KR101554130B1

KR101554130B1 - Long wavelength infrared optical system with wide field of view

Info

Publication number: KR101554130B1
Application number: KR1020150048835A
Authority: KR
Inventors: 김현규
Original assignee: (주)토핀스
Priority date: 2014-05-27
Filing date: 2015-04-07
Publication date: 2015-09-21
Also published as: WO2016163707A1

Abstract

The present invention relates to a far infrared optical system with high resolution and a wide field of view, which comprises multiple lenses. Each lens is characterized by forming a non-spheric surface and minimizing an image distortion. At that time, two or more lenses among the lenses further form a diffraction pattern to minimize changes in a focusing distance at -40-60°C.

Description

[0001] LONG WAVELENGTH INFRARED OPTICAL SYSTEM WITH WIDE FIELD OF VIEW [0002]

The present invention relates to a high resolution wide viewing angle far infrared ray optical system, and more particularly, to a high resolution wide viewing angle far infrared ray optical system which minimizes image distortion and variation of focal distance within a temperature range of -40 ° C to 60 ° C.

The far-infrared ray includes a wavelength band of infrared rays emitted by humans as light having a wavelength range of 8 to 13 m. A far infrared ray camera is a camera that can detect an infrared ray generated by a person or an object at night and pick up the image.

The body temperature of a human or an animal is about 310K, and the peak wavelength of black-body radiation at 310K is about 8 to 13 mu m. Therefore, if a far-infrared ray emitted by a human being or an object is captured by a far-infrared camera, the presence thereof can be known.

A related prior art is Korean Patent Registration No. 10-1214601 entitled "Non-thermal infrared lens module ". Since the prior art is an optical system having two or more lenses and the lenses are made of either selenide zinc (ZnSe) or germanium (Ge), a structure in which a lens made of selenized zinc and a lens made of germanium are arranged And the focal distance is minimized over a wide temperature range due to the structure in which a lens made of selenium zinc and a lens made of germanium are arranged.

Korean Patent Registration No. 10-1214601 entitled "Nonthermalized Infrared Lens Module"

An object of the present invention is to provide a high resolution wide viewing angle far infrared ray optical system capable of minimizing image distortion.

Another object of the present invention is to provide a high-resolution wide viewing angle far-infrared optical system capable of minimizing a change in focal distance within a temperature range of -40 ° C to 60 ° C.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not intended to limit the invention to the particular embodiments that are described. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, There will be.

According to an aspect of the present invention, there is provided an image forming apparatus including a plurality of lenses, each lens forming an aspherical surface to minimize image distortion.

Specifically, two or more of the lenses may further form a diffraction pattern to minimize a change in focal distance within a temperature range of -40 ° C to 60 ° C.

The diffraction pattern may be formed on the aspherical surface.

The lenses having the aspherical surface may be arranged in a line from the object, and the lenses having the aspheric surface and the diffraction pattern may be arranged in a line after the lenses having the aspherical surface.

Among the lenses, the lens facing the object may be made of germanium, and the remaining lenses may be made of selenide zinc.

According to the present invention, the image distortion can be minimized by forming the aspherical surfaces of the lenses, and the change of the focal length can be minimized within a temperature range of -40 DEG C to 60 DEG C by forming two or more lenses of the lenses further in the diffraction pattern .

1 is a view showing a high resolution wide viewing angle far infrared ray optical system of the present invention.
FIG. 2 shows LSA (Longitudinal Spiral Absorber), astigmatic field curvature, and distortion for the distance from the object to infinity, respectively.
3 shows ray aberration with respect to an object at a distance of infinity.
4 shows LSA (Longitudinal Spatial Aberration), astigmatic field curvature, and distortion with respect to an object at a distance of 5 m, respectively.
5 shows the ray aberration with respect to an object at a distance of 5 m.
Fig. 6 shows the MTF for an object at infinity.
Figure 7 shows the MTF for a distance of 5 m to an object.
Fig. 8 shows through focus MTFs at -35 캜, 20 캜 and 55 캜, respectively, with respect to the distance from the object to Infinity.
FIG. 9 shows through-focus MTFs (th? Rough focus MTF) at -35 占 폚, 20 占 폚, and 55 占 폚, respectively, with respect to a distance of 5 m.
Fig. 10 shows the relative illumination at -35 deg. C, 20 deg. C and 55 deg. C, respectively, with respect to the distance from the object to Infinity.
FIG. 9 shows the relative illumination at -35 ° C, 20 ° C and 55 ° C relative to the object, respectively, at a distance of 5 m.
FIG. 11 shows a defocus for an infinite distance to an object.
Fig. 12 shows a defocus for a distance of 5 m to an object.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same components are denoted by the same reference symbols whenever possible. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail.

As shown in Fig. 1, the high resolution wide viewing angle far infrared ray optical system (hereinafter referred to as "the optical system of the present invention") of the present invention comprises a plurality of lenses. For example, the optical system of the present invention may be composed of four lenses (L1 to L4), and the first lens (L1), the second lens (L2), the third lens (L3) And the fourth lens L4 are arranged in order.

The first lens L1 is a lens in which a convex surface having a positive refractive power is formed on the object-side surface and a concave surface having a negative refractive power is formed on the rear surface, and a negative magnification is formed on the entire surface.

The second lens (L2) disposed behind the first lens (L1) also forms a convex surface having a positive refractive power on the object-side surface and a concave surface having a negative refractive power on the object-side surface, and forms a negative magnification It is one lens.

The third lens L3 disposed behind the second lens L2 forms a concave surface having a negative refractive power on the object side front surface and a convex surface having a positive refractive power on the rear surface and forms a positive magnification as a whole It is one lens.

The fourth lens L4 disposed at the rear of the third lens L3 has a concave surface having negative refracting power on the object-side surface and a convex surface having positive refracting power on the object-side surface and forms a positive magnification as a whole It is one lens.

The infrared ray transmitted sequentially through the first lens L1, the second lens L2, the third lens L3 and the fourth lens L4 passes through the detector window W, And forms an image of the object on the light receiving surface.

In the optical system according to the present invention, each of the lenses L1 to L4 has an aspheric surface S. Preferably, the aspherical surface S is formed on the convex surface having a positive refractive power in each of the lenses L1 to L4. That is, the convex surface having a positive refractive power in each of the lenses L1 to L4 is an aspherical surface (S).

The front surface of the first lens L1 having a positive refractive power is formed as an aspherical surface S and the front surface of the second lens L2 having a positive refractive power is formed as an aspherical surface S, The back surface having a positive refractive power is formed as an aspherical surface S and the rear lens L4 having a positive refractive power is formed as an aspherical surface S. [

In this configuration, a diffraction pattern (not shown) is further formed on two or more of the lenses. For example, the diffraction pattern is preferably formed on the third lens L3 and the fourth lens L4. At this time, the diffraction pattern is formed on the aspherical surface S of the third lens L3 and the fourth lens L4. That is, the diffraction pattern is formed on the aspherical surface S of the third lens L3 and the fourth lens L4 having a positive refractive power. The diffraction pattern may be formed in various shapes on the aspherical surfaces of the third lens L3 and the fourth lens L4, and may be formed in, for example, a concentric circle shape.

In the optical system of the present invention as described above, the image distortion is minimized by forming the convex surface having the positive refracting power on the aspheric surface S of the four lenses L1 to L4, and more than two of the lenses L1 to L4 By further forming the diffraction pattern on the aspheric surface S of the lenses L3 and L4, the change of the focal distance is minimized within the temperature range of -40 deg. C to 60 deg.

In this case, the optical system of the present invention has the lens L1 facing the object and the remaining lenses L2, L3 and L4 made of zinc selenide (ZnSe) To minimize the variation of the focal length within the temperature range of < RTI ID = 0.0 > 60 C < / RTI >

As an example of the optical system of the present invention, the spectral range may be 7.7 to 12.8 mu m, the effective focal length may be 6.25 mm, the F number may preferably be 1.2, May be from 5 mm to Infinity (fixed focus), and the instantaneous field of view may be 2.236 mrad.

At this time, if the F number is less than or greater than 1.2, the lenses L1 to L4 must be arranged or arranged in close proximity to each other, so that it is difficult to minimize the image distortion and the variation of the focal distance within the temperature range of 40 to 60 占 폚.

FIG. 2 shows LSA (Longitudinal Spiral Absorber), astigmatic field curvature, and distortion for the distance from the object to infinity, respectively.

FIG. 3 shows the ray aberration with respect to the object infinity, FIG. 4 shows the ray aberration with respect to the object, and FIG. 4 shows the ray aberration with respect to the object when the distance from the object is LSA (Longitudinal Lateral Spur) astigmatic field curvature, and distortion, respectively.

FIG. 5 shows the ray aberration with respect to an object at a distance of 5 m, FIG. 6 shows an MTF with respect to an object at infinity, and FIG. 7 shows an MTF at an object with a distance of 5 m .

Fig. 8 shows through-focus MTFs at -35 DEG C, 20 DEG C, and 55 DEG C, respectively, with respect to the distance to an object. Fig. 9 is a graph showing the through- 20 ° C, and 55 ° C, respectively.

FIG. 10 shows the relative illumination at -35 ° C, 20 ° C and 55 ° C, respectively, with respect to the distance to the object, and FIG. 9 shows the relative illumination at -35 ° C , 20 ° C, and 55 ° C, respectively.

Fig. 11 shows a defocus for an object at infinity, and Fig. 12 shows a defocus for an object at a distance of 5 m.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention as defined by the appended claims. It will be possible. The scope of the present invention is defined by the appended claims, and all differences within the scope of the claims are to be construed as being included in the present invention.

L1: first lens
L2: second lens
L3: Third lens
L4: fourth lens
S: Aspherical surface
W: detector window

Claims

Comprising a plurality of lenses,
Each of the lenses forms an aspherical surface to minimize image distortion,
Two or more of the lenses further form a diffraction pattern to minimize the variation of the focal distance within a temperature range of -40 DEG C to 60 DEG C,
Wherein the lens having the aspherical surface is arranged in a line from an object, and the lenses having the aspheric surface and the diffraction pattern are arranged in a line after the lenses having the aspheric surface.

delete

The method according to claim 1,
And the diffraction pattern is formed on the aspherical surface.

delete

The method according to claim 1,
Wherein the lens of the lenses is made of germanium material and the other lenses are made of selenide zinc material.