convex

1(a) and (b) are perspective views of a long wavelength infrared camera having a 21 degree horizontal viewing angle of the present invention.

Fig. 2 is a structural view showing the structure of the optical system of Fig. 1.

3 is a light trace analysis diagram of a long wavelength infrared camera having a 21 degree horizontal viewing angle of the present invention.

4 is a graph showing longitudinal spherical abberration of a long wavelength infrared camera having a 21 degree horizontal viewing angle of the present invention.

Fig. 5 is a diagram showing aberration analysis relating to astigmatism of a long-wavelength infrared camera having a 21 degree horizontal viewing angle of the present invention.

Fig. 6 is a graph showing distortion of a long wavelength infrared camera having a 21 degree horizontal viewing angle of the present invention.

Fig. 7 is a graph showing a modulation transfer function (MTF) showing the resolution of a long-wavelength infrared camera having a 21 degree horizontal viewing angle of the present invention.

Fig. 8 is a view showing a spot diagram of a long wavelength infrared camera having a 21 degree horizontal viewing angle of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

As shown in FIG. 1 and FIG. 2, the long-wavelength infrared camera 1000 having a 21-degree horizontal viewing angle of the present invention includes: an aperture 100; a lens 200 including a concave surface R2 and a convex surface R3 for injecting from a subject The light is first refracted, the convex surface R3 is used for second refracting the light passing through the concave surface R2; the infrared ray filter 300 is disposed apart from the convex surface R3; and the sensing surface 400 is passed through the infrared ray The light of the filter 300 images the subject.

First, the diaphragm 100 disposed on the front surface of the convex surface R3 performs an action of preventing the stray light from entering the optical system of the present invention.

The above-described lens 200 having a 21 degree horizontal viewing angle is formed of a molded optical material.

The optical material for molding is formed of glass or plastic, and is preferably made of an ultra-small aperture lens by using a material having a high refractive index and a lens transmission characteristic as compared with a similar type of material which has been commercially available. Material for a variety of optical systems to medium-caliber lenses.

For example, a lens material suitable for the optical system design of the present invention is a molding material such as Ge _27.5 -Sb _13.5 -Se _60, and a refractive index of 2.5 or more and a wavelength band of up to 12 μm can be used. Highly transmissive material.

When the optical system of the optical material of the present invention is used, it is possible to embody a clear image and to perform molding based molding, thereby constituting a simple and low-cost safety monitoring and popular long-wavelength infrared ray. Camera optical system.

Further, the long-wavelength infrared camera 1000 having a 21-degree horizontal viewing angle of the present invention performs optical design of one set of one popular long-wavelength infrared rays to which 6400 primitives (sensors) are applied.

The optical system of the present invention increases the center portion of the lens and the edge portion 210 The thickness is such that it is in a form that is advantageous for molding.

Further, the concave surface R2 and the convex surface R3 of the lens 200 of the present invention are determined according to the relationship of the following formula 1.

Where k is the conic surface coefficient, A4, A6, A8, and A10 are aspherical coefficients, h is the distance from the optical axis to the concave or convex surface, and c is the central curvature.

As shown in Table 1 below, the concave surface R2 and the convex surface R3 are defined by determining the aspherical coefficient.

Further, as shown in Table 2 below, the curvature radius RC and the surface thickness ST of the concave surface R2 and the convex surface R3 of the lens 200 are set, and the refractive index n and the dispersion ratio v1 are determined.

The above dispersion ratio v1 is determined by the following formula.

[Formula 2] v1=(n110-1)/(n108-n112)

Wherein n110 is a refractive index of one lens having a wavelength of 10 μm, n108 is a refractive index of one lens having a wavelength of 8.0 μm, and n112 is a refractive index of one lens having a wavelength of 12 μm, and 2.0<n110<3.0

Among them, the radius of curvature and the thickness of the face may have a tolerance of ±0.5%.

In particular, the value of (the diameter of the concave surface R2) / (the diameter of the convex surface R3) is 0.57 (±0.5% tolerance), (the thickness of the edge portion of the lens) / (the thickness of the central portion TC of the concave surface R2 and the convex surface R3) It is 0.74 (±0.5% tolerance), so the angle of view of 21 degrees can be accurately adjusted.

Further, since the thickness of the center portion and the edge portion of the lens is thick, it can be in a form advantageous for molding.

According to the present invention, the distance between the diaphragm and the concave surface R2 can be set to 0.7 mm ± 0.5%, and the central portion thickness TC of the concave surface R2 and the convex surface R3 can be set to 6.295 mm ± 0.5%, from the convex surface R3 to the infrared filter. The distance of the optical device 300 is set to 6.7 mm ± 0.5%, the thickness of the infrared filter 300 is set to 0.65 mm ± 0.5%, and the distance from the infrared filter 300 to the sensing surface 400 is set to 1.3 mm ± 0.5%.

If the thickness tolerance is set in the lens 200 of the present invention, it can be manufactured within the allowable tolerance of the manufactured lens, so that a lens having a predetermined optical performance can be manufactured.

Further, the edge portion of the lens 200 is manufactured in a circular arc shape, which facilitates assembly and manufacture of the optical system.

On the other hand, preferably, the infrared filter 300 has a refractive index of 3.421 and a dispersion ratio of 2421.0.

By the above conditions, a predetermined viewing angle can be obtained and longitudinal spherical aberration, astigmatism, and distortion aberration can be minimized, and a good state can be obtained within the value of the modulation transfer function indicating the resolution.

An exemplary embodiment of the long wavelength infrared camera 1000 having a 21 degree horizontal viewing angle of the present invention is described based on the configuration as described above.

First, the lens 200 of the long-wavelength infrared camera having a 21-degree horizontal viewing angle of the present invention is a lens of a long-wavelength infrared camera optical system applicable to the field of security monitoring, by applying a non-form formed by Ge _27.5 - Sb _{13.5 -} Se ₆₀ Oxide infrared optical glass is used for molding.

Further, the curvature radius of the concave surface R2 and the convex surface R3 of the lens 200 is set to -17.7265 mm (aspheric surface), -8.1644 mm (aspheric surface), and the diameter of the concave surface R2 is set to 5.78 mm, and the diameter of the convex surface R3 is set to 10.2. Mm.

The entire lens 200 forms a thickness of 6.935 mm.

For the mounting, the edge portion 210 extending from the concave surface R2 and the convex surface R3 in the direction perpendicular to the optical axis is formed. When the edge portion 210 is considered, the diameter of the entire lens is set to 15.8 mm.

The length of the above-described edge portion 210 can be appropriately adjusted.

An arcuate portion of 0.3 to 0.6 mm is formed at an edge portion of the edge portion 210.

The concave surface R2 and the convex surface R3 of the lens 200 are formed by the above formula 1 and Table 1 and Table 2.

Further, the central portion thickness TC of the concave surface R2 and the convex surface R3 was set to 6.295 mm, respectively, and the thickness of the edge portion of the lens was set to 4.635.

Further, the distance between the diaphragm 100 and the concave surface R2 is set to 0.7 mm, the distance from the convex surface R3 to the infrared filter 300 is set to 6.7 mm, and the thickness of the infrared filter 300 is set to 0.65 mm. The distance from the infrared filter 300 to the sensing surface 400 was set to 1.3 mm.

The above infrared filter 300 having a refractive index of 3.421 and a dispersion ratio of 2421.0 was used.

Further, as the sensor of the above-described sensing surface 400, a 34 μm sensor of 80 × 80 pixels can be used.

With the long wavelength infrared camera 1000 of the present invention having the 21 degree horizontal viewing angle of the above structure, the experimental results of Figs. 3 to 8 can be obtained.

3 is a light trace analysis diagram of a long wavelength infrared camera having a 21 degree horizontal viewing angle of the present invention. 4 is a graph showing longitudinal spherical aberration of a long wavelength infrared camera having a 21 degree horizontal viewing angle of the present invention. Fig. 5 is an aberration analysis diagram relating to astigmatism of a long-wavelength infrared camera having a 21 degree horizontal viewing angle of the present invention. Fig. 6 is a graph showing distortion aberration of a long-wavelength infrared camera having a 21 degree horizontal viewing angle of the present invention. Fig. 7 is a graph showing a modulation transfer function showing the resolution of a long-wavelength infrared camera having a 21 degree horizontal viewing angle of the present invention. Fig. 8 is a view showing a spot diagram of a long wavelength infrared camera having a 21 degree horizontal viewing angle of the present invention.

As shown in FIGS. 3 to 8, the long-wavelength infrared camera having a 21-degree horizontal viewing angle of the present invention has a phase value adjacent to the central axis in almost all fields, and thus not only indicates that the calibration states of various aberrations are good, but also Indicates that the modulation transfer function (optical demand performance/resolution) is satisfied.

Further, the peripheral light ratio of the optical system of the present invention can be ensured to be 95% or more, and the distortion rate can be limited to 5% or more, whereby a more vivid image can be obtained.

Therefore, the optical material for molding such as non-oxide infrared optical glass can be sufficiently applied, so that the production cost can be reduced as compared with the conventional xenon lens, and it can be easily applied to the civilian field through mass production.

Claims (5)

A lens having a 21 degree horizontal viewing angle formed by molding an optical material, comprising: a concave surface (R2) for first refracting light incident from a subject; and a convex surface (R3), For the second refraction of the light passing through the concave surface (R2), the concave surface (R2) and the convex surface (R3) are determined according to the relationship of the following formula 1, Table 1 and Table 2: Where k is the conic surface coefficient, A4, A6, A8, and A10 are aspherical coefficients, h is the distance from the optical axis to the concave or convex surface, and c is the central curvature. Among them, the radius of curvature and the surface thickness have a tolerance of ±0.5%, (the diameter of the concave surface (R2)) / (the diameter of the convex surface (R3)) is 0.57 (±0.5% tolerance). A lens having a 21 degree horizontal viewing angle as claimed in claim 1, wherein the lens is formed with an edge portion extending from the concave surface (R2) and the convex surface (R3) in a direction perpendicular to the optical axis. A lens having a 21 degree horizontal viewing angle as claimed in claim 2, wherein (the average of the central portion thickness (TC)/diameter of the concave surface (R2) and the convex surface (R3)) is 0.79 (±0.5% tolerance), (Thickness of edge portion of lens) / (Center portion thickness (TC) of concave surface (R2) and convex surface (R3)) was 0.74 (±0.5% tolerance). A long-wavelength infrared camera having a 21 degree horizontal viewing angle, comprising: an aperture; the lens according to any one of claims 1 to 3; an infrared filter disposed apart from the convex surface (R3); and sensing The subject is imaged by light passing through the above-described infrared filter. A long-wavelength infrared camera having a 21 degree horizontal viewing angle according to claim 4, wherein a distance between the aperture and the concave surface (R2) is 0.7 mm ± 0.5%, and a central portion of the concave surface (R2) and the convex surface (R3) The thickness (TC) is 6.295 mm ± 0.5%, the distance from the convex surface (R3) to the infrared filter is 6.7 mm ± 0.5%, and the thickness of the above infrared filter is 0.65 mm ± 0.5%, from the above infrared filtering The distance from the device to the sensing surface was 1.3 mm ± 0.5%, and the refractive index of the above filter was 3.421, and the dispersion ratio was 2421.0.