A single-group mobile long-wave dual-field optical system integrating zoom and focus

Abstract

The present invention discloses a single-group mobile long-wave dual-field optical system that integrates magnification and focusing. From the object side to the image side, the system comprises a first lens, a second lens, a third lens, and a fourth lens connected in sequence. The first lens is a meniscus diffraction lens with positive focal length and a convex surface curved toward the object side. The second lens is a meniscus aspheric lens with negative focal length and a convex surface curved toward the object side. The third lens is a meniscus aspheric lens with negative focal length and a convex surface curved toward the object side. The fourth lens is a meniscus diffraction lens with positive focal length and a convex surface curved toward the image side. The first lens is a fixed group, and the second, third, and fourth lenses together form a mobile group. The present invention achieves field switching and focusing functions through the movement of a single group. The system has a simple structure, greatly simplifies the mechanical structure, reduces the difficulty of assembly and adjustment, and improves the stability and reliability of the system. The system consists of four lenses, with a small number of lenses, low cost, and high optical transmittance.

Description

Technical Field

[0001] The invention relates to a single-group mobile long-wave dual-viewing field optical system integrating magnification and focusing, and belongs to the technical field of long-wave dual-viewing field optical systems. Background Art

[0002] Infrared thermal imaging applications typically require an infrared optical system to simultaneously provide high-magnification images with a small field of view and low-magnification images with a large field of view to complete the system's target search, aiming, and tracking functions. The large field of view or low-magnification mode of a dual-field infrared optical system can be used to observe large areas and search for suspected targets, while the small field of view or high-magnification mode can be used to closely observe or magnify targets for identification, tracking, and aiming.

[0003] The existing long-wave dual-field optical systems mainly have three ways to achieve field of view switching: 1. dual linkage of zoom and compensation groups, 2. single-group mobile zoom, and 3. lens group cutting in and out.

[0004] The first type of dual-field optical system requires moving two lens groups to achieve field of view switching and one focus group to achieve focusing. It has a large number of mechanical moving groups and a relatively complex structure. This type of structure is the mainstream structure of existing long-wave dual-field lenses.

[0005] The second type of dual-field optical system has a relatively simpler structure than the first type, but has a smaller zoom ratio, which is usually less than or equal to 2x, and requires at least 5 lenses. This requires a large number of lenses, is bulky, and is more expensive. Therefore, this type of structure is rarely used in the market.

[0006] The mechanical switching of the third method is more complicated, and generally long-wave dual-field lenses do not use this type of optical system.

[0007] To this end, the present invention provides a long-wave dual-field optical system with four lenses moving in a single group, which integrates magnification and focusing, greatly simplifies the mechanical focusing structure, increases the stability and reliability of the system, and has the advantages of low cost, good image quality and good stability. Summary of the Invention

[0008] The present invention provides a long-wave dual-field optical system that integrates magnification and focusing with a single-group movement. It uses four lenses and realizes field switching and focusing simultaneously through a single-group movement, which is simple, reliable and stable.

[0009] In order to solve the above technical problems, the technical solutions adopted by the present invention are as follows:

[0010] A single-group mobile long-wavelength dual-field optical system integrating zooming and focusing, comprising a first lens, a second lens, a third lens, and a fourth lens connected in sequence from the object side to the image side;

[0011] The first lens is a meniscus diffraction lens with positive optical power and a convex surface curved toward the object side;

[0012] The second lens is a meniscus aspheric lens with negative optical power and a convex surface curved toward the object;

[0013] The third lens is a meniscus aspheric lens with negative optical power and a convex surface curved toward the object.

[0014] The fourth lens is a meniscus diffraction lens with positive refractive power and a convex surface curved toward the image side;

[0015] Among them, the first lens is a fixed group, and the second lens, the third lens and the fourth lens together form a moving group.

[0016] As mentioned above, from the object side to the image side, the first lens is a fixed group, and its relative position remains unchanged. The second, third, and fourth lenses together form a moving group and move as a whole (that is, this application only has one moving group) to achieve switching from a wide field of view to a narrow field of view and keep the image plane stable. Compared with the traditional dual-field objective lens, the traditional dual-group linked zoom dual-field lens generally requires three moving groups. There are many moving groups, and there are many variables that affect the optical axis offset. The optical system of this application does not have a compensation group to adjust the focal plane position drift caused by the zoom, which simplifies the zoom form. At the same time, by expanding the travel of the moving group and reserving the focus margin, it is possible to focus on targets at different positions at different distances. There is no need to add a separate focusing group, and the zoom and focusing of the dual-field lens are combined into one, thereby further simplifying the optical system, simplifying the mechanical structure, and easily controlling the optical axis drift. It has the advantages of low cost and good optical stability in application fields such as electrically adjusted observation and manual aiming.

[0017] The operating band of the above-mentioned single-group mobile long-wave dual-field optical system is 8um~12um, the field of view angles are 17.5°×14° / 5.8°×4.6° respectively, and the corresponding optical apertures are F#1.0 / F#1.2 respectively.

[0018] The materials used for the first lens, the second lens, the third lens and the fourth lens are all germanium.

[0019] In order to further improve the imaging quality, let the focal length of the first lens be f1, the focal length of the second lens be f2, the focal length of the third lens be f3, the focal length of the fourth lens be f4, and the wide field focal length of the single-group moving long-wave dual-field optical system be F, satisfying the following relationship:

[0020] 1.6F<f1<1.8F; -1.1F<f2<-1F; -1.4F<f3<-1.3F; 0.7F<f4<0.8F.

[0021] From the object side to the image side, the two surfaces of the first lens are sequentially called the first object-side surface and the first image-side surface, the two surfaces of the second lens are sequentially called the second object-side surface and the second image-side surface, the two surfaces of the third lens are sequentially called the third object-side surface and the third image-side surface, and the two surfaces of the fourth lens are sequentially called the fourth object-side surface and the fourth image-side surface;

[0022] To further ensure the imaging effect, the curvature radius of the first object-side surface is 46.8700±0.0030mm, and the curvature radius of the first image-side surface is 62.9496±0.0030mm;

[0023] The curvature radius of the second object-side surface is 35.8700±0.0030mm, and the curvature radius of the second image-side surface is 26.9986±0.0030mm;

[0024] The curvature radius of the third object side is 28.8330±0.0030mm, and the curvature radius of the third image side is 23.4170±0.0030mm;

[0025] The curvature radius of the fourth object-side surface is -88.7486±0.0030 mm, and the curvature radius of the fourth image-side surface is -37.1057±0.0030 mm.

[0026] The first image-side surface and the fourth image-side surface are both diffraction surfaces, and the second image-side surface, the third image-side surface and the fourth object-side surface are all aspherical surfaces.

[0027] To further improve the integrity of the quality, the center thickness of the first lens is 8.76 ± 0.03mm, the center thickness of the second lens is 1.20 ± 0.03mm, the center thickness of the third lens is 1.00 ± 0.03mm, and the center thickness of the fourth lens is 5.62 ± 0.03mm. The center spacing between the first and second lenses is 7.15 ± 0.03mm or 22.70 ± 0.03mm, the center spacing between the second and third lenses is 3.90 ± 0.03mm, and the center spacing between the third and fourth lenses is 20.85 ± 0.03mm.

[0028] The technologies not mentioned in this invention are all referred to the prior art.

[0029] The present invention has the following beneficial effects:

[0030] 1. The present invention integrates zooming and focusing into a single-group mobile long-wave dual-field optical system. It realizes field switching and focusing functions through a single group movement. It has a simple structure, greatly simplifies the mechanical structure, reduces the difficulty of installation and adjustment, is conducive to controlling the system optical axis drift, and improves the stability and reliability of the system.

[0031] 2. The single-group mobile long-wave dual-field optical system of the present invention integrates zooming and focusing, and is composed of 4 lenses, with a small number of lenses, low cost and high optical transmittance.

[0032] 3. The single-group mobile long-wave dual-field optical system of the present invention integrates magnification and focusing, has a large magnification ratio, and can be used for long-wave dual-field objective lenses with a magnification ratio of ≤3 times. By simplifying the zooming and focusing methods and reducing the number of lenses, it is beneficial to reduce the weight of the entire machine. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a schematic diagram of the principle of a single-group mobile long-wave dual-field optical system that integrates zooming and focusing in the present invention;

[0034] Figure 2 This is a schematic structural diagram of a single-group mobile long-wave dual-field optical system integrating zooming and focusing in the present invention;

[0035] Figure 3 This is a wide-field transfer function curve diagram of the single-group mobile long-wave dual-field optical system integrating zoom and focus adjustment of the present invention;

[0036] Figure 4 This is a graph showing the narrow field of view transfer function of the single-group mobile long-wave dual-field optical system integrating zooming and focusing according to the present invention;

[0037] Figure 5 This is a graph showing the wide field curvature and distortion of the single-group mobile long-wave dual-field optical system that integrates zooming and focusing.

[0038] Figure 6 This is a graph showing the narrow field curvature and distortion of the single-group mobile long-wave dual-field optical system that integrates zooming and focusing. DETAILED DESCRIPTION

[0039] In order to better understand the present invention, the following embodiments are provided to further illustrate the present invention, but the present invention is not limited to the following embodiments. The accompanying drawings are provided for reference and illustration only and are not intended to limit the present invention.

[0040] Example 1

[0041] like Figure 1-2 As shown, a single-group mobile long-wavelength dual-field optical system integrating zooming and focusing, comprising a first lens, a second lens, a third lens, and a fourth lens connected in sequence from the object side to the image side;

[0042] The focal lengths of the first to fourth lenses are f1, f2, f3, and f4, respectively. The wide-field focal length of the single-group moving long-wavelength dual-field optical system is F, with a specific value of F being 25 mm. Each lens has the following characteristics:

[0043] The first lens L1 is a diffractive lens with positive refractive power and a concave diffraction surface, with f1 less than 1.8F and 1.6F less than 1.8F.

[0044] The second lens L2 is a single aspheric meniscus lens with negative optical power and a convex surface facing the object; -1.1F<f2<-1F;

[0045] The third lens L3 is a single aspheric meniscus lens with negative optical power and a convex surface facing the object; -1.4F<f3<-1.3F;

[0046] The fourth lens L4 is a diffractive lens with positive refractive power and a convex diffraction surface, with an aperture of 0.7F < f4 < 0.8F.

[0047] In this example, f1 is 43.25mm, f2 is -26.11mm, f3 is -33.39mm, and f4 is 18.96mm.

[0048] Table 1 shows the technical indicators of the single-group mobile long-wave dual-field optical system integrating zooming and focusing in this embodiment, Table 2 shows the specific optical parameters of the single-group mobile long-wave dual-field optical system in this embodiment, and Table 3 shows the specific aspheric coefficients used in the single-group mobile long-wave dual-field optical system integrating zooming and focusing in this embodiment.

[0049] Table 1 Technical indicators of optical system

[0050]

[0051] Table 2 Specific optical parameters of the optical system:

[0052]

[0053]

[0054] In Table 2, "Radius of Curvature" refers to the radius of curvature of each lens surface, "Thickness" or "Separation" refers to the lens thickness or the center-to-center spacing between adjacent lens elements, "Material" refers to the lens material, and "Air" refers to the space between the two lenses containing air. The first lens L1 has two surfaces: the first object-side surface S1 and the first image-side surface S2. The second lens L2 has two surfaces: the second object-side surface S3 and the second image-side surface S4. The third lens L3 has two surfaces: the third object-side surface S5 and the third image-side surface S6. The fourth lens L4 has two surfaces: the fourth object-side surface S7 and the fourth image-side surface S8.

[0055] Table 3 Aspheric coefficients used in specific embodiments

[0056]

[0057] The aspheric equations used for each surface in Table 3 are:

[0058]

[0059] The meanings of each quantity are as follows:

[0060] ZA: lens sagittal height of the aspheric surface along the optical axis;

[0061] R: radius of curvature at the intersection of the surface and the optical axis OO';

[0062] Y: semi-aperture of the lens perpendicular to the optical axis;

[0063] k: cone coefficient;

[0064] A, B, C, D aspheric coefficients

[0065] Table 4 Diffraction coefficients of S7 surface

[0066]

[0067]

[0068] The diffraction surface equation used in Table 4 is:

[0069] Φ=A1Y 2 +A2Y 4 +A3Y 6

[0070] in:

[0071] Φ: phase of the diffraction surface;

[0072] Y: semi-aperture of the lens perpendicular to the optical axis;

[0073] A1, A2, and A3 are the diffraction surface phase coefficients.

[0074] Figure 3 is the transfer function curve of the optical system with wide field of view of the present invention, Figure 4 The transfer function curve of the optical system with narrow field of view of the present invention is shown in FIG. Figure 3 、 4 It can be seen that the 42lp / mm transfer function values ​​are close to the diffraction limit, and the values ​​are all greater than 0.3, indicating excellent image quality. Figure 5 The field curvature and distortion curves of the wide field of view of the present invention are shown in FIG. Figure 6 The field curvature and distortion curves of the narrow field of view of the present invention are shown in FIG. Figure 5 、 6 It can be seen that the field curvature of the wide and narrow fields of view of the present invention is less than 0.1 mm, and the distortion is less than 2%. The distortion is small and the image distortion is small.

Claims

1. A single-group mobile long-wavelength dual-field optical system integrating zoom and focus adjustment, characterized by: The optical system has four lenses, which include a first lens, a second lens, a third lens, and a fourth lens connected in sequence from the object side to the image side; The first lens is a meniscus diffraction lens with positive optical power and a convex surface curved toward the object side; The second lens is a meniscus aspheric lens with negative optical power and a convex surface curved toward the object; The third lens is a meniscus aspheric lens with negative optical power and a convex surface curved toward the object. The fourth lens is a meniscus diffraction lens with positive refractive power and a convex surface curved toward the image side; Among them, the first lens is a fixed group, and the second lens, the third lens and the fourth lens together form a moving group; The focal length of the first lens is f1, the focal length of the second lens is f2, the focal length of the third lens is f3, the focal length of the fourth lens is f4, and the wide field focal length of the single-group moving long-wave dual-field optical system is F, which satisfies the following relationship: 1.6F<f1<1.8F; -1.1F<f2<-1F; -1.4F<f3<-1.3F; 0.7F<f4<0.8F.

2. The single-group mobile long-wavelength dual-field optical system integrating zoom and focus adjustment according to claim 1, characterized in that: The operating band is 8um~12um, the field of view is 17.5°×14° / 5.8°×4.6°, and the corresponding optical apertures are F#1.0 / F#1.

2.

3. The single-group mobile long-wavelength dual-field optical system integrating zoom and focus adjustment according to claim 1 or 2, characterized in that: The first lens, the second lens, the third lens and the fourth lens are all made of germanium.

4. The single-group mobile long-wavelength dual-field optical system integrating zoom and focus adjustment according to claim 1 or 2, characterized in that: From the object side to the image side, the two surfaces of the first lens are sequentially called the first object-side surface and the first image-side surface, the two surfaces of the second lens are sequentially called the second object-side surface and the second image-side surface, the two surfaces of the third lens are sequentially called the third object-side surface and the third image-side surface, and the two surfaces of the fourth lens are sequentially called the fourth object-side surface and the fourth image-side surface; The radius of curvature of the first object-side surface is 46.8700±0.0030mm, and the radius of curvature of the first image-side surface is 62.9496±0.0030mm; The curvature radius of the second object-side surface is 35.8700±0.0030mm, and the curvature radius of the second image-side surface is 26.9986±0.0030mm; The curvature radius of the third object side is 28.8330±0.0030mm, and the curvature radius of the third image side is 23.4170±0.0030mm; The curvature radius of the fourth object-side surface is -88.7486±0.0030 mm, and the curvature radius of the fourth image-side surface is -37.1057±0.0030 mm.

5. The single-group mobile long-wavelength dual-field optical system according to claim 4, characterized in that: The first image-side surface and the fourth image-side surface are both diffraction surfaces.

6. The single-group mobile long-wavelength dual-field optical system integrating zoom and focus adjustment according to claim 4, characterized in that: The second image-side surface, the third image-side surface, and the fourth object-side surface are all aspherical.

7. The single-group mobile long-wavelength dual-field optical system integrating zooming and focusing as claimed in claim 1 or 2, characterized in that: The center thickness of the first lens is 8.76±0.03 mm, the center thickness of the second lens is 1.20±0.03 mm, the center thickness of the third lens is 1.00±0.03 mm, and the center thickness of the fourth lens is 5.62±0.03 mm.

8. The single-group mobile long-wavelength dual-field optical system integrating zooming and focusing as claimed in claim 1 or 2, characterized in that: The center distance between the first lens and the second lens is 7.15±0.03 mm or 22.70±0.03 mm, the center distance between the second lens and the third lens is 3.90±0.03 mm, and the center distance between the third lens and the fourth lens is 20.85±0.03 mm.

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