TWI663441B - Long-wavelength infrared camera with 54 degree angle of view and lens for the camera - Google Patents

Abstract

The present invention relates to a long-wavelength infrared camera and a camera lens with a horizontal viewing angle of 54 degrees, which are formed of optical materials for molding, and include a concave surface (R2) for performing first light incident from a subject. Secondary refraction; and convex surface (R3) for refraction of light passing through the concave surface (R2), the concave surface (R2) and convex surface (R3) are based on the relationship of the following formula 1, table 1 and table 2. set:

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

Among them, the curvature radius and the surface thickness have a tolerance of ± 0.5%, and (the diameter of the concave surface (R2)) / (the diameter of the convex surface (R3)) is 0.46 (tolerance of ± 0.5%).

Description

   Long-wavelength infrared camera with 54-degree horizontal viewing angle and camera lens   

The present invention relates to a long-wavelength infrared camera and a lens for a camera having a horizontal viewing angle of 54 degrees, and more particularly, to a universal long-wavelength infrared (also known as "LWIR") camera and a lens for a camera that can be used in various fields such as fire monitoring.

Long-wavelength infrared is light with a wavelength of 8 μm to 12 μm, including the wavelength range of infrared rays released by humans.

A long-wavelength infrared camera is a camera that can image by detecting infrared rays emitted by humans or animals at night.

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

Therefore, the infrared energy released from humans or animals by a long-wavelength infrared camera can be used to determine the presence of humans or animals and obtain images.

However, in the case of South Korea, the development of long-wavelength infrared-only lenses and long-wavelength infrared camera systems has been extremely slow, so the actual situation is that most of them rely on imports and sell at high prices.

In particular, conventional infrared cameras are mainly manufactured by using a germanium (Germanium) lens-based straight-processed lens. Therefore, the manufacturing cost is high and the manufacturing time is long.

Therefore, germanium lenses are mainly used in the military field, and are rarely used in the civilian field due to price issues.

In particular, in the case of a wide-angle lens suitable for a fire monitoring device, it needs to be in the shape of a small body, but it is actually difficult to directly process it, so a molded lens is required.

    [Prior technical literature]         [Patent Literature]    

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

The present invention has been made in order to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide an optical material suitable for molding. Therefore, compared with a conventional germanium lens, the production cost can be reduced, and mass production can be achieved. It is simple and suitable for the civilian field of long-wavelength infrared cameras with 54-degree horizontal viewing angles and camera lenses.

In addition, an object of the present invention is to provide a refractive index and a lens transmission characteristic which are improved compared with conventional optical devices made of germanium materials, and it can constitute a variety of optical systems from ultra-small-aperture lenses to medium-aperture lenses, and is applicable to fire Monitored long-wavelength infrared cameras with 54-degree horizontal viewing angles and camera lenses.

In order to achieve the above object, the lens for a long-wavelength infrared camera having a horizontal viewing angle of 54 degrees according to the present invention is a lens having a horizontal viewing angle of 54 degrees, that is, it is formed by molding an optical material including: concave surface R2, For first refraction of light incident from the subject; and convex surface R3 for second refraction of light passing through the concave surface R2, the concave surface R2 and convex surface R3 according to the following formula 1, table 1 and table Depending on the relationship between 2:

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

Among them, the curvature radius and the surface thickness have a tolerance of ± 0.5%, and (the diameter of the concave surface R2) / (the diameter of the convex surface R3) is 0.46 (tolerance of ± 0.5%).

The invention is characterized in that the lens is formed with an edge portion extending from between 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 thickness TC / diameter of the center portions of the concave surface R2 and the convex surface R3) is 0.86 (± 0.5% tolerance), (thickness of the edge portion of the lens) / (the center of the concave surface R2 and the convex surface R3) Part thickness TC) is 0.60 (tolerance of ± 0.5%).

In addition, the long-wavelength infrared camera with a horizontal viewing angle of 54 degrees according to the present invention includes: an aperture; the lens; an infrared filter, which is spaced from the convex surface R3; and a sensing surface, which passes through the infrared filter. Light from the camera to image the subject.

The present invention is characterized in that the distance between the aperture and the concave surface R2 is 0.36 mm ± 0.5%, the thickness of the central portion TC of the concave surface R2 and the convex surface R3 is 3.305 mm ± 0.5%, and from the convex surface R3 to the infrared filter The distance is 2.0mm ± 0.5%, the thickness of the infrared filter is 0.65mm ± 0.5%, the distance from the infrared filter to the sensing surface is 1.3mm ± 0.5%, and the refractive index of the filter is 3.421 The dispersion ratio was 2421.0.

According to the present invention configured as described above, as a popular optical system applicable to the field of fire monitoring and detection, it is possible to detect a living thing or a thing with only one lens, and it is applicable to the inside and outside of a building and a specific device (inside a transformer). Etc.) or narrow spaces.

In addition, according to the present invention, it has a structure that can be molded by molding, which facilitates manufacturing and mass production, and also has the advantage of low manufacturing cost.

100‧‧‧ aperture

200‧‧‧ lens

210‧‧‧Edge

300‧‧‧ Infrared Filter

400‧‧‧Sensing surface

1000‧‧‧ Long-wavelength infrared camera with 54-degree horizontal viewing angle

R2‧‧‧concave

R3‧‧‧ convex

1 (a) and 1 (b) are perspective views of a long-wavelength infrared camera with a horizontal viewing angle of 54 degrees according to the present invention.

FIG. 2 is a configuration diagram showing a configuration of the optical system of FIG. 1.

3 is a light tracking analysis diagram of a long-wavelength infrared camera with a horizontal viewing angle of 54 degrees according to the present invention.

FIG. 4 is a graph showing a longitudinal spherical aberration of a long-wavelength infrared camera with a horizontal viewing angle of 54 degrees according to the present invention.

5 is an aberration analysis diagram related to astigmatism of a long-wavelength infrared camera with a horizontal viewing angle of 54 degrees according to the present invention.

FIG. 6 is a graph showing distortion of a long-wavelength infrared camera with a horizontal viewing angle of 54 degrees according to the present invention.

FIG. 7 is a graph analyzing a modulation transfer function (MTF) showing the resolution of a long-wavelength infrared camera with a horizontal viewing angle of 54 degrees according to the present invention.

8 is a diagram showing a spot diagram of a long-wavelength infrared camera having a horizontal viewing angle of 54 degrees according to the present invention.

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

As shown in FIGS. 1 and 2, the long-wavelength infrared camera 1000 with a horizontal viewing angle of 54 degrees according to the present invention includes: an aperture 100; a lens 200 including a concave surface R2 and a convex surface R3. The concave surface R2 is used to The light is refracted for the first time, and the convex surface R3 is used for the second refraction of the light passing through the concave surface R2; the infrared filter 300 is disposed apart from the convex surface R3; and the sensing surface 400 passes through the infrared rays. The light of the filter 300 forms a subject.

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

The above-mentioned lens 200 having a horizontal viewing angle of 54 degrees is formed of an optical material for molding.

Optical materials for molding are made of glass or plastic. Compared with similar materials that have been sold in the past, materials with high refractive index and lens transmission characteristics are used. Materials for various optical systems to medium-caliber lenses.

For example, as the lens material suitable for the optical system design of the present invention, a material having a refractive index of 2.5 or more and a high transmittance of 65% or more in a wavelength band up to 12 μm can be used.

If the optical system is constituted by the optical material of the present invention, a clearer image can be expressed than in the past, and molding by molding can be performed, thereby making it possible to construct a safety monitoring universal long-wavelength infrared with simple manufacturing and low manufacturing cost. Camera optical system.

In addition, the long-wavelength infrared camera 1000 having a horizontal viewing angle of 54 degrees according to the present invention performs an optical design of one set of one popular type of long-wavelength infrared ray to which 6400 pixels (sensors) are applied.

The optical system of the present invention increases the thickness of the lens central portion and the edge portion 210 so as to be in a form that is favorable for molding.

The present invention, as an optical system for a long-wavelength infrared camera for fire monitoring, includes a concave surface R2 facing the object and a convex surface R3 on the opposite side, which have a positive (+) refractive index as a whole, and both surfaces are aspheric surfaces.

In addition, the above-mentioned concave surface R2 and convex surface R3 of the lens 200 of the present invention are determined based on the relationship of the following formula 1.

Among them, k is a conic coefficient, A4, A6, A8, and A10 are aspheric coefficients, h is a distance from the optical axis to a concave or convex surface, and c is a center curvature.

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

And, 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 dispersion ratio v1 is determined by the following formula.

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

Among them, n110 is the refractive index of a lens with a wavelength of 10 μm, n108 is the refractive index of a lens with a wavelength of 8.0 μm, n112 is the refractive index of a lens with a wavelength of 12 μm, 2.0 <n110 <3.0

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

In particular, the value of (thickness of the central portion of the concave surface R2 and the convex surface R3 TC / the average value of the diameter of the concave surface R2 and the diameter of the convex surface R3) is 0.86 (tolerance of ± 0.5%), (thickness of the edge portion of the lens) / (the concave surface described above) The value of the thickness TC at the center portion of R2 and convex surface R3 is 0.60 (tolerance of ± 0.5%), and therefore, the viewing angle of 54 degrees can be accurately adjusted.

In addition, since the thickness of the center portion and the edge portion of the lens is thick, it can take a shape that is favorable for molding.

According to the present invention, the distance between the diaphragm and the concave surface R2 can be set to 0.36 mm ± 0.5%, and the thickness TC of the central portion of the concave surface R2 and the convex surface R3 can be set to 3.305 mm ± 0.5%. From the convex surface R3 to the infrared filter, The distance of the optical filter is set to 2.0 mm ± 0.5%, the thickness of the infrared filter is set to 0.65 mm ± 0.5%, and the distance from the infrared filter to the sensing surface is set to 1.3 mm ± 0.5%.

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

In addition, the edge portion of the lens 200 is manufactured in an arc shape, which can facilitate assembly and manufacturing of the optical system.

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

Through 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 a modulation transfer function value representing a resolution.

An exemplary embodiment of the long-wavelength infrared camera 1000 having a horizontal viewing angle of 54 degrees according to the present invention is described based on the structure described above.

First, a long-wavelength infrared camera having a horizontal viewing angle of 54 degrees is used as a long-wavelength infrared camera optical system suitable for fire monitoring and the like. By applying a non-oxide infrared optical glass formed of Ge _27.5 -Sb _13.5 -Se ₆₀ For molding.

In addition, the curvature radii of the concave surface R2 and convex surface R3 of the lens 200 are set to -7.0622mm (aspherical), -3.4640mm (aspherical), the diameter of the concave surface R2 is set to 2.42mm, and the diameter of the convex surface R3 is set to 5.24. mm.

The entire lens 200 forms a thickness of 3.64 mm.

For mounting, an edge portion 210 extending from the concave surface R2 and the convex surface R3 in a direction perpendicular to the optical axis is formed. When the edge portion 210 is considered, the diameter of the entire lens is set to 7.50 mm.

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

An arc-shaped portion having a radius of curvature 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-mentioned Formula 1 and Tables 1 and 2.

Further, the thickness TC of the central portion of the concave surface R2 and the convex surface R3 was set to 3.305 mm, and the thickness of the edge portion of the lens was set to 1.97.

In addition, the distance between the diaphragm 100 and the concave surface R2 is set to 0.36 mm, the distance from the convex surface R3 to the infrared filter 300 is set to 2.0 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 is set to 1.3 mm.

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

In addition, as the sensor of the sensing surface 400, a 34 μm sensor of 80 × 80 pixels can be used.

For the long-wavelength infrared camera 1000 of the present invention having a horizontal viewing angle of 54 degrees, the experimental results of FIGS. 3 to 8 can be obtained.

3 is a light tracking analysis diagram of a long-wavelength infrared camera with a horizontal viewing angle of 54 degrees according to the present invention. 4 is a graph showing a longitudinal spherical aberration of a long-wavelength infrared camera having a horizontal viewing angle of 54 degrees according to the present invention. FIG. 5 is an aberration analysis diagram related to astigmatism of a long-wavelength infrared camera with a horizontal viewing angle of 54 degrees according to the present invention. FIG. 6 is a graph showing distortion aberrations of a long-wavelength infrared camera with a horizontal viewing angle of 54 degrees according to the present invention. FIG. 7 is a graph analyzing a modulation transfer function showing a resolution of a long-wavelength infrared camera having a horizontal viewing angle of 54 degrees according to the present invention. 8 is a diagram showing a spot diagram of a long-wavelength infrared camera having a horizontal viewing angle of 54 degrees according to the present invention.

As shown in FIG. 3 to FIG. 8, the long-wavelength infrared camera with a horizontal viewing angle of 54 degrees in the present invention has phase values adjacent to the central axis in almost all fields, so it not only indicates that the calibration status of various aberrations is good, but also Denotes that the modulation transfer function (optical performance / resolution) is satisfied.

In addition, the lens material of the present invention, as a molding material, has a high refractive index and a high transmittance of 65% or more in a wavelength band as high as 12 μm compared with a material suitable for a conventional market.

The optical system of the present invention is designed to be suitable for a group of 6400 pixels with a long-wavelength infrared light for fire monitoring. The optical system of the present invention has a shape that is favorable for molding by increasing the thickness of the central part and the edge part of the lens.

In addition, the optical system has a peripheral brightness ratio of 84% or more and a distortion rate of 20% or less, thereby ensuring optical system performance.

Therefore, it can be fully applied to molding optical materials such as non-oxide infrared optical glass. Therefore, compared with the conventional germanium lens, the production cost can be reduced, and it can be easily applied to the civilian field through mass production.

Claims (5)

A lens with a horizontal viewing angle of 54 degrees, which is formed of a molded optical material and includes: a concave surface (R2) for first refraction of light incident from a subject; and a convex surface (R3), The second refraction is performed on the light passing through the concave surface (R2), and the concave surface (R2) and convex surface (R3) are determined according to the relationship of the following formula 1, Table 1, and Table 2: Where k is the conic coefficient, A4, A6, A8, and A10 are aspheric coefficients, h is the distance from the optical axis to the concave or convex surface, and c is the center curvature. Among them, the curvature radius and the surface thickness have a tolerance of ± 0.5%, and (the diameter of the concave surface (R2)) / (the diameter of the convex surface (R3)) is 0.46 (tolerance of ± 0.5%). According to claim 1, the lens having a horizontal viewing angle of 54 degrees, wherein the lens is formed with an edge portion extending from between the concave surface (R2) and the convex surface (R3) in a direction perpendicular to the optical axis. For example, a lens having a 54-degree horizontal viewing angle as claimed in item 2, where (the average of the thickness of the center portion (TC) of the concave surface (R2) and the convex surface (R3) / the diameter of the concave surface (R2) and the diameter of the convex surface (R3)) It is 0.86 (tolerance of ± 0.5%), (thickness of the edge of the lens) / (thickness of the central portion (TC) of the concave (R2) and convex (R3)) is 0.60 (tolerance of ± 0.5%). A long-wavelength infrared camera with a horizontal viewing angle of 54 degrees, comprising: an aperture; the lens according to any one of claims 1 to 3; an infrared filter, which is arranged apart from the convex surface (R3); and a sensor And imaging a subject by light passing through the infrared filter. For example, a long-wavelength infrared camera with a horizontal viewing angle of 54 degrees as claimed in claim 4, wherein the distance between the aperture and the concave surface (R2) is 0.36mm ± 0.5%, and the central portions of the concave surface (R2) and convex surface (R3) The thickness (TC) is 3.305mm ± 0.5%, the distance from the convex surface (R3) to the infrared filter is 2.0mm ± 0.5%, and the thickness of the infrared filter is 0.65mm ± 0.5%. The distance from the sensor to the sensing surface is 1.3 mm ± 0.5%. The refractive index of the infrared filter is 3.421 and the dispersion ratio is 2421.0.