A small-F-number, double-diaphragm, double-view-field, uncooled long-wave infrared optical system

Abstract

The application discloses a kind of small F number, double diaphragm, double field of view, non-refrigeration long-wave infrared optical system, including first lens, second lens, third lens, fourth lens, fifth lens and non-refrigeration long-wave infrared detector protection window;First lens has positive focal power, its front surface is spherical surface, rear surface is even aspheric surface;Second lens has negative focal power, its front surface is binary diffraction surface with even aspheric surface as base, rear surface is spherical surface;Third lens has positive focal power, its front surface is spherical surface, rear surface is even aspheric surface;Fourth lens has positive focal power, its front surface is spherical surface, rear surface is even aspheric surface;Fifth lens has positive focal power, its front surface is spherical surface, rear surface is even aspheric surface;Second lens is moved forward and backward along optical axis direction to realize the zoom of big field of view, small field of view.This optical system has big, small two fields of view, and the F number corresponding to big, small field of view is relatively small, can realize the design requirement of miniaturization, light weight.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of optical design, and relates to a small-F-number, double-diaphragm, double-view-field, non-cooled long-wave infrared optical system. BACKGROUND

[0002] At present, photoelectric search and aiming equipment not only needs a large search field of view, but also needs a longer target recognition capability, which gives birth to a double-view-field variable optical system, wherein a large field of view is used for target search, and a small field of view is used for target recognition. For a double-view-field non-cooled long-wave infrared optical system, the larger the effective aperture is, the smaller the F number is, the stronger the target energy collection capability is, and the farther the observed target distance is. The double-view-field non-cooled long-wave infrared optical system adopts a design type of large and small field of view sharing a diaphragm, which will increase the volume and weight of the optical system without increasing the effective light aperture, which is not conducive to the light weight and miniaturization of photoelectric equipment. SUMMARY

[0003] The application aims to overcome the above-mentioned deficiencies, and provides a small-F-number, double-diaphragm, double-view-field, non-cooled long-wave infrared optical system according to the technical problem to be solved.

[0004] To achieve the above-mentioned purpose, the application adopts the following technical scheme:

[0005] According to an embodiment of the small-F-number, double-diaphragm, double-view-field, non-cooled long-wave infrared optical system, from the object side to the image side, along the optical axis direction, the optical axis comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens and a non-cooled long-wave infrared detector protection window in sequence.

[0006] According to an embodiment of the small-F-number, double-diaphragm, double-view-field, non-cooled long-wave infrared optical system, wherein the optical system is adapted to a non-cooled long-wave infrared detector 640x512, a detector of 12 microns or below.

[0007] According to an embodiment of the small-F-number, double-diaphragm, double-view-field, non-cooled long-wave infrared optical system, wherein the effective focal length of the small field of view optical system is 132 mm, the F number is 0.9, the linear field of view is 9.84 mm, the maximum distortion is 0.5%, and the diaphragm plane is selected on the front surface of the first lens.

[0008] According to an embodiment of the small-F-number, double-diaphragm, double-view-field, non-cooled long-wave infrared optical system, wherein the effective focal length of the large field of view optical system is 66 mm, the F number is 0.75, the linear field of view is 9.84 mm, the maximum distortion is-0.2%, and the diaphragm plane is selected on the front surface of the third lens.

[0009] According to one embodiment of the small F number, double diaphragm, double field of view, non-refrigeration long wave infrared optical system of the present application, the working wave band of the optical system is 8-10-12 μm (central wave length), and the total optical length is 186 mm.

[0010] According to one embodiment of the small F number, double diaphragm, double field of view, non-refrigeration long wave infrared optical system of the present application, the first lens, the second lens, the third lens and the fifth lens of the optical system are made of germanium material, and the fourth lens is made of IRG206 material.

[0011] According to one embodiment of the small F number, double diaphragm, double field of view, non-refrigeration long wave infrared optical system of the present application, the first lens has positive focal power, the front surface is spherical, and the rear surface is even aspheric surface; the second lens has negative focal power, the front surface is binary diffractive surface with even aspheric base, and the rear surface is spherical; the third lens has positive focal power, the front surface is spherical, and the rear surface is even aspheric surface; the fourth lens has positive focal power, the front surface is spherical, and the rear surface is even aspheric surface; the fifth lens has positive focal power, the front surface is spherical, and the rear surface is even aspheric surface; and the non-refrigeration long wave infrared detector protection window is a flat glass, and the front surface and the rear surface have infinite radius.

[0012] According to one embodiment of the small F number, double diaphragm, double field of view, non-refrigeration long wave infrared optical system of the present application, the second lens of the optical system is moved forward and backward along the optical axis direction to realize the zooming of the large and small fields of view.

[0013] According to one embodiment of the small F number, double diaphragm, double field of view, non-refrigeration long wave infrared optical system of the present application, the even aspheric surface of the lens satisfies the following expression:

[0014]

[0015] Wherein z represents the height of the even aspheric surface along the optical axis direction, c represents the curvature of the surface vertex, k represents the conic coefficient, α4, α6, α8, α 10 represents the high-order aspheric coefficient.

[0016] According to one embodiment of the small F number, double diaphragm, double field of view, non-refrigeration long wave infrared optical system of the present application, the binary diffractive surface satisfies the following expression.

[0017] φ=A1ρ 2 +A2ρ 4

[0018] Wherein Φ is the phase of the diffractive surface, ρ=r / r n n ​is the planned radius of the diffraction surface, and A1 and A2 are the phase coefficients of the diffraction surface.

[0019] Beneficial effects of the present invention:

[0020] The small F-number, double-aperture, double-field-of-view, uncooled long-wave infrared optical system of the present invention has two fields of view, large and small, which correspond to different aperture positions and F-numbers. The effective focal length of the small field of view of this optical system is 132mm, the F-number is 0.9, the line field of view is 9.84mm, the maximum distortion is 0.5%, and the aperture surface is selected on the front surface of the first lens to improve the ability to identify targets in a small field of view. The effective focal length of the large field of view is 66mm, the F-number is 0.75, the line field of view is 9.84mm, the maximum distortion is -0.2%, and the aperture surface is selected on the front surface of the third lens, which has a larger field of view of the search target and improves the ability to search for targets in a large field of view. The design of the double apex can realize the miniaturization and lightweight design of the optical system. The specific invention has the following advantages:

[0021] 1) The large and small fields of view of this optical system correspond to different aperture positions;

[0022] 2) The F-numbers corresponding to both large and small fields of view of this optical system are relatively small;

[0023] 3) This optical system has high resolution for large and small fields of view;

[0024] 4) This optical system can achieve miniaturization and lightweight design requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 : Optical layout diagram of the present invention.

[0026] Figure 2 : Layout diagram of large and small field of view of the optical system.

[0027] Figure 3 : Small field MTF curve of optical system.

[0028] Figure 4 : Small field of view point diagram of optical system.

[0029] Figure 5 : Distortion curve of optical system with small field of view.

[0030] Figure 6 : MTF curve of optical system with large field of view.

[0031] Figure 7 : Spot diagram of optical system with large field of view.

[0032] Figure 8 : Distortion curve of optical system with large field of view. DETAILED DESCRIPTION

[0033] In order to make the purposes, contents and advantages of the present application more clear, the specific embodiments of the present application are described in further detail below in combination with the drawings and examples.

[0034] Referring to Figure 1 As shown in the drawings, a small F number, double diaphragm, double field of view, non-cooled long-wave infrared optical system, from the object side to the image side, along the optical axis direction, in turn includes a first lens 1, a second lens 2, a third lens 3, a fourth lens 4, a fifth lens 5 and a non-cooled long-wave infrared detector protection window 6.

[0035] The optical system is adapted to a non-cooled long-wave infrared detector 640x512, 12 microns and below.

[0036] The optical system has a small field of view effective focal length of 132mm, an F number of 0.9, a line field of view of 9.84mm, a maximum distortion of 0.5%, and a diaphragm plane selected on the front surface S11 of the first lens 1.

[0037] The optical system has a large field of view effective focal length of 66mm, an F number of 0.75, a line field of view of 9.84mm, a maximum distortion of -0.2%, and a diaphragm plane selected on the front surface S31 of the third lens 3.

[0038] The optical system has a working waveband of 8μm~10μm (center wavelength)~12μm, and an optical total length of 186mm.

[0039] The first lens 1, the second lens 2, the third lens 3 and the fifth lens 5 of the optical system are made of germanium material, and the fourth lens 4 is made of IRG206 material.

[0040] The first lens 1 has positive refractive power, the front surface S11 is a spherical surface, and the rear surface S12 is an even aspheric surface.

[0041] The second lens 2 has negative refractive power, the front surface S21 is a binary diffractive surface with an even aspheric base, and the rear surface S22 is a spherical surface.

[0042] The third lens 3 has positive refractive power, the front surface S31 is a spherical surface, and the rear surface S32 is an even aspheric surface.

[0043] The fourth lens 4 has positive refractive power, the front surface S41 is a spherical surface, and the rear surface S42 is an even aspheric surface.

[0044] The fifth lens 5 has positive refractive power, the front surface S51 is a spherical surface, and the rear surface S52 is an even aspheric surface.

[0045] The non-cooled long-wave infrared detector protection window 6 is a flat glass, and the front surface S61 and the rear surface S62 have infinite radii.

[0046] The second lens 2 moves forward and backward along the optical axis direction to realize zooming of large and small fields, and the total moving amount is 16.95mm.

[0047] The front surface S11 of the first lens 1 is exposed to the outside, and needs to be coated with a carbon film to play a protective role, and the rest of the surfaces are coated with an anti-reflection film.

[0048] Table 1 is the optical structure parameters of the optical system of the present application.

[0049] Table 1

[0050]

[0051] The even-order aspherical surface type involved in the S12, S21, S32, S42 and S52 surfaces satisfies the following expression.

[0052]

[0053] Where z represents the sag of the even-order aspherical surface along the optical axis direction at a height of r, c represents the curvature of the surface vertex, k represents the conic coefficient, and a4, a6, a8, a 10 represents the high-order aspherical coefficient.

[0054] Table 2 is the even-order aspherical surface parameters of the S12, S21, S32, S42 and S52 surfaces.

[0055] Table 2

[0056] surface k [alpha]4 [alpha]6 [alpha]8 10 ]]> ​ S12 0 7.748323E-10 -3.384737E-13 4.835538E-17 -2.526087E-21 S21 0 7.499271E-07 -1.956622E-10 2.027374E-13 -1.124624E-16 S32 0 2.310944E-07 2.281034E-11 -1.738637E-14 3.489336E-18 S42 0 1.460036E-06 -2.887830E-11 9.262144E-13 -1.351542E-16 S52 0 4.658763E-07 -9.094952E-11 -3.096278E-13 3.179701E-15

[0057] The binary diffraction surface involved in the S21 surface satisfies the following expression.

[0058] φ=A1ρ 2 +A2ρ 4

[0059] Where Φ is the phase of the diffraction surface, ρ=r / r n ,r n is the planning radius of the diffraction surface, and A1 and A2 are the phase coefficients of the diffraction surface.

[0060] Table 3 is the diffraction parameters of the S21 surface.

[0061] Table 3

[0062] surface r n ]]> [H1] [H2] H3 [H4] S21 28 -65.227663 -52.158309 111.337114 -56.805428

[0063] Figures 2-7The optical transfer function (42 lp / mm) corresponding to the large and small field of the optical system, the point column diagram, the field curvature and the distortion curve diagram. It can be judged from the figure that the optical system large and small field and the field of view, the aperture related axial spherical aberration, the vertical axis spherical aberration, the axial chromatic aberration, the vertical axis chromatic aberration, the coma, the field curvature, the distortion and the corresponding advanced aberration are well corrected, and the imaging is clear without obvious deformation.

[0064] In summary, the above is only the preferred embodiment of the present application, not for limiting the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A small F-number, double-aperture, double-field-of-view, uncooled long-wave infrared optical system, characterized in that: From the object side to the image side, along the optical axis and along the optical axis, the following components are included: a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a non-cooled long-wave infrared detector protection window; The first lens has positive focal power, its front surface is spherical, and its back surface is an even-order aspherical surface; the second lens has negative focal power, its front surface is a binary diffraction surface with an even-order aspherical base, and its back surface is spherical; the third lens has positive focal power, its front surface is spherical, and its back surface is an even-order aspherical surface; the fourth lens has positive focal power, its front surface is spherical, and its back surface is an even-order aspherical surface; the fifth lens has positive focal power, its front surface is spherical, and its back surface is an even-order aspherical surface; The second lens moves forward and backward along the optical axis to achieve magnification change between large field of view and small field of view; The even-order aspheric surfaces used by the first lens, the second lens, the third lens, the fourth lens, and the fifth lens satisfy the following expression: Where: z represents the distance from the vertex of the even aspheric surface to the height r along the optical axis, c represents the curvature of the surface vertex, k represents the cone coefficient, α4, α6, α8, α 10 Represents high-order aspheric coefficients; The binary diffraction surfaces used by the first lens, the second lens, the third lens, the fourth lens, and the fifth lens satisfy the following expression: Where: Φ is the phase of the diffraction surface, , r n is the planned radius of the diffraction surface, A1 and A2 are the phase coefficients of the diffraction surface; The large and small fields of view of the optical system have independent small F numbers, wherein the F number of the large field of view is 0.75 and the F number of the small field of view is 0.9; The optical system has independent small distortions for large and small fields of view, with the maximum distortion for the large field of view being -0.2% and the maximum distortion for the small field of view being 0.5%; The optical system has an effective focal length of 132 mm for a small field of view and a linear field of view of 9.84 mm; The effective focal length of the large field of view of the optical system is 66 mm, and the linear field of view is 9.84 mm.

2. The low F-number, double-aperture, double-field-of-view, uncooled long-wave infrared optical system according to claim 1, characterized in that: The large and small fields of view of the optical system have independent aperture positions, wherein the aperture surface for the large field of view is selected on the front surface of the third lens, and the aperture surface for the small field of view is selected on the front surface of the first lens.

3. The low F-number, double-aperture, double-field-of-view, uncooled long-wave infrared optical system according to claim 1, characterized in that: The first lens, the second lens, the third lens and the fifth lens are made of germanium material, and the fourth lens is made of IRG206 material.

4. The low F-number, double-aperture, double-field-of-view, uncooled long-wave infrared optical system according to claim 1, characterized in that: The uncooled long-wave infrared detector has a resolution of 640×512 and a pixel pitch of 12 microns.

5. The low F-number, double-diaphragm, double-field-of-view, uncooled long-wave infrared optical system according to any one of claims 1 to 4, characterized in that: The optical system operates in a wavelength range of 8 μm to 12 μm, with a central wavelength of 10 μm.

6. The low F-number, double-aperture, double-field-of-view, uncooled long-wave infrared optical system according to claim 5, characterized in that: The total optical length of the optical system is 186 mm.

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